My .308/7.62mm fullauto conversion- Plug & Play Success!!

Finally got around to looking at doing a .308 conversion for my '42 Daimler Mk II fullauto gun.

I've been picking up the various bits over the last year, finally got interested enough to put it all together,,,,litterally as it turns out. ;-))

I've been reading with much interest the various posts of doing the .308 conversions.....with all the ups and downs, so I now feel kind of sheepish to report to you all that, for my original gun at least, this turned out to be a "plug & play" exercise........not sure what to feel about that bit of luck but I'll report on my affair here.....

My receiver/gun as I said, and have posted several pictures around other posts herein, is a factory original condition Daimler Mk II from 1942, so that may/may not have turned out to be an important data point in this....

I am using one of the long-ago imported "South African"/DENEL/Lyttleton Eng. 7.62mm barrels that were new made for the SADF conversions there. Many of you seemingly have the same barrels.

I had been holding off on this project because, stupid me, I never really looked at the damn barrel carefully when it came in except to note the R1/FAL flash hider they used, which I think is a nice visual change for the BREn. Then one of you pointed out here that these barrels are markedly differently constructed in the that the barrel shank end is cut back, and chambered accordingly, to permit use of the standard .303 bolt with horns. I had been thinking I'd need to machine the barrel base for the normal .303 bolt, machine in the ramp to accommodate the feed horns a la the .303 barrels. That was a major discovery.... ;-))

In this particular combination of receiver & S.A. 7.62mm barrel, I was very lucky I think in that the combination breached up tight on the first try, and the bolt locked perfectly, with both the currently installed barrel lock and bolt locking shoulder. With that bit of luck, I checked the head-spacing and was in luck again. I swapped in a S.A. 7.62mm extractor into the normal .303 bolt it had in there, and that was it.

I am using unmodified Bulgy ZB-39 mags. I have read a lot here about using them for various things but wanted to try them first as-is. They took the full 25rds no problems. I was also lucky in that they locked in perfectly with the Mk II mag catch I had installed......

I decided to try some Russian "Brown Bear" steel case .308 I have lots of. See pictures below. The whole thing went together Plug & Play style.......I fired 160rds in various semi-auto and fullauto shooting, with only a couple of things to note.

As JoeH here pointed out, occasionally, I had the last round fail to get picked up out of the magazine. It was an intermittent thing, maybe 20% of the time. Interestingly, when that happened, leaving that single round in there, the gun would fire it if cocked again.

No failure to chamber or fire at any time, other than as above for the last round. I tried both gas port position #1 & #2. Both ran it fine, though #2 seemed, with this .308, to run more smoothly and I am guessing at about 600RPM or so.......I'll think about as I shoot it further. So far, so good.

Here are some pictures; I'll get live fire video next time out.
-TomH

Attachment 63376Attachment 63377Attachment 63378Attachment 63374Attachment 63375Attachment 63373

We did one once using an 8mm Inglis. All we did was changed barrel(plus the minor fitting), checked headspace and carried on. Shot like yours does...used the same mag and bolt too...

Tom,

I'm green with envy. FA Bren in the US.:D

Joe

[QUOTE=browningautorifle;334679]We did one once using an 8mm Inglis. All we did was changed barrel(plus the minor fitting), checked headspace and carried on. Shot like yours does...used the same mag and bolt too...[/QUOTE]

I assume you mean "...used the 8mm Mauser magazine and bolt too..." ?

Quote:

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Originally Posted by browningautorifle

used the same mag and bolt too...

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Like I said, used the same mag and bolt too...the ones in the gun. And, they worked fine.

Must have had an extractor change surely! I have just used a .303 BB assembly in an L4 gun (not the same I agree....) with a slightly dinged/distorted drill round (to replicate it having been fired and tight in the chamber) and the 7.62 drill round just moves to the rear a couple of mm's, then upwards slightly and slips off the extractor. It's not exactly comparing like with like but the mechanics of it are the same.

The trouble with a converted gun WITHOUT the magazine well stop inserts is that before long the gun feed lips will tear away. Or maybe this only occurs with those guns that use L1A1/FN type magazines that sit slightly deeper in order for the BB feed horns to make better contact with the smaller base rim diameter of the 7.62 cartridge

Quote:

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Originally Posted by Peter Laidler

Must have had an extractor change surely!

