Have many out there got 7.62mm L4 guns? Or will I be wasting my time putting L4 stuff on the Forum?
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Have many out there got 7.62mm L4 guns? Or will I be wasting my time putting L4 stuff on the Forum?
It's only a de-ac' but I've a ex Kiwi L4A4. Always interested in hearing about them and especially their accesories .
ATB
Tom
Mine goes bang! Please do tell!!
.....well, I'd be interested. And appreciative.
-TomH
Keep it ALL coming Peter. I personally, have Two L4A4's & an EX SA Converted MKII to 7.62mm. Also a lot of tools & accessories for the Range of L4's.
I NEED a GENUINE L4A3 for the Collection. there are a few made up examples about. But these have been done by a private individual. Not at Enfield. Or a Genuine Ordanance Factory/Workshop............
Well all mine go click but don't go bang unfortunately,
I've got an A2 to A4, an Ex NZ A4, an A3, an IMG15GA and IMG16GA so I'll absorb all the info you have.
QUITE Happy to swap a Genuine A4 for a GENUINE A3!.............;)
Before I go on with this bit/thread, a question............ Is anyone out there in forumland contemplating the conversion of a standard Mk2 or 3 Bren into a repro, live or dewat/deact L4 look-a-like project?
Yes please Peter always worth storing in the memory banks...........and you you know my old adage "Pass it on before you leave":lol:
Well chaps, I did ask and you said yes, so here goes. This isn't a technical article as such, just describing the pitfalls and suchlike. It would be very easy to go beyond the point of no return if you were doing the real McCoy so this is aimed at converting a deact/dewat. Here goes........, and thanks to the several unamed who helped along the way.
A very timely question was raised by a former a week or so ago regarding the conversion of a .303” Bren to L4A2 on spec. I have been on just such a quest for the past what seems like an eternity weeks or so! And I know that another UK forumer has done/tried/attempted/partially failed something similar in the past so I hope he will chip in too…….
The very first thing I’d have to say is, well……., don’t bother yourself! It is excruciatingly difficult, even with a reasonably well equipped machine shop. And I didn’t want anything that was a rock and roller or even a - shooter, just a good to the point of externally indistinguishable repro. To be honest, I had most of the engineering drawings and had seen/remembered more about these L4’s than I care to think about. To be honest, the drawings seem to relate to something different and the machining doesn’t relate to the inserts and the inserts……….. And on and on it goes. To be honest and frank I do not believe anyone who states that he HAS successfully converted a .303” Bren to a live fire 7.62mm L4 Bren. I would clarify this by lowering the standard to say that not only a live-fire L4, but one that will function with drill rounds and conform to the basic gauge specs too. Anyone prepared to accept the challenge?
How Enfield ever fitted the new spaced ejector block/magazine catch with the drawings they were supposed to be working with is just beyond me. My only saving grace was that I was intimately involved with the fundamentals of both the Bren I was using and the L4 that I hope to achieve. Or as one wag suggested, were the drawings so ambiguous that they’d effectively prevent another nation from doing this and keeping the work in-house might be the very reason for the difficulties in deciphering them!
The problems start with deciding WHAT you’re going to start with. If you are in the UK and starting with a standard UK spec dewat/deact then the very first problem is stripping it down carefully. I won’t go into the niceties of it but it came apart and the almost immediate further machining quickly meant that it was now even FURTHER deactivated to the point of even MORE totally inert than when I started! I would venture to suggest that the internal machining you are about to undertake to the body is so severe that any notion that you are effectively making or converting it into something fireable or useable is ridiculous and would not need re-certifying. Just my opinion based upon my experience. If you start with a bog standard but expensive Mk3 gun then the problems are just about to start. You’ve got to get yourself a ‘new’ barrel and that could be a BIG hurdle/headache. Because in short, the Mk3 gun barrel is too short and light to convert to the later A2,3,4,5 gun spec so you have to start with a Mk2 barrel and set about machining that down to a) length and b) diameters. I stripped mine completely and the gas block came off quite easily. Then when it’s all machined, align EXACTLY square the new pronged flash eliminator. These seem easy to acquire.
To be honest, the steel quality of the barrels ensures that it cuts like a dream. If you are starting with a Mk2 barrel, here’s the basic dimensions for the two later type barrels as fitted to the A2 to A5 guns. Main rear diameter up to the carrying handle should remain the same as it is. The second and third sections, up to the and past the locating section (that seats just to the rear of the blast shield) should be machined down to .910 and the diameter from the gas block forward is to remain the same, at .870” or thereabouts. This section must be reduced in length to give a barrel length from the gas block forward of 5.4”. The total barrel length of the L4 barrels being 21” or 24” including the fluted flash eliminator that is sleeved over the muzzle section. If you are doing an L4A1, then the diameters are as for the Mk3 gun barrel but the length is 24” overall, as the A2 gun barrel. Don’t forget to machine the flash eliminator to suit too!
I decided to use a Mk2 gun so the first thing was it had to be converted to Mk2/1 spec with the ‘hump’ used to stop the cocking handle from reciprocating being machined off and the new block to accommodate the old Mk1 type folding cocking handle brazed and pinned in place. This is not the case with ALL L4A3’s and 5’s and the A5 Navy BR parts list clearly identifies both cocking handles as ‘A/R’ indicating ‘as required’. I chose to. I started to follow the drawings for the new ejector block but these drawings were clearly done by a fluent Swahili writer….., somewhere! Eventually I just followed my nose and milled carefully until the new ejector block fitted well and could be locked in by the pin. This ejector retaining pin is an important datum
Likewise with the front of the magazine well. The drawings were not a lot of help. This time I can only presume, because they were formulated to use while the body was canted at suitable cutting angles. So I did it by eye by doing this…… I took an old L1A1 rifle magazine and un-brazed the front locating lug (you could use an old alloy FN rifle magazine and dolly the small knib flat….). Then carefully machined the edges of the magazine well parallel from about half way along the opening, forwards. Then forwards and down into the front face of the well so the magazine would lock at the rear, sit square to the horizontal body and JUST clear the remains of the body feed lips. To do this, you’ll need to mill out the magazine well to the depth of the slave magazine that you’re using. That means totally removing the old .303” Bren magazine lip supports. Lastly by careful calculation I machined away the undercut for the magazine front locating lug.
