Repairing Bren Mk 1 barrel

[Peter Laidler]

Our ideas are what we call '.......same meat, just different gravy' Joe. The only reason I say use an old rifle chamber is that it is already a known quality and dimensionally correct and therefore cheaper and on the face of it, simpler of course because all the metallurgy and chamber cutting is already done for you. Just my take on K.I.S.S. of course. On the other hand you could use a shot-out Bren barrel stub to achieve the same result. The good bit is that if it should fail, then you just pull the insert out and start again.

The theory of both methods is absolutely sound as our original FN-MAG58's L7/GPMG's came with chamber inserts*. Not only that, even today, the enlarged section at the rear...., the bit that holds the barrel locking nut and carrying handle is a pressed on part and pinned

Bren and rifle barrels are a pleasure to machine with good cutting tools but I feel this idea of plugging as in the drawings shows a degree of, er......., what is the most diplomatic way I can put this......? Anyway

*As mentioned earlier, it failed for OTHER reasons and not through gas leaching or the insert moving

Have a nice rest of the day Joe from Abingdon in Oxfordshire

[Joe H]

7.62mm barrels. Richard........, this forum is littered with peoples day-dreams of producing them....... and others day-dreams of buying and owning them. And which version of the 7.62mm barrel version of which 7.62mm gun do you want? Guess how many have succeeded so far. Call me defeatist if you like but having used, repaired and worked on them with a megga deep understanding of the design and build, I say that UNLESS you stick to or retain the exact exterior profile and alignment of an original known barrel, it ain't goin' nowhere. Just my view

Richard,

I know of only two L4A3 7.62 barrels that have sold in the US in the past 10 years. Both around $1,000 USD. South African 7.62 barrels show up occasionally at more reasonable prices.

Recently L4A3 kits have been available but without barrels because of import restrictions. The seller promised new made barrels would be available shorty for $100. That was last December. No sign of barrels yet.

I bought one of the kits with full knowledge that I would probably have to make my own barrel. It is definitely doable with a typical reasonably well equipped hobby shop with manual machine tools. I've got the un-chambered 7.62 blank ($55 USD). The blank is 1.25", a hair smaller than the 1.26" (32mm) of the original but it will work. I have a 13" Clausing- Colchester lathe which is capable of the 7mm pitch interrupted thread required on the barrel. I did have to order a 30 tooth splined change gear. I got it from RDG tools in the UK. Once you have the threading it's a matter of making a simple index plate with a rotary table and you are ready to machine. Not cave-man simple but doable if you have reasonable machining skills. Alternatively, you can shrink on the threads from a scrap Bren barrel (any Mk) on the blank if you can't do the threads.

Joe

[Joe H]

Our ideas are what we call '.......same meat, just different gravy' Joe. The only reason I say use an old rifle chamber is that it is already a known quality and dimensionally correct and therefore cheaper and on the face of it, simpler of course because all the metallurgy and chamber cutting is already done for you. Just my take on K.I.S.S. of course. On the other hand you could use a shot-out Bren barrel stub to achieve the same result. The good bit is that if it should fail, then you just pull the insert out and start again.

Peter,

.303 Rifle barrels are not readily available here in the US but Bren barrels are. The Bren stub is a great idea. The only issue is that it has to be aligned properly when you shrink fit it.

Joe

[Richard-]

Fine, I'm convinced now!

I'll shrink a sleeve into the barrel and re-machine the chamber.

Thanks for the input, all.

I'm working with a guy who's a precision machinist and gunsmith, he has access to a CNC lathe so we will start off the L4 barrels on that and see how we go.

In Australia, nothing is available. I've only seen one .303 Bren barrel in the last three years, and that was well-worn and shot out for $3,000. Just the barrel.

Cheers,

Richard

[Peter Laidler]

I mention rifle barrels because it's rare that a chamber would be shot-out or worn out - or whatever else will knacker a barrel doesn't usually affect the chamber so on that basis, there will (?) be knackered barrels with good chambers available in the US and Oz. I had 2 to practice with.

As I see it, if the chamber of your Bren barrel is absolutely concentric, which is simple to ascertain, and you machine the barrel stub using the clamber as the centre instead of the O/D as I mistakenly did, then theoretically you shouldn't need to re-chamber or even skim it out.