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It was an 8mm gun boys, the 8mm extractor...and little square mag...he didn't have any 7.62 extractors so I know we didn't change it.

The 8mm Inglis Bren talk has thrown a kink into the conversation, can TactAdv show up a picture of the chamber end of his SA barrel?

There have been 3 different recent conversations which seem to have confused the waters:

- The L4 7.62mm series used 8mm Inglis Bren bolts & headspacing locking shoulders, so an L4 Bren barrel should lock into and headspace in a 8mm Inglis Bren assuming the use of the ZB26/30 8mm magazine.

- The "Government" SA 7.62 conversion used a modified .303 bolt (reducing ring silver soldered onto the face of the breech bolt) with a 7.62 extractor. the .303 bolt allowed them to continue the use of .303 locking shoulders. The barrels chamber end is contoured as a .303 barrel (if I understand correctly) to allow the use of the .303 bolt. The magazine well is altered to accept metric FN mags, and an ejector block fitted with a hold open was fitted.

- .303 barrels have been bored out and rechambered to 8mm Mauser, these barrels use un-modified .303 bolts which are fitted with 8mm Mauser extractors, newer condition Brens require some opening up of the rear of the magazine recess to accept 8mm ZB26/30 type magazines. This type of conversion "may have been" originally done at the behest of an unknown government user.

- current civilian owners of working Brens have mixed barrels, bolts and magazines in order to obtain guns which function in a variety of calibers (8mm Mauser, 7.62x54r, 8x56r(Austrian/Bulgarian/Hungarian), 7.62NATO, .303 British) which are available to owners...

---------- Post added at 08:32 AM ---------- Previous post was at 08:26 AM ----------

Quote:

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Originally Posted by browningautorifle

It was an 8mm gun boys, the 8mm extractor...and little square mag...he didn't have any 7.62 extractors so I know we didn't change it.

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As far as I can tell, the 8mm extractor is the same as the 7.62 extractor....certainly much closer certainly than a .303 extractor..

You're all correct about the 7.92mm BB's and extractors and L/Sh's. These can be - and were - used un-altered in UK L4 guns. We know this because the EMERs stated it quite definately, the early parts lists identified them by their different drawing numbers and occasionally you'll see the 7.92 punched into them occasionally.

I understand that a very similar extractor, marked with a small letter T (for TANK) is also useable in a 762 or 792 gun as these extractors were for use in the 7.92mm BESA gun. But as I never had anything to do with BESA guns I can't confirm it. The last BESA's went in 1966/67 or so with the last Churchill tanks

How much do the brens cost as when I win my lotto millions I intend to move the whole lot of us over to the USA and buy a nice flat land with no neighbourghs and set up a a super longrange where the 416/478/ma duece could play as well bring in some brens/stens top it off with 6 sniper T's and get some ammo say 15oooo should do the trick

Okay, posting some quick crappy pictures here...Peter asked to see the breech end of the S.A. BBL....

Things to note- the magic of these S.A./Lyttleton BBLs is that the SHANK is about .090" shorter than a std .303 BBL shank, which then allows the std unmodified .303 bolt face still with feed horns protruding forward to fit against, i.e, lock against the std .303 locking shoulder, i.e., since the shank is shorter by the same distance as the length of the fee horns, it doesn't interfere. Note that these pictures clearly show the ONLY cut/relief on the breech face is for the EXTRACTOR claw......no cut for the bolt feed horns to drop into!

It's a brilliantly simple solution, though it would seem that in so doing you'd have a lot of unsupported cartridge case extending, it doesn't seem to matter one wit, in actual firing. None of the .308 fired cases exhibit any bulging at the case head area......so all's good. A brilliantly stupid solution that works....

I'm probably going to go shoot it more tomorrow again, so I will get some video of it shooting in .308 with all these conversion parts installed.

Again, the total conversion consists of:
-S.A. 7,62x51MM NATO caliber barrel (Lyttleton proprietary design)
-S.A. 7,62mm extractor (suspect identical to all other 7,92mm/7,62mm extractors)
-using unmodified Bulgarian Zb-39 25rd magazines.

Comments.....????
-TomH

You said it all Tom ..........so all's good. A brilliantly stupid solution that works....