Inserted ‘stop/support’ pin for the body locking nut plunger spring after cutting 3 coils off the spring. I couldn’t even start to decipher the drawings to locate the two body inserts so accurately positioned them from drawings taken from an L4A4 gun!
The next thing you’ll find is that when the magazine is fitted, the old .303” breech block will not rise fully to lock-up behind the locking shoulder. This is due to the fact that the new geometry of the deeper seated magazine due to…… and…….. and….. The answer is to convert the breech block to 7.62mm spec by grinding the top outer surfaces, the surfaces astride the feed horns (and grind them off parallel with the front face of the block while you’re there too…….) so that they are clear of the new 7.62mm rifle or Bren magazine lips and allow the breech block/piston extension and post to reciprocate freely without interference from the new magazine lips
If you want to go ballistic you could (I did, just to show willing) convert the carrying handle sleeve 21 hole Mk3 variety specified for the L4 guns (although we didn’t worry too much about these trivial niceties in the real world I have to admit!) and fit a Mk2 type parallel carrying handle
Next is the fitting of the Mk3 lightweight butt slide and butt assembly……… Haven’t got them? Well you can easily convert the butt slide but suggest that you scan the internet or elsewhere for the butt, butt plate and fittings. The butt plate……, yes……. And don’t forget that this must be modified to incorporate a sling loop at the top. And if we’re getting pedantic, don’t forget that the L4’s were modified in service with a ‘double sear’ across the piston post. L4/all Mk3 bipod sleeve with a gas shroud is a direct fit.
Bar out all old and engrave bodyside with new designation and add new UE type number
Would I do it again – or even bother……. An emphatic NO! But does it look good. Yes!
This is what you’re going to need. Mk2 or 3 gun
L4 bipod sleeve blast shroud or use an L4 bipod sleeve assembly
Modified Mk3 butt plate (easy to do)
L4A2 magazine catch assembly
Machine piston extension and piston post to ‘safe’ spec
Pete, Im going to go the easy route. Use a MKII Gun, & convert to L4A3 Spec. I have Two L4A4's, so can use one as a 'Reference' Pattern. To measure & copy exactly, the internal machining specs. ;)
When you say, L4A2 Mag Catch Assembly. Did Mean to say Ejector BLOCK Assy. Rather than Catch?....;)
Oooooops....... Yes, ejector block assembly. One thing I did forget to mention was to remove the two protruding what we called 'stop blocks' from the left and right rear face of the old .303" Mk2 barrel. The new 7.62mm barrel face must be flat. And don't forget that to be 'original' you'll need to put the red oblong with 7.62 on the bodysides too.
One thing I did notice that I'd never noticed in service was the variety of dimensions with the magazines. Not noticeable with the rifle as they don't fit into a full all-enclosed mag well. But with a Bren, you can have very loose to very tight.
And here's something else about the L4 conversions. As you are probably aware, during the actual conversion process, the butt slide that came IN with the body, wasn't necessarily the butt slide that went OUT with the body. So even if you can see the old LB serial number, they won't necessarily be matched.
If you can see a small triangle next to or close to the new UE serial number, that means the body was crack tested while in its white metal stage, prior to being machined. This was because while in its 7.62mm guise, it was discovered that the old Mk3 bodies (but not the old Mk2 bodies incidentally) were really at the limit of their absorbent linear strength. As a result the bodies were ND crack tested.
Due to financial constraints, nothing was wasted from the 'waste' removed from the Mk3 guns. Mk3 barrels that conformed to the Base Workshop standard were returned to the RSSD for repackaging and return to Ordnance stockpiles for future use. As for the old barrels, the complete carrying handle assemblies were simply transferred over to the new made 7.62's. And in case you think that was a bit penny pinching, then next time you see an L4, look at the gas blocks too. Because where these were serviceable, then they were removed and fitted to the new barrels too. After all, if you are boring the gas hole through a new gas block and 7.62mm barrel (yes, they are drilled after assembly and alignment) then it's a simple matter to simply align and partially bore using an existing part-used gas block. Waste not, want not as they say.
And if that wasn't enough, even the original magazine opening cover was 'cut-and-shut' to fit with an additional part inserted and brazed in place. Like the gas block on the barrel, take a look at the 'new' bipod sleeve - the part that slides onto the gas cylinder. This is different on the L4 guns as it now includes a gas blast shield/cover. But once again, if the bipod sleeve was serviceable, the old sling loop was machined off, ground to size and the blast shield/cover was brazed into place. The Bipod sleeves are a good way to see the old manufacturers markings including MA, JI, CRD, BSA, DE and many others. Once again, waste not, want not.
The old breech blocks were collected up and sent to a specialist recycler for their high value and known chrome steel content. No financial return as such but the INCOMING blocks of the same material for the new 7.62mm breech blocks was delivered from the steel makers at a trade-off price.
More later................
Nothing
Here is my successful conversion of a MKII to an L4A3. Many thanks to Kev who helped with info and parts along the way.
it works - YouTube
Inserts
gas shield
overall - still waiting on my Gorton 3U to be delivered to properly engrave. Just noticed this is an older pic as the gas shield had not been replaced with the proper one.
Bren MKII 54r conversion
20141021 180452 - YouTube
The real knack is to master the double tap on a continuos basis :thup:
Well, the first video shows that you CAN do it! You can't get any more conclusive than that. I have to say that the internal machining defeated me. I say 'defeated'..... in that it worked superficially but only due to prior knowledge.
The front of the magazine well defeated the Design Office at Enfield at first until someone had a brain-wave. They slit a body right down the centre line in a 'one picture describes a thousand words' sort of way. That way a picture emerged of the TRUE problem and within hours, the solution was found to yet another seemingly impossible hurdle. A small pin to act as a stop in the barrel nut plunger spring hole.
Good work C130 and thanks for the video........