Making a good L4 barrel is the first bit. But it's the barrel locking nut threads ability to lock-up with the barrel locking nuts available, which datum you are working to, what breech blocks you have, locking shoulders. The inter-operability/reaction of all these parts working together to set an L4 or Bren up PROPERLY was a nightmare.

Lithgow made their own L4 barrels by getting around a so-said badly worded part of the patents and contract. They couldn't work the same trick with the UK curved 30 round magazines but the straight L2 rifle mags worked perfectly in our UK supplied L4's. What all this is saying is that the drawings for L4A4 type barrels will be in the old Lithgow archives '......somewhere!'

[Richard-]

Peter - the L4 barrels I am making will be made from a combination of a drawing of an L4 barrel profile, and measurements taken from an L4 gun itself.

So they will be made to fit, basically - they may not interchange with another L4, but they won't have to, either.

That is interesting re: Lithgow and the L4 barrels.

I have a few curved L4 marked magazines - I thought they were Australian made, doesn't sound like it! I will have to re-check the markings.

[Joe H]

Richard,

Are you planning on using the .303 bolt and locking shoulder with your "L4" barrel? If you are, the rear of your "L4" barrel must have the same dimensions as the South African 7.61x51 barrel or your .303 bolt & locking shoulder won't work. The L4 7.62 x51 and 8mm Mauser Brens had a different bolt and locking shoulder that prevented inadvertent chambering of the .303 in the 7.62 Nato or 8mm gun. The South African version used the .303 bolt.

I have a 7.62x51 south African barrel which can be used interchangeably with a .303 barrel without changing the .303 bolt or locking shoulder in my semi-auto.

It will be a major operation requiring some very unavailable? parts to convert your Mk I to use the L4 magazine. IMO converting the Bren to use the L4 (FAL) 30 rd mag was the main reason the conversion was so complicated. The mag well of any Bren MK gun can use a ZB39 mag or be easily modified to take the 8mm Zb 26-30 mags. Either of which will work with 7.62x51 Nato.

I guess a lot depends on what mags are available "down under"

Joe

[Peter Laidler]

You are soooooooo right JoeH. The changes required to accommodate the L4A1 magazine were complicated enough. But for the L4A2/big-lug magazine, in the words of one of the engineers involved in the project.....
“…we used and ruined a LOT of Bren bodies”
Designer involved in conversion project to Author
In this configuration, the front retention knib of the new magazine would not only have to intrude into the front face of the magazine well but the machining would also break into the hole occupied by the barrel nut retaining plunger and spring. It gets worse! One designer involved in the project rolled his eyes and looked skywards in desperation and exclaimed “…we used and ruined a LOT of Bren bodies…, it caused us nightmares. We were working from drawings and the problems were not immediately apparent. The actual mechanics of it were only visible when we sectioned an actual body. The answer when it came was simple, “…we simply bored through into the spring hole and used a vertical pin on which to seat the spring!” This was the breakthrough that the re-designers were looking for and a cross sectional view of this method is shown in the accompanying engineering drawing. For the first time, the gun would feed from the new magazine. The only thing left now was to secure the magazine to the gun. Remember that now, the rear of the new 7.62mm magazine was situated 1 “ further forward than the original .303” magazine so using the original magazine catch was out of the question........

It goes on for several more pages. And on that basis alone I have disputed anyone to back engineer the .303" magazine interface to 7.62mm L4A2. But a couple have done it! It does emphasise the fact that getting a weapon to fire a different cartridge is simplicity itself. But it is the other parts of the equation that are difficult. As Enfield discovered with the Bren L4 and those hardy souls trying the same from .303" to 5.56 in their rifles are finding out

[Richard-]

Joe, Peter - fortunately, I have a second Bren L4A3 gun in as-new condition that just needs barrels.

Everything's possible if you wish hard enough!

[CINDERS]

Peter ~ In a practical sense converting the Bren to fire the NATO round was that borne from a suitable replacement weapon being sought with that I guess I am saying the replacement had been found but the feet were dragging as bean counters do and it was to be a while before the replacement was in sufficient numbers. Was it so difficult to keep the 303 cartridge going until the NATO firing replacement was fully implemented or was the Bren outdated for field use, I mean it was built like a truck and had seen allot of service with various armies around the world or perhaps were there bigger moves afoot just asking your opinion on the matter.