But as I have said many times, in a calibre conversion, the shooting is simple. In a machine gun it's perfecting the remainder of the cycle at 10 times per second that is the problem. Cock, feed, load, lock FIRE. Unlock, extract, eject PLUS the events that take place within those primary features and simultaneously to them. But it works......

I would like to do the same to my MkII and use the much easier to find 308 ammo .

tr,

Here is what you need:

Barrel Assembly, .308 (7.62mm) L4 w/Flashhider, Used Factory | Gun Parts

Search

Zb-39 25 Round Magazine | Allegheny Arsenal

be sure to check headspace for the .308.

Discussion here:

Login


Joe

Quote:

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Originally Posted by Joe H

tr,

Here is what you need:

Barrel Assembly, .308 (7.62mm) L4 w/Flashhider, Used Factory | Gun Parts

Search

Zb-39 25 Round Magazine | Allegheny Arsenal

be sure to check headspace for the .308.

Discussion here:

Login


Joe

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Joe what extractor will it needed , will a .7.62 x51 mm from a L4 that BRP has for sale be correct ?

tr,

The extractor from a Bren L4 7.62 Nato kit or a 8mm Mauser Bren will work, they are the same extractor.

The .303 British extractor will also work with the ZB39 8mm Mannlicher (8x56R) and the 7.62 x 54R Russian conversion.

The "L4" type extractor will work with the 7.62 Nato (.308 Win. ) and the 8mm Mauser (8x57)

Joe

TactAdv,

Conratulations on a well running piece of kit. My question is along the questioning by PL. Happy the gun is functioning, but is everything really working in a proper interface? Don't want to rain on anybody's party, but will you be doing any harm to your rather expensive heirloom? It may take thousands of rounds, but I would keep careful watch over certain aspects to be sure you were not developing any long term damage.

Beyond that, this discussion has now lead ME down the primrose path, so I ordered up the barrel from Numrich, which is quite expensive, but not as expensive as owning a P-51. lol.

I have a Mk III or a MkI (semi) I will test headspace on and see how it fits. Just need the extractor and I believe I have a spare for the L4, so should be good there. I am confused as to model number of the magazines though. I THOUGHT I had ZB-39 mags, but when looking at the link, the mags recommended look just like .303 mags? Here is what I have. I had understood these were for the Hungarian 8x56r. Is that not correct?

The dark blued magazine fits in the Mk III just fine, but because of the shorter forward locking tab, it can be tipped forward and bypass the mag release with ease. I doubt it would stay in place under firing conditions? I may have to work on a solution for the shorter forward tab on these mags, if they are even appropriate for the .308 conversion? They aren't doing me much good in 8x56r Hungarian. Not unless I come across a massive supply of cheap Hungarian. (have a barrel too, but have never tried fitting it to either of my Brens.

Quote:

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Originally Posted by Peter Laidler

Must have had an extractor change surely! I have just used a .303 BB assembly in an L4 gun (not the same I agree....) with a slightly dinged/distorted drill round (to replicate it having been fired and tight in the chamber) and the 7.62 drill round just moves to the rear a couple of mm's, then upwards slightly and slips off the extractor. It's not exactly comparing like with like but the mechanics of it are the same.

"The trouble with a converted gun WITHOUT the magazine well stop inserts is that before long the gun feed lips will tear away. Or maybe this only occurs with those guns that use L1A1/FN type magazines that sit slightly deeper in order for the BB feed horns to make better contact with the smaller base rim diameter of the 7.62 cartridge

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"


I am understanding just a little more each time comments are made... As I slowly become aware of the nuances of the Bren, I can see that the L4 mag did need to be seated deeper, as you say Peter, because of the smaller rim face. Then along came the gouged magazine follower, causing the feed horns to be abbreviated as well. One begets the other, begets the other. Kinda Biblical. lol.

Not having spent much time researching South African conversions, what did they do for mags? Was it the FAL Metric style? And at some point, what was modified about the mag well to allow the FAL mags to fit and lock?

In these mentioned conversions, a non-7.62 mag is being utilized, but that is ok for range work. I know the SA Military Brens must have had a more thorough solution.

AER,

I had a similar fitting problem with the Semi Bren & the ZB39 Mag. My MKI which was made from an IO kit and has a spec mag well and worked with an unmodified ZB39 mag. Locked in perfectly.