Is that an early L4A1 type flash eliminator on the L4A3 conversion C130? These were weak at the heavily tapered muzzle end and were prone to splitting the prongs. Same as old and well worn/used L1A1 rifle flash eliminators used to do eventually. Nice to see an L4 singing for its supper. We could always tell the different Brens when you had mixed ranges. The old Brens made a gentlemanly pop-pop-pop-popping sound while the big bad L4's just went banging away........... for want of a better word!
I will have to rely on your knowledge for the barrel/flash hider id.
That's the real McCoy L4 later barrel with stronger flash eliminator and reinforced breech end. What finish is that on the main body? Just white bead blasted metal awaiting phosphate and paint/engraving or another finish. Brian at BDL can do exact UK Military finish.
I just need to see the video again to get my daily fix of L4's........
Correct. Just in the white bead blasted. There was no point in finishing until the engraving is done. You wouldn't happen to know/have the font would you? I talked with Brian in the past and unfortunately he led me to believe his Suncorite supply is very low and he was saving it for his own projects.
that paint is available now and then. there was a guy selling 1 litre cans for 20 quid in the uk
but its hazmat and illegal to import! :(
I think that you might find Brian abit more sympathetic now he's seen what you've done - and done so damn well! The font...... Ask Brian to do a pencil/tracing rubbing of his markings or a good close-up photo of the markings against a scale. He might have an original A3 as I understand.
Did you modify the butt slide too C130? Not that it makes any difference. Some of the foreign nations on a budget just sent in, say, 100 gun bodies and got 100 L4A3 bodies and matching/numbered breech blocks back to reassemble to the almost scrap and worn out butt slides and bipod assembliess that they had taken off earlier. Mind you, those equally hard-up almost bankrupt African nations that were on an aid budget from the benevolent UK just sent in complete scrap Brens in and got almost new, factory fresh L4A3's. Ghana being one such..... Oh, don't get me going...........
The bipod assembly was purchased from Kevin. Kevin also supplied me with pencil rubbings. With luck, the Gorton 3U will be here in a month. It's paid for but the logistics of shipping from Connecticut to Virginia is hampering things bit. The butt slide, I am unsure what mods were to be accomplished. Do you care to shed some light on those mods?
c310, I managed to scrounge some more Suncorite 259 since we last spoke.
Hey......, there you go. The power of the Forum for you C130! The original Mk2 butt slide side walls were reduced in thickness to .6" from the radius, and radiussed deeper, immediately in front of the trigger guard, milling forward to a similar radius, ending and almost following the front radius at the front end of the ejection opening. Effectively converting the Mk2 butt slide into a Mk3 gun lightweight butt slide. Additionally the bolt type Mk2 pistol grip retainer was converted to the Mk1 or 3 type using the hollow large diameter bolt with a new threaded sleeve brazed in place.
The reason in UK Military service was in the interests of standardisation with the existing Mk3 and L4A2 and 4 guns of course
But, hey....., with what you have done so far, this is just cosmetic stuff! And I doubt that the export buyers bothered with this
Well that's easy enough. It was built on a lower with the MKI type handle. I have a MKIII I can basically copy the contours off of and presto. I will have to give Brian a call on Monday and see if we can't work something out. Thanks guys.
If you're starting with a Mk1 butt slide then don't forget to shorten the front 1" or so, as per the Mk3 gun type you are copying. Great work so far. If I hadn't seen it, I wouldn't have believed it after my experience doing the same!
Maybe just caught up on something internally as it should remain forward under the control of the spring loaded plunger in the cocking handle. Worn spring plunger and the little vertical cam-pin. They get flats worn on them
Harry mac, I enjoy mine, (Inglis Mk.II and Enfield L4A3). They are both post '86 dealer samples since I can't afford to shell out $25-30K for a transferrable one. I feel lucky to have them even though they are government rentals more of less!
Yes, I have noticed that also. That's Joe's transferable converted/ running 54r. It was test day and on the lowest gas setting it was still way to much. It also has the MKI single return spring. A MKII spring has since been installed and we are trying to figure out how to choke the gas down more. Evidently the mag didn't run as we'll at the Marietta shoot so back to the drawing board. If I could get my hands on some factory drawings for the 303 mag it would be helpful. We want to modify the follower and having the original geometry of both mag and follower would be very helpful. Peter?
---------- Post added at 06:07 AM ---------- Previous post was at 06:04 AM ----------
Sorry Brian, it's been chaotic. Wife's been traveling, I am an airline pilot, so with two little ones it's been crazy. Beautiful pics you sent me last week. I now want an L1. Any word from your engraving buddy?
I don't have magazine drawings but given the availability of magazines and platforms, the actual feeding geometry shouldn't pose too much of a dilemma if you use a few platforms to practice with. The only 'problem' I can see is with the fact that the round is slightly shorter than standard so there is a longer what we call 'no-mans land'. That is the time that the round is being pushed forwards IN the magazine until noses out it is cammed downwards and left or right and into the chamber.
The 'problem' as I would see it is that because the 7.62R rim is much thinner, it is sat inside the same depth cartridge seating in the bolt and therefore the now tightened up (by the extractor stay don't forget.....) extractor cannot exert the same leverage on the rim while the breech block is rotating downwards to unlock. In short, and cutting out the crap and waffle, you're short of most of the primary extraction.
If I had to reduce the excessive 762R gas, this is what I'd do - to a spare barrel first. Drill and tap the gas port slightly oversize. Insert a hexagon headed grub screw with a slightly smaller hole bored through, making sure of course that it is well clear of the bore of course. Back it off until it allows you to insert the gas regulator which will initially support the new undersize vent. Now test fire, adjusting the 'new' gas hole in assorted modified grub screws until it runs well on gas regulater hole 2. Leave it there and within a few more test firings it will be rock solid. (added a bit later..... There is a LOT of meat on all of the barrels at this point, certainly enough to drill and tap. Additionally, this part is also reinforced by the gas block sleeved on too don't forget
The last part is to never tell anyone that I suggested this dire, seemingly bubba course of action! But the only way to get less gas is to look at Boyles law s of gas. All you are doing is what everyone who uses blank firing weapons does every day. We used to have a couple of blank firing AK47's and an assortment of different sized apertures in the various BFA's.
