54R Bren Issues

Thanks guys. I do want to get the rifle set up correctly first before I blame the ammo. IF it is firing out of battery or whatnot, using weaker brass casing than the steel will not help. Steel is WAY stronger than brass. If I am relying on unsupported brass to contain a .30 explosion, I'm nuts.

As for the shoulder, seems like most folks agree machining is necessary if I can't find one the right length. (and not having much luck so far) I don't have the necessary equip. and experience. But I will be happy to ship the shoulder and compensation to those who do (and can do it rather expeditiously).

Any volunteers?... Any conscripts?

Thanks,

It will not be a sure thing... but I'd contact Mark Graham.. of Arizona Response Systems... he's a really good guy and one heck of a fine gunsmith... I know he has the shop and know how to do this work... but a semi Bren is not his normal subject matter. He is highly regarded as an AK and FAL builder and the FAL uses a locking shoulder for CHS... so I'm confident of his ability. He might want to read this thread to get some context of what you are up against and the expert commentary provided on the possible solutions.

Aside a bit DJ and your comment on brass v steel case. Then yes, steel IS stronger than brass as a material BUT we are talking about steel v brass in an APPLICATION of a metal. I usually follow up with a car related engineering example but can't think of one off hand except to say that brass is FAR more pliable and resilliant. And this is exactly what you need for cartridge cases. It is also a superb method of taking heat out of the gun (easy test for students to test, experiment with and write up.....) although this isn't a feature in this instance.

Near as I can reference without getting to exact specific alloys, the mild steel used to make cartridge cases has pretty much the same yield and ultimate tensile strengths as cartridge brass. If the steel wasn't of very mild alloy, it would not take the deep draws required to form the finished cases.

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Originally Posted by TactAdv

For my original select-fire BREn, I am in the process of making two caliber conversions- one, 8mm using one of the mystery re-bored and chambered original .303 barrels that are floating around out there, and two, a .308/7.62mm NATO conversion using an SA 7.62mm barrel. Both conversions will use standard, original .303 bolts with 7.62mm extractors installed. (Magazines are ZB26/30 mags for the 8mm, and ZB-