My MkII was made from a MGS kit and had a "loose" mag well. Worked with a .303 mag but the ZB39 could slip out as you experienced with your semi Bren.

My fix is pictured below. A shim soft soldered int between the ribs of the lower rear of the mag.

I also found that removing the follower guide (pictured) from the mag allowed more rds. in the ZB39 mag.

Here is some info. I found about the SA Conversion:

www.nutria.co.za - View topic - South African Bren gun

Joe

Thank you Joe, will read and digest.

Oh to locate a coveted Mag release, ejector conversion unit...

Do any drawings exist?

The obvious question, does the front of a .303 mag well accommodate the small triangle lock tab on the FAL mag? I sure it locates, but is that small bit of meatl enough to keep that mag in place securely?

Form that article Joe, it does sound like the SA conversion was somewhat suspect and relegated to other duties besides front line. Good read though. Thank you.

I may try brazing a small piece of metal to the fronts of the ZB mags. Try one at least. See if that is enough to have a more positive lock.

Quote:

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Originally Posted by AmEngRifles

Oh to locate a coveted Mag release, ejector conversion unit...

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L4 Bren Ejector Block, 7.62X51, *Good* - Bren - Light Machine Guns - Machine Guns

Watch what you wish for. Any conversion for the FAL mag entailed a lot of work. In addition to the receiver machining for the mag and ejector block, the mag stops in the the receiver were almost completely removed. The Enfield conversions added plugs to reinforce the mag stops.

When you were done you only can use 7.62 Nato. With the conversion under discussion you can switch back and forth between .303 and 7.62 easily.

Try different thickness shims in the rear of the ZB39 mag. per the pic. Just slip them in until you get the right fit then soft soldering will work and won't screw up the mag.

Joe

Joe what should I head space gauge the S.A. barrel in 308/7.62mm at go min. , field, and No go ?

Just a wee note tacked on to this thread.

Did a caliber swap on my Semi-Auto MkII at the range today
Took less than one minute to change over from .303 to 7.62x51 with the South African barrel. Very pleased with the results and amazed a few of the Yanks at the range while doing it. Next time I’m going to bring my 54R conversion as well...🤣🤣

One thing I did was to remove the follower block/aux spring from my ZB-39 mags to better accommodate the 7.62 round. I did find out, like the OP that the last round will not feed due to the base of the round being below the bolt hold open on the magazine. I’m thinking of trimming this off to eliminate this from happening.

Cheers all

Gary

Gary, Thanks for the information.

I keep wondering, "who cares if there is one round left in the mag?"...

It is the "follower's helper" so to speak.

Joe H, What I am trying to figure out is what sort of mag well conversion did South Africa use to fit L1A1 or FAL mags into the Bren well? They seemed to obviously not have gone the route that the UK did in having the mag stops riveted into place, but they must have milled away some portion of the interior .303 feed lips?? I am looking at the mag location trying to determine if the mag is forward, with a new mag catch/ejector assembly in place to take up excess room at the rear of the mag well, or some form of mag well filler in the front, to push the mag back against an existing .303 mag catch/ejector assembly?

As you mention the modifications required, I won't attempt to modify my .303's in a permanent fashion at this point to take the L4 mags. I have a finicky L4 for that (still trying to work out my BOB issues) but it will be nice, if even just temporarily, to allow me to shot 7.62 out of a MkIII or otherwise. Kind of a parlor trick.

If I can attach some specific pictures from the link I will...

Quote:

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Originally Posted by csmarcher

...snip...
One thing I did was to remove the follower block/aux spring from my ZB-39 mags to better accommodate the 7.62 round. I did find out, like the OP that the last round will not feed due to the base of the round being below the bolt hold open on the magazine. I’m thinking of trimming this off to eliminate this from happening.
...snip...

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I would live with the un-fed round unless it becomes a safety issue - removal of the mag follower hold open feature will (eventually) lead to increased wear to the receiver bolt stops.