As a matter of interest C130 Pilot. I've heard of a C-130 and jumped out of one 26(?) times, - but what is a C-310?
C310,
IMO if you need less gas then you have to modify the holes in the regulator. The regulator has to be annealed to drill it. If you modify the barrel inlet the gas regulator will only work for the holes that are smaller than the inlet. If the inlet hole is smaller than the #1 reg hole the regulator will have no effect on gas pressure, at least that's my opinion.
On the Bren mag issue, I doubt modifying the follower on a Bren mag will help using the 7.62 x 54R. The modification of the ZB39 mag to run 7.62 x54R , including the one you were using essentially includes a helper spring to point the bullet tips up after about 12 rds. In order to maintain the high capacity the orig. mag spring is weakened so that the at capacity the total force of the helper and orig. mag spring are close to the orig. spring or the first rds. can't be stripped. That leaves later rds. (below about 12) with a weaker than design spring. It's all a compromise because the mag case does not have the right geometry (Radius) for 7.62 x 54r round.
Below is a summary of the single stack angle (actual mag is double but the proportions should hold) and the inside radius of the mag.
Magazine/cartridge---------- Stack Angle ---------- Magazine Inside Radius
.303 British Bren ------------ 9.78 ------------------ 6.31"
7.62x 54R ---------------------- 5.38 -------------------- ?
8x56R ZB39---------------------- 3.92 ------------------- 10.0"
You can see from the above table why the ZB39 mag is useful for the 7.62x54R because the stack angle is much closer to 7.62 x 54r than the Bren. When you put 54R in the Bren they start pointing up as more rds. are loaded. On the ZB39 they point downward which is much easier to counter with a helper spring.
Using the above table and the stacking angles you can predict an inside radius for a 54R mag of about 9".
Awhile back some pics. were posted of North Korean PKM's with hi capacity 54R box mags. Scaling the pic and making some reasonable assumptions since I doubt Kim Jung Il will send us one I came up with a inside radius of about 9". The pic is attached below.
IMO to get a 54R mag that really works you will need to design the mag case geometry to fit the 7.62x54R round. Helper springs, follower mods won't do it.
Joe
Attachment 57919
c310, He can do it. Just waiting on you.
Good afternoon Joe. Good technical points and really got the grey matter ticking over............ Re the gas port in the barrel situation, I see the point. That a larger hole further down the gas passageway will have no effect in a physics theory lesson but in a situation like a Bren, we have to remember that the gas being delivered is an explosive force as opposed to a sustained 'push' such as you'd get in , say, a steam engine or even a high performance car engine. Here we have an impulse force which delivers almost mind blowing accelleration to the piston and with it, the associated inertia/momentum. And it's this momentum that we really want to control. And you HAVE to control/reduce it before it gets to the piston
Re the magazine. Mmmmmmmmmm. Perhaps the most difficult part of any weapon to design and even MORE difficult to get right! An apprentices classroom discussion about just this subject could go on for weeks but here goes....... At the end of any travel DOWN the magazine, however the rounds manage this, the only point that matters is that the top round in the magazine (the round waiting to be fed) must momentarily be positioned EXACTLY in the same position of the previously fired round and all of the other rounds before that. If not, it's doomed to fail. All that we need is for that round to be presented at the correct angle downwards and inwards and it will (?) work/feed...... yes?
I've never converted a .303 mag to 762R so I am theorising that the magazine radius of/for the requirement between the two rounds is marginal and even less so because they are double stacked. Thus, with a bit of titivating or perhaps adding a slightly more pronounced downward 'wedge' effect to the front of the platform should take up the slack so to speak.
This can work as the mag platform is able to 'articulate'* to some degree within the magazine so this should be able to cater for what's needed. After all, the good quality HK .;22" rifle magazines do a more difficult job really well.
* 'articulate' is the wrong word as it can't articulate as it's solid but I can't think of another word to express what I mean. Maybe 'level itself out' or 'able to accommodate' might be a better choice.
Hi Peter,
Can't argue with your theory on the gas because I haven't tried it. Here in the US were are stuck with semi-auto unless we have a very large "Toy budget". I've found that my Bren's , a Mk I & MkII both require a #3 and for total reliability a #4 gas setting. I redid the barrel inlet, regulator holes and outlet holes in a .303 barrel so that the #2 setting was equivalent to an original # 4 setting. I haven't had a chance to try it out yet.
I've have no first hand info on full auto. Unlike C310 FA 54r Bren my semi-auto 54R runs about the same as .303 British requiring a 3 o4 setting?
The info I posted about the mags. was a result of my research trying to build a 25 rd. 7.62x54R using a ZB39 mag. It does work with semi auto but I had my doubts about FA due to speed and reduced spring tension. I previously posted the details on this Board. I have tried to "articulate" the follower only to have them jam about halfway thru the mag. You are definitely right about the round being at the right position for the bolt to grab it. A fixed follower won't work.
On the other hand if you grind down the horns on ZB39 follower and remove the follower guide so that the follower can freely rotate the mag will work with a 7.62 x51 Nato . The difference being that you are dealing with a almost 0 stacking angle rimless case. The steep rimmed cases seem to be the culprit.
I've attached a pic of 17 rds. of 54R in a .303 Bren mag. First round is fine as rounds are added they rotate. If you eliminate the follower guide so that the follower can rotate they will at some point jam. The ZB39 mag is just the opposite at about 12 rds. they point down and don't clear the lip.
It would sure be great if someone could come up with an easy solution but so far I haven't heard of any.
Attached are pic of 17 rds. of 54R in a unmodified Bren mag & a unmodified ZB39 mag. Bren on right.
Joe
Attachment 57924Attachment 57925
Peter, the C130 is a great airplane. Unfortunately the Cessna 310 could sit on the C130's elevator! It's a small twin engine 6 seater. I owned a 61' 310 F model long ago. The username is a carry over from a by gone era. I now fly CRJ 200/700/900s for US Airways.
I might have to get Joe to chime in on this board as he has much more vested interest in the mag conversion. I have only been present for the successful tests and have not witnessed any of the failures.