Quote:

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Originally Posted by AmEngRifles

Joe H, What I am trying to figure out is what sort of mag well conversion did South Africa use to fit L1A1 or FAL mags into the Bren well? They seemed to obviously not have gone the route that the UK did in having the mag stops riveted into place, but they must have milled away some portion of the interior .303 feed lips?? I am looking at the mag location trying to determine if the mag is forward, with a new mag catch/ejector assembly in place to take up excess room at the rear of the mag well, or some form of mag well filler in the front, to push the mag back against an existing .303 mag catch/ejector assembly?

...snip...

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South Africa only used FN-FAL (small front tab) magazines.

"KevG" had posted pics of a SA 7.62 Bren some years ago. IIRC his comments were to the effect that the SA ejector block was clearly based on that of the X10/L4A1, however it is not interchangeable.
http://weaponsonline.proboards.com/thread/993

Deceased former member "John R." was in Rhodesia in the early 1970s and had written a description (must have been on another board) of the trials and tribulations of fitting the brand new SA 7.62mm Brens to actually function reliably.

I remember him commenting that the feed rails were so sharp that more than once he cut his fingers on them.

in the photos that you posted you can see the button used for the bolt hold open (similar to the X10 and L4A1).

Thank you LE. Thank you for the updates as I have missed many of the earlier contributors comments and express my gratitude and respect for those members not with us any more. I will do some more searching on archived content. I am unfamiliar with the "hold open" feature, but know exactly what button you are talking about as it was pretty prominent in the #2 picture I repost of the two Brens together. I also see they did use the Metric spec mag, not Inch mags. Thank you.

Good stuff in that KevG link. It is obvious that S.A. also went through fitment issues with Metric mags in order to have them feed correctly. The link talks of filling along the feed lip rails inside the mag well, then re-contouring to work with the FAL mag. I definitely don't want to mill a small triangle receptacle, so the front lug will capture, at the front of the mag well. As they point out, you quickly end up in the mag cover retention spring well.

I suspect I just won't go down that road and use the ZB-39 mag for some form of satisfaction, unless the barrel just won't headspace up. Fun times ahead. At that point, I would rather mess up some ZB-39 mags with internal alterations or larger retainer tabs if they appear to feed decently. The .303 platform is certainly all ready to accept the mags, and hopefully I will find that feeding from the mag is not an issue, other than normalizing repeatability to the mag/gun interface.

Observation/question. The S.A. mag button looks like a different design than any of the UK models, is that correct?

Found this picture attached to a thread of 2010 date. Helps explain how they went about it.

Here’s a dumb question. IF the South African 7.62 barrels work as they do in .303 Brens, then will L4 barrels do the same thing?

Jumped on the S.A. 7.62 barrel so fast, then started thinking, “ you own two L4 barrels”....

Doh!

The barrel shank chamber end , maybe longer ? Will the .303 bolt with horns need to be reworked ?

Quote:

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Originally Posted by AmEngRifles

Here’s a dumb question. IF the South African 7.62 barrels work as they do in .303 Brens, then will L4 barrels do the same thing?

Jumped on the S.A. 7.62 barrel so fast, then started thinking, “ you own two L4 barrels”....

Doh!

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8mm and L4 Brens use other head spacing shoulders.

Don’t see why it would be longer? Shorter, yes. But point taken. I will measure and compare. The 7.62 does not have feed horns like the .303, so I suspect (but do not KNOW) that they will clear. I got some comparing to do. I need a set of 7.62 Go-No go gauges.

Quote:

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Originally Posted by AmEngRifles

Don’t see why it would be longer? Shorter, yes. But point taken. I will measure and compare. The 7.62 does not have feed horns like the .303, so I suspect (but do not KNOW) that they will clear. I got some comparing to do. I need a set of 7.62 Go-No go gauges.

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Any updates on the barrel you ordered , what type of front sight does it have ,is it a standard .303 blade or is it a Uzi type ? Did it headspace with out problem ?

Hey tr63, got the barrel but have been so busy, only dealt with it in a cursory fashion. I tried it n both a .303 and the L4. Don’t recall which one, but it locked up pretty tight in one rifle, meaning I had to use quite a bit of downward force for the latch to lock closed. These barrels have been refinished, so the parkerizing could be a little thick on them. Locked in fairly easy in the other...I think it may have the Uzi front sight, but do not recall without pulling it and looking at it again. It does have quite a few pitted areas, which have been covered by the parkerizing. Hopefully they did something to stop the rust or remove it before the park job? The bore is very nice. No pitts, no corrosion. All in all, looks more like a $500 barrel instead of a $600. If there were no putts or minimal, then $600 would have been appropriate.

As of right now, I have no 7.62 chamber gauges. Since I don’t usually “ build” rifles, it has not been a high priority on my list. As soon as I get some time to focus on it, I will turn my attention back to the conversion with this SA 7.62 barrel.

I still need to get with csmarcher ( came out “cam archer” first typing. I like that ID!) to work on my L4 which has given me fits. I don’t think I would ever recommend anyone BUY one of these rifles without getting to see it operate thru at least 3 mags of 28 rounds each. Building your own is another consideration. Saves you loads of money.

My South African 308 barrel arrived from GunPartsCoro by way of FedEx today . Along with a 7.62 extractor . The barrel came with a new gas regulator installed and the African black plastic carrier handle . It slid into my Bren Mk II and locked in properly with the existing barrel nut . It head spaced on the 7.62x51 Forster go gauge 1.630 and the bolt would not close on the no go or the field gauges . The front sight is the standard British blade type not the Uzi type . It has a very nice dark black Parkerization with no pitting . I paid $539.00 with my discount the normal price was $599.00 with free shipping .

Sounds like you got a nice package. I should have contacted GunParts and requested a replacement. They may still have a few?

Quote:

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Originally Posted by AmEngRifles

Sounds like you got a nice package. I should have contacted GunParts and requested a replacement. They may still have a few?

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When I placed my order for the barrel I asked if they could hand select for the best condition with least amount of pitting . The standard reply was that they do not offer that service. They pick the item off of the of top pile or from the top of bin and as the sales person on the phone said " you get the luck of the draw ". I noticed that my CZ-39 mags. will need the front tab added on to make a tighter fit in the mag. well . It head spaced with the min. 1.630 go gauge and the bolt will not close on a 1.634 no go gauge , I wonder ,is that too tight for a Bren Gun ? Maybe Joe H can jump in on the head space ? I have a C/R license and they gave me a dealer's discount that is why the barrel was $539.00 not $599.00 .

tr,

Glad to see you are using the .308 Win. specs. Since the bolt will close on the go gage (1.630") and not close on the 1.634" the Bren should have adequate operating clearance. The min. space between the bolt and the locking shoulder should be not less than .002" for operating clearance.

Below find the Headspace section of the "Bren Manual". Note that the gages are for .303 British.


Joe

Thanks ,Joe for coming back with the head space information . I noticed that when I had the bolt fitted with the .303 extractor it will extract the .308 cases when I hand cycle the action ,is that normal ? I Had removed the extractor and the ejector when using the head space gauges . The barrel came with a gas regulator installed . Did the South Africans use the original .303 regulator with out modifications ?

Quote:

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Originally Posted by tr63

I noticed that when I had the bolt fitted with the .303 extractor it will extract the .308 cases when I hand cycle the action ,is that normal ? I Had removed the extractor and the ejector when using the head space gauges . The barrel came with a gas regulator installed . Did the South Africans use the original .303 regulator with out modifications ?

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I noticed the same thing about the extractor. It appears to work hand cycling but is apparently unreliable in actual firing. There has a previous discussion about this quite a while ago.

Don't know if the regulator is the same as the .303. its easy enough to check. The big variable is the additional spring for the semi operation and how accurately you receiver has been welded. Only one way to find out.

Joe

OK, had a little time today to spend with my Bren. Specifically, my South African .308 barrel and my Bren.

The barrel has the black synthetic ( thought it was just a painted wooden handle originally) handle, with the MkI profile, meaning it has the nice swell, not the tube type, like the late model Bren handles. It also has the standard style Bren front sight. Don’t ask me WHY I thought I may have an Uzi style front sight!? Guess because I pulled my Uzi out a short time before responding to the inquiry. My mind sure can mix up facts. Anyway, going to just keep this barrel and be happy. The bore is very nice and that is what counts. Mostly.

I tried it on the Mk III, PG. locked down easily. Bolt slid home nicely, on a live cartridge. Had a very small amount of play. Probably any is too much? No gauges at this time. Soon.