All-
The issue you are facing here isn't voodoo, it is simple mechanical design cross purposing. The entire reason you see what you call "nose diving" of the cartridge column when trying to use 54R cartridges in the ZB39 (8x56R) magazine is the issue of what is properly known as column drag. This, particularly with a prominently rimmed case like the 54R, is the problem of the total OUTWARD pressure exerted by the cartridge column as it is increased by stacking in the magazine box. This is most prominent with rimmed cases as the near total outward pressure is thus concentrated solely on the very thin rims themselves, against the inside sidewalls of the magazine box. Parallel sidewall, rimless, or rebated-rim cartridges might seem to have more contact area but this in practice is not generally so. The effect you are witnessing is that at some load value (# of 54R cartridges stuffed into the ZB39 mag), the total RIM DRAG of the 54R rims on the inside of the magazine box body causes the column to begin stalling out, and will eventually jam solid......the rims are dragging so much on the inside they cause the very tiny contact area to become a fulcrum point and the then heavier weight of the stack of the cartridges forward of that fulcrum point start to lower due to the free weight nature of the still moving forward mass of the column. THAT is your "nose diving".
The sole area of concern here, the "why" of this all lays in the magazine follower itself, namely and specifically, the SHAPE of the original 8x56R cartridge dummy shape on the top of the follower, and how that shape directly determines the internal outward stack force of the cartridge column against the inside walls of the box body. There is no issue loading the ZB39 mag full to its limit with the original 8x56R cartridges, because the follower dummy shape was properly designed to position cartridge #1 & #2 in the proper centerline-to-centerline relation, i.e., proper "height" of cartridge #2 over #1, and succeeding......as they stack up in the box body. That proper relation, IN COMBINATION with the angular measure of the radius of the box itself is what determines the internal frictional load of the cartridge column, as a total value. This is why follower dummy shapes differ with cartridge geometry and magazine capacities!
In order to use 54R successfully in the ZB39 magazine box body, you will need to relieve the much increased internal sidewall pressure, i.e., "DRAG", that stuffing 54R into it causes. And that issue is solely caused by the original 8x56R follower dummy shape positioning the 54R cartridges too far apart in the stack, cartridge centerline-to-centerline. To visualize this, you need to realize that a cartridge column that places the 54R cartridges closer together, though "higher", in relation to each other will reduce the internal frictional component as that column of cartridges tries to articulate through the ZB39 magazine box body in trail.
The way to affect this ("affect", with an 'a') is to modify the ZB39 8x56R follower dummy shape such that it will place cartridge #1 closer to the magazine centerline, versus just placing a 54R against the original shape. There is another issue at play too, in that the 8x56R follower dummy shape is angled to guide the 8x56R cartridges to the proper angular positioning inside the box body (proper for 8x56R), so that when the cartridge is stripped, the shoulder properly contacts the steering shoulder of the box body as it leaves the column stack and is thus properly positioned to enter the barrel chamber cleanly. You will need to modify, by milling, the original 56R dummy shape to position a 54R cartridge more toward the magazine box centerline, and slightly increase the "inward cant angle" of the 54R cartridges. Once the 54R cartridges can sit "closer and higher" in relation to each other, you will have (in general terms) reduced the internal drag sufficient to function properly. PROPERLY stacking 54R cartridges will reduce the available column height of the box body capacity to less than the original 25rds of 8x56R, though.
The ideal way to do this is mill OFF the original 8x56R dummy follower shape, then weld on a newly contoured replacement. Once can use a Lahti-Saloranta LS26 magazine follower as a donor shape, or as a guide. Or you can wing it and carve one out. Using plastic to first carve a shape and using tape to affix it to the milled flat ZB39 works to test the concept.
Restoring the internal cartridge sidewall drag to a level approximating that designed for the original 8x56R cartridges in a column will cause the ZB39 mag to feed 54R well. There is no need for any "helper spring" when the internal frictional values are restored, and thus no "nose diving" either.
-TomH
If we could all get our practical and theoretical heads together and do a few hours of brainstorming I think that a combination of both plus a bit of the bleedin' obvious would/could solve this problem quite easily. I wouldn't be starting with a blank sheet of paper but a few 'knowns' such as a) a gun that we KNOW will reliably shoot and function with 762x54R (yours'll do C-130!) and a magazine that we know will feed and function with a similar round. Yep, a standard and plentiful .303 Bren mag.
Together with a small workshop and................
Then start from there and deviate to 'unknowns' or variables if we need to. You game TacAdv? C-130? Joe? Brian?
Well Peter,
You have thrown down the gauntlet! I've got a modified ZB39 mag that works with 25 rds of 7.62x54r in semi-auto, maybe or maybe not in full auto. The ZB39 mags. were available in the US for $25, but no longer. They are now a hot item because of their use with Bren caliber conversions. The best outcome, as Peter mentioned, would be a conversion using a standard .303 Bren gun mag.
If Tom is correct it should be "a piece of cake". If not, it's a much more formidable challenge. C310, the ball is in your court. You have access to the 54R FA Bren and the ability to try Tom's relatively simple conversion. I've got a Lahti-Saloranta LS26 mag I'd be happy to send to you. BRP has very inexpensive Bren .303 followers.
Joe
And C-130 could whip over here in his plane and fly me over with a xxxxxxg big box of magazines............
Guys....remember too that I left certain things unmentioned, as they seemed obvious, but in the interest of shining light on all let me state that.....
-Many people don't realize that most times in designing a new gun like the Bren (nee ZB Vz26/30, etc.) the magazine is designed first, once the cartridge is decided, then the gun mechanism is built to accommodate THAT. Anything AFTER that first magazine design, matched to the original gun concept, is just many forms of modifications.
- The magazine follower shape and size is only the first element of the proper positioning of the cartridge column that the magazine body is designed to contain and control. Once the follower configuration is designed, the mag box body has to be matched to hold the cartridge stack at that relative spacing, so the box sidewalls are designed to THAT spacing, laterally.
- No matter how much work you modify the ZB39 follower to better suit the lateral spacing of the 54R cartridges, you're still stuck with the box body sidewall spacing in the ZB39 magazine design.....which probably is not ideal for the 54R cartridge. So, that issue is still to be reckoned with.....