Tried on the HA MkI. Lever did NOT lock down with hand pressure. The locking portion of the lever, which grabs the underside of the receiver so it stays put, was about 1/8” or less away from locking. Could have taken a rubber mallet to it, but I figured I would NEVER get it unlocked if I did that. Might should try the MkIII locking lever in the MkI when using the SA barrel. Haven’t tried that yet.

Same with the HA L4. The SA barrel lock nut gets very close to locking down,, but I’d about 1/16” away from doing so. Again, refrained from taking a mallet to lock the lever, knowing the pry forces to get it back open would probably lead to a minimum of scratching of the receiver. Just let it be. Will try to secure a few alternative locking piece. I believe BRP carries an assortment. Will try the MkIII lever first since the barrel goes right in the Project Gun with little effort.

What I did notice in my less than scientific trials, was on both the HA rifles, with extractors removed ( as well as firing pins), the bolts would JUST click closed with the slightest of resistance, when the bolt locks up against the locking shoulder and a round was inthe chamber. Like I said, not scientific, but I was feeling better about tolerances in the two HA Guns. One is in .303, one is an L4.

So that is where things stand. I will try the locking nut switch first, then probably order .7.62 gauges, then if all feels good, maybe try one of the .303s in 7.62. Still need to get some brass sheet and silver solder and make the modification to a few ZB mags.

With multiple projects, little range time and a confusing array of issues to resolve, I am lucky to be making any forward progress at all

I need some material to restrict full compression of the mag spring in the L4 mag and I will only expect to load no more than 27 rounds. I wish I could nest a spiral spring along with the flat leaf spring, even if not the same full length, and give the follower a little extra push, especially for the last few rounds or so. Don’t think that is the right way though, as a spring as long as the original would take up too much space in compression. And a short one does not do much by time the flat spring is fully extended in a nearly empty mag. Expanding block of foam? Rubber grommets? Or just put a solid block of something in the base of the mag to give the ole flat spring a little more push near the end?? Ideas?

My Mk II is a Wise Lite build and I have 5 .303 barrels that all fit the receiver using the same barrel nut and head space correctly . The GunParts, South African .308 barrel as noted earlier had no problem with barrel nut fit or head spacing . I have head the receivers rewelded by HA and some others may have mag. wells too long in length, and the locking shoulders were reworked to get the head space right . How do your spare barrels fit for your HA receiver reweld ? My Mk II was built using IMA cut receiver that had the barrel nut socket intact and there was no issue with the locking nut fitting correctly .

I think I will attempt this caliber conversion on my SMG-built Mark II Bren gun. :)

Nice to see barrels finally available for .308. They're expensive, but well worth it in the long-run. I've already successfully converted a TNW MG-34 to .308 and have fired about 1k rounds down it without much issue so far outside of the usual teething issues seen in the TNW MG-34 semi-auto conversion. I will also have to acquire some ZB-39 mags.

What headspace gauges are people using to headspace their guns in .308? Will a Forster set work well?

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Originally Posted by Syntax Error

I think I will attempt this caliber conversion on my SMG-built Mark II Bren gun. :)

Nice to see barrels finally available for .308. They're expensive, but well worth it in the long-run. I've already successfully converted a TNW MG-34 to .308 and have fired about 1k rounds down it without much issue so far outside of the usual teething issues seen in the TNW MG-34 semi-auto conversion. I will also have to acquire some ZB-39 mags.

What headspace gauges are people using to headspace their guns in .308? Will a Forster set work well?

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Yes a Forster head space gauge set will work . The go gauge at i.630 is what you are looking for the bolt to close on . And the 1.634 gauge is the no go for the bolt not to close on . See JOE H's information listed in this tread for the correct way to head space the South AFRICAN .308 barrel for use in a Bren chambered in .303 .

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Originally Posted by tr63

Yes a Forster head space gauge set will work . The go gauge at i.630 is what you are looking for the bolt to close on . And the 1.634 gauge is the no go for the bolt not to close on . See JOE H's information listed in this tread for the correct way to head space the South AFRICAN .308 barrel for use in a Bren chambered in .303 .

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OK, ordered a set of Forster 7.62 NATO sets at Brownells and the. 308 barrel from Numrich. Here's hoping that the barrel fits with my existing barrel collar and headspaces correctly without any issues.

Got my SA barrel and it seems like the bolt is able to barely close on a 7.62 Field gauge. :(

Looks like I should probably swap out the locking shoulder for a bigger one assuming mine isn't already the largest shoulder installed in the gun already. How well-torqued is the screw that locks the locking shoulder in the receiver usually? Seems like it should be just a matter of unscrewing it, counterclockwise like is usual for screws, but just want to confirm that it's not some weird clockwise-to-unlock screw.

The locking shoulder screw is staked in . You can see it when you look at the screw inside the receiver . You must have a very well fitting large tip screw driver the receiver should be clamped in a padded vice and be very careful in the way you try to move the screw . If you destroy the screw you can get a replacement from BRP or GUNPARTSCORP . How is the head space you not have with the existing barrel ? Maybe JOE H can offer some advice as to how best to remove the screw .

I haven't checked the headspace of the gun with the original .303 + bolt combination, but I imagine it should be good as I've fired hundreds of rounds through it already and don't have any signs of bulged cases or torn heads. This is Greek HXP .303 I've fired through it, along with some Prvi-cased reloads I've tested.

I'm thinking I probably shouldn't mess with the locking shoulder if I want to maintain the .303 British headspace with the bolt and barrel that was originally supplied with the gun from SMG.

Would a better solution be to utilize the spare L4 bolt I have for 7.62 NATO and do the semi auto cuts for the side of the bolt by milling the channels away, and then shaving the bolt face and/or the locking shoulder surface a few millimeters in order to fit it into my gun and do it slowly until perfect headspace is achieved? I know that the L4 bolt is slightly longer than the .303 British bolt by 2-3mm, but it would also have the added advantage of having the cartridge head recess on the bolt face be perfectly sized for the 7.62 NATO round.

Some one above my pay grade will have to chime in on the L4 bolt use .

Syntax,

If it is correctly head-spaced it should not close on a Field Gage. It should close on a GO gage which is shorter and not close on a NO-GO. The Field Gage is longer than both the GO & NO GO and is used for checking existing firearms for excessive headspace. If it closed on a Field Gage it should not be fired.

Use only the bolt for checking HS no springs or extractor. The bolt is extremely hard, I wouldn't mess with it.

The 7.62 nato headspace is looser than the .308 Win.

The locking shoulder screw is staked in an may require a pencil grinder to relieve the punches for removal. It is a right hand thread.

I'm not sure you have any problem.
Joe

Hi Joe,

That's the thing, it does barely close the bolt with a field gauge (7.62x51 NATO Forster Field gauge, 1.6455", found here: NATO Chamber Headspace Gages - Forster Products), so it's unsafe to shoot normal ammo as it is right now. I guess the "easy" path is swap out locking shoulders (or use an L4 locking shoulder and hope it headspaces) and exclusively shoot .308 out of the gun. I would like to maintain the .303 option, hence maintaining the current locking shoulder and machining the L4 bolt somehow. Is it so hard that even carbide bits won't be able to scratch it? I figure just go very slow and methodical in shaving it down to fit, if I can, on the locking shoulder side as that's less material than the bolt face side.

You really should check your head space on your .303 barrel with the existing locking shoulder . You might have a too large head space now . As you know the .303 round may work in the Bren Gun that is out of spec. head pace .074 max. Who build your Mk II Bren ?

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Originally Posted by tr63

You really should check your head space on your .303 barrel with the existing locking shoulder . You might have a too large head space now . As you know the .303 round may work in the Bren Gun that is out of spec. head pace .074 max. Who build your Mk II Bren ?

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Syntax,

Good point from TR63. The .303 British is very forgiving regarding loose headspace due to the length of its solid head. Not surprising that you have not had any problems with the .303. The 7.62 Nato and 7.62 x54R are much less forgiving.

I put a 7.62 SA barrel on my properly headspaced .303 and it checked out for 7.62 Nato. No problems firing.

The easiest way to fix loose HS is to get or make a longer Locking shoulder and grind back as necessary to get the correct headspace. If I remember correctly the standard length is .812". The LS should be hardened.

Brp has longer ones you can use to to get the correct headspace . You can make a new one, TIG weld 4140 on the face of the old one and grind back, slot the LS and shim the back. You can check your Locking shoulder but I think the grinding angle is 25 deg.

30: Bren Locking Shoulder (specify size 2x or 3x) - BRP CORP

Joe