- An LS-26 magazine can be used to judge the lateral spacing thusly determined for the unique 54R dimensions. That spacing, laterally stacking of the cartridges, is what you want to try and emulate as best as possible.
-TomH
All of this is very interesting. As my brain capacity is less than nothing right now, I had a 4:30am show today and a full day of flying, I will have to re-read this in tomorrow. My friend with the fa Bren has a CNC at his home. We like our toys, and can, and are willing to prototype. I have a 4:15 show tomorrow so I am off for some shut eye.
I had a thought while pondering the problems outlined here
just cut a slot in the side of the bren mag to allow the x54 rim out. then the x54 will bear on the case body inside the mag body. this will eliminate that outward pressure.start the cut above the mag well height on the mag.
just throwing it out there :madsmile:
I'd be starting with the tried and trusted old .303" magazines and go from there because they are another 'known' - in that they are an original FIT in your gun. The similarities between the .303 and 762R are just too great to ignore. But that is the starting point from someone who ain't tried it!
It's been a very interesting discussion. IMO I don't think the case geometry of the .303 Bren mag can ever be converted to a hi capacity 7.62x54R magazine but I'd sure like to see someone do it.
My experience, taking into account comments already posted in this Thread, with the 7.62x54R is summed up in my original comment quoted above.
Joe
Good technical discussion and I am inclined to agree with that sentiment Joe. BUT....... I always remember that old saying. 'Where there's a will, there's a way' But better still, the corrected version of one of my old bosses. Where there's a will, there's usually a simple way. On the other hand, one of my '.....more recent' bosses, MUCH higher in rank to me, changed all that to '.....where there's a will, I can usually make it a difficult way! And he usually did!
I'd like to think that the .303" magazine is the way to go BUT get rid of the platform guide and use an articulated/find-its-own-level platform.
.....being in the industry and having done a couple modern magazines, start to finish, and had them produced......let me throw out some numbers for you. There are at least four repop mags that have recently been done in S. Korea for the USA market....the M1 carbine mags (15 & 30rd), the M3 SMG mag, the STEn mag, and the old Mauser K98 trench mag.....these were all "copied", i.e., not built from original drawings so tolerances are hit and miss. These four were apparently done at rather low cost, less than $25,000 per design with minimum piece orders required. This represents the lowest cost to do a stamped steel magazine, when all you are doing is copying an existing article and in a very inexpensive labor and production market, i.e., Korea. These likely were all done on short-run aluminum dies, and the life expectancy of these dies is probably below 1,000 pieces.
For a customer three years ago, I did a reverse-engineer copy of the standard AKM stamped steel top-cover for a current production product here in the USA, the copied top-cover forms the base of a M1913 "Picatinny" style top cover optics mounting system- the 3 part progressive stamping die set cost $67,000 ALONE. Just the die set. Finalizing the dies to incorporate some additional late features cost another $11,000 to weld up and redo the first stage former.
I have done a 20rd 7.62x51mm M80 ball round magazine for the "AR-10" platform that used a four stage progression and cost right at $80,000. The last "big" mag I worked with was a close copy of the 10-rd Barrett M82/107 .50BMG M33 box magazine for a proprietary competitor of the Barrett that had been buying mags from Barrett but got cut off when he came out with a semi-auto .50BMG rifle that is now beating the Barrett in sales and performance. That mag job cost "only" $44,000 because the guy who needed it is in his own right a talented engineer and did most of the design permutations and CAD work on his own first, only taking it to the stamping house at the end.
Stamped steel is a wonderful application for mass production, but even in the digital engineering age, is still NOT cheap to play with to begin with. The only real way you can make money at it is by doing large scale production runs to offset the non-recurring up front costs.
Doing a modern "clone/copy" of the ZB29 mag is probably, at a MINIMUM, a $30K project to get to the first article stage and have a usable set of production tooling. So.....since this is only a hobby exercise, I am content with playing around with what we have to use as-is! ;-)
-TomH
I agree starting from scratch doesn't make sense. Joe H's design showed promise as it worked initially. Joe L. said the problems began to show up on the third or fourth load. The question is what is changing from a cold gun to a hot gun. The ZB follower also pinches the round towards each other. I would like to start with a new follower design and incorporate that into the zb mag. Machining new followers is a much less costly under taking esp being we have a CNC. I am not here to make money just feed the toys.
What is the width difference of the Lahti Saloranta LMG 20rnd 7.62x53R Magazine and the Bren? I would like to see the follower and do some tinkering. Curious how it compares to the width of the Zb26/30 8mm mags too.
Joe - I will have to pickup some Pittsburgh flights so I can give you a tour of the jet.
Are the SGM Tactical VEPR 7.26x54R 20 round magazines adaptable to the Bren?
VEPR 7.62x54R 20 Round Magazine
Attachment 58115 Vincent,
Hard to tell without having one in hand. They are made of Black Polymer and are advertised as double stack to single feed which is what the Lahti mag is. It is also designed to feed up, the opposite of the Bren.
Doesn't look promising to me but I've been wrong before:D
Joe
Derek,
The Lahti mag was designed to feed up. It is double stack and ends up as a single feed in the center of the mag. The Bren is double stack and grabs a round from either side. The main portion of the mag is much wider than the Bren well. The one I have will not fit the current Russian 7.62 x54r. It is not long enough. It was designed for a 7.62x 53R. The
rounds are for all practical purposes identical. It can be modified to fit the 7.62x54R by removing a curved plate in the mag. There is a very long Thread over on the Weapons Guild about adapting it to other rifles, nothing about the Bren. Just about everyone had very little luck.
I'll send you one. Feel free to experiment with it. I don't need it back.
Joe
I'm even more convinced that starting with a good 'known' before you start is the way to go. Tac Adv makes several valid points and has obviously been here beforee, especially with regards the slightly larger base rim diameter. By default, this will reduce the capacity by one mathematically but by doing so, this should make the curvature and platform configuration MORE adaptable. Especially since we might be getting rid of the now unnecessary (and friction causing) follower
Without the skill and learned depth of knowledge gained by C-130 pilot - and access to the parts I doubt whether your local gunsmith is the man! Why not have a chat over a beer with the man himself, Are you there C-130 pilot?
You can simplify the whole thing by leaving the butt slide, bipod legs and sleeve, gas blast plate etc etc as they are.
I have found that a vast majority of gunsmiths really have no clue. They simply have a license so they can own post sample machine guns. Most of the work is farmed out. I have photos and a step by step process all laid out. I can convert a Bren easily enough having done it. All it takes is time as the learning curve is over! You definitely need a mill, and if you want the mag reinforcements a lathe. The parts Peter discussed are all 'frosting' as I like to call it. Bolt on type items except for the gas shield which is easily fabricated. I would be more than happy to discuss.
Joe L and I have some ideas as far as the mag and we are going to put together a couple of frankenmags for giggles to see if we are heading down the right path. Apex gun parts here in the US had Bren mags for $2.00 ea. Cheap for parts, springs followers, and cutting and brazing on a Lahti upper. It will be an interesting concept test to say the least.
What seems to be the problem with 7.62mm magazines for the 7.62mm L4 Bren conversion. If you haven't got the 30 rounders, then the standard rifle magazines fit and function - as they were made to interchange. And even if you can't get the UK 'big lug' type, the FN type will fit. And if they are a bit loose fore-and-aft, then it's simplicity itself to fabricate the big lug.
Or am I missing something in my old age?
I've got plenty of 30 rd L4 mags if in need. Both new and used.
The thread kind of got derailed. I have 14 7.62 mags for my L4. The mag conversion is for the 303 guns to shoot 54r. 54r is .18 per round. 7.62 is close to .60 and .303 is usually even more. cheaper than dirt recently had a bunch of hxp for .44 per round to my door. It's all about economy.
C310pilot,
I finally received my Sarco L4A3 parts kit. Kit was pretty greasy and came with no barrel and the receiver was torched in 3 locations which I am pretty sure will cause it to be unrebuildable unless I use other cut up sections from other cut Bren receivers.
I am pretty much immobile since I just had knee replacement surgery on 1 December.
I have some Bren Mk1 cut receiver pieces that I think could be used to rebuild the original L4A3 receiver (have access to those pieces) but worse case scenario I still have two Interordnance 3 cut Mk2 Bren receivers that I could use. Unfortunately, these kits are buried in my parts stash and I can't access them right now.
Do you have a manufacturing license to rebuild these receivers or do you have some kind of build manual that you would sell so I can get this Bren built. I still have to wait for Sarco to produce those L4A3 barrels sometime later next year.
raexcct2,
Can't speak for C310 but I came to the same conclusion you did about the L4A3 kits. At a minimum you will need a front section from a MGS Mk II kit. From the pictures It seems everything forward of the mag well is scrap. If you check out the link below there are pics of worse cuts than shown in Sarco's ad. I thought about using IO Mk II kit, rebuilding to semi then machining the mag well area for the FAL mag. But then you are really paying $600 for the ejector block and a few barrel fittings and still don't have the barrel.
Good luck with your knee replacement I've had two. I feel your pain:D
As far as "How to" The link below is where it is at:
Login
Got Deal & Steals regarding L4a3 kits and Bren builds for rebuilding to semi info.
Joe
Bingo!! It's a sad state of affairs but the now-active import destruction regs pretty much have killed off the idea of re-buildable parts kits for almost everything.
The "good news" is that all of the earlier imported kits are all out there still.......and I'd venture to say that probably 95% of those who bought one never end up trying to build it.
-TomH
Joe,
Thanks for the post on the Sarco L4 parts kits. I was considering selling my Mk II kit to buy an L4 kit as that's what my end-goal is - after seeing those photos, I think I'll stick with what I have and wait for the barrels to become available!
I understand that 7.62mm barrels are being formulated as we speak. They're probably already being made.........
That's one less headache to deal with. I was never able to locate an L4 barrel in the states and while I did get a response from the Lithgow museum (stating they couldn't sell copies of engineering drawings) my inquiries to the Canadian War Museum and Nottingham all went unanswered.
On a somewhat related note, in your professional opinion, how difficult is modifying a .303 breechblock to 7.62x51mm?
Breech blocks....... Supposedly, a .303 breech block is said to work by simply fitting a 7.62mm extractor!
Yep! As stated here several times lately, a std .303 bolt will work just fine after you install a std 8mm/7.62NATO extractor. If you don't care about historical replication of the L4 mechanically, you can be up and running shooting .308 perfectly with three drop in parts:
-7.62 extractor (installed in a std .303 bolt)
-South African/DENEL 7.62 NATO BBL
-Bulgarian ZB39 mags ( filled to the 25rd capacity)
I must point out though, that this recipe is based upon you being able to source all three of those parts......which is not always easy anymore......and then, that this is based upon their installation into a factory original (uncut) machine gun receiver. Any variation upon that originality, such as a welded receiver and/or re-built to semiautomatic-only function......may impair the "plug-and-play" compatibility of the above parts. It will undoubtedly be able to make it all work, but custom fitting of the various interfaces will likely be required.
It does work flawlessly in an original factory gun. Not an "L4", but that isn't the goal with this recipe.
-TomH
My goal is an L4 clone for my reenacting unit.
I've got a small stockpile of L4 magazines, so that's not an issue. And as long as Sarco produces more barrels than they have kits, that problem is sorted as well. Which just leaves the breechblock. And I don't care if the gun is 100% authentic on the inside!
Attachment 69117Attachment 69118Attachment 69119
I have a Historic Arms L4 clone. It has the L4 mag. I had to change the butt stock, carrying handle and bipod to the correct ones. It has the South African barrel so the flash eliminator is not correct, but other than that it looks good.
The bipod sleeve (the part the rotates on the gas cylinder) is wrong too. You could re-profile the mid section of the barrel to suit if you were so inclined. An L4 type flash eliminator should be easy to obtain and fit. Then you'll have an externally almost perfect L4
Is the bipod sleeve not the standard mark1 fitting? This is how I bought the bipod. I have a mark2 bipod too. Should it be a hibrid of the two?
Hopefully KevG will put up a photo! But basically, the L4 bipod sleeve has a steel shroud that extends rearwards over the gas cylinder vents. Simply to shield the brighter flash that comes from the 7.62mm blast venting from the gas cyl.
Off the subject - sort of for a minute....... This was a bit troublesome on the Navy L4A3 and 5 guns because the ferocious blast was directed rearwards onto the blast plate which was a separate part on the ex Mk2/A3 and 5 guns. The blast plate was meant to be fixed solidly to the gun body (through the medium a tapered cross-pin) but the blast could cause it to work loose. The inspection standard was relaxed by the NOD so that slight looseness was acceptable providing that......... And off it went on and on and on.
Now where is KevG with the photo.......?
Sleeve machined round and tubular shroud brazed all round. The L4 type bipod sleeve was approved for fitting on all Bren guns after May 74 subject to a WSE notice being issued....... Don't worry about the technicalities!
.......stolen pictures, for discussion.
-TomH
That's the one. Thanks Tom. You can see that the factory conversion to L4 didn't waste anything! The actual sleeve was turned down to accept the shroud part. Even the old .303" barrels were stripped of the gas blocks and re-used on 7.62mm barrels. You can occasionally see the former makers mark or logo. The foresight blocks were also utilised on the new fluted flash eliminators. Backsight leaves were also ground down .014" and new 7.62mm markings were engraved (or were they rolled?)
Depending on the size of the buying nation chequebook, the Mk2 butt slides were slimmed down and contoured to Mk3 spec too.
There was a drawback to the shrouded L4 type bipod sleeve. It simply wasn't as robust or tough as the old sleeve (Pic 3, top left). The sling loop part was machined off during the conversion but it was THIS loop that prevented the gun tipping over onto its left side. On the L4, all that prevented the gun tipping was the flimsy shroud that interfered with the barrel. A few bashes against the barrel and the shroud would collapse......., followed by the gun!
Pic 1 shows what I mean about the bipod sleeve shroud. It directed the ferocious blast of spent gas onto the blast plate - that's the plate, just behind the shroud. The plate is sandwiched between the gas cylinder that's retained by the visible taper pin and the body. Originally the blast shield should be TIGHT but the relaxed NOD directive later stated that a slight amount of movement (which is never defined of course!) was permissible but the actual GAS cylinder must remain tight.
I was told by one of the RSAF 'Lockies' that the conversion also entailed the use of threaded Mk3 type gas cylinders. This is incorrect and not possible.
Interesting thread
Guys,
I'm trying to get straight what goes with what. I have never handled a 7.92 or L4 Bren.
I know:
.303 British Barrel with .303 British breech block
SA .308 barrel with .303 British breech block (L-4 Extractor)
.303 British Barrel (re-bored & re-chambered to 7.92(8mm Mauser))with .303 British breech block (L-4 Extractor)
What I'm not sure of???
7.92 (8mm Mauser) Barrel with 7.92 Breech Block (not the same as the .303??)
7.62 Nato L4 Barrel with 7.62 Nato Breech Block (Same breech block as 7.92????)
I believe I read somewhere that the 7.92 breech bolts were used in the L-4 conversions. Also the 7.92 breech blocks / 7.92 barrels were made different from the .303 so that a .303 couldn't be inadvertently chambered in the 7.92.
Thanks for your comments,
Joe
Joe, Yes, you are correct in your combinations above.
The reason for having to match (original Inglis) 8mm barrel + bolt, and L4 barrel + bolt is that those particular bolts are physically dimensioned differently than a std .303 bolt, for just the reason you stated.
This is the epiphany that the guys at DENEL had.....if you simply made the barrel shank of a new-made .308 barrel LONGER (by the length of the cartridge feed horns on the bolt), you could then keep the std .303 bolt and not have to make new ones specific to the caliber change. Apparently, they regarded the off chance of someone trying to use the wrong ammo a worthwhile gamble in light of NOT having to make another new (and expensive) part at the time (of international embargo). With just the "longer" .308 barrel, they got the functionality desired.
Yes, you are also correct, original Inglis 8mm bolts were used at first (type proofing), and later new-made "L4" bolts are fully interchangeable to my knowledge. And too, both original Inglis 8mm extractors and all other "7.62mm" extractors, no matter where made, are functionally interchangeable to my knowledge.
Warren W. may have a salient commentary on the Inglis angle.......and Peter may have to add anything I missed....
-TomH
All I can add is that some of our 7.62mm L4 breech blocks were marked 7.92 as were some of the extractors. The Trial;s team Warrant Officer, WO1 Fogwell died a couple of years ago. I wish I'd spoken to him at greater length. He was scathing about the A1 gun magazines, the HOD and the lack of magazine lip support (the body inserts) but all that was soon corrected. He called the L4A4 '.....the Bren gun at its finest'
I can't say that reprofiling YOUR barrel will be safe as I don't know what ammo loadings you'll be using of course. But the profile of our L4 A2 onwards barrels were perfectly safe. (The L4A1 gun barrel was slightly thinner at the breech end.) Will give diameters tomorrow.
Here they are, diameters for the later L4 barrels.
Rear section, recessed section from breech area up to the cocking handle sleeve 1.150" dia approx
Centre section, from the carrying handle sleeve to - either side of the location section - on to gas block .915" approx
End section from gas block to flash eliminator .870 approx...., (same as all barrels except Mk1 type)
Bren barrels are an absolute pleasure to machine providing that you've got a sharp tool of course - if you'll excuse the phrase........ Medium speed and the biggest roughing cuts you can worked best for me converting some. Followed by the radius parts and finishing cut.
Hello all, I have an L4A4 deac old spec that I'm thinking of selling any idea what it is worth?
I think you should check out the new ( as of the 8th of April) EU rules on deactivation regarding the "Placing on the market" of UK Deacs. Many people could potentially be caught out by this little publicly publicised law.
The quicker we tactically withdraw from that shower the better IMHO and that applies to alot that we pay £58 million pounds a day for, changing our way of life...............Never..Sacre Bleu, who do they think they are:banghead:
It's ONLY statute law that counts. No law, no offence don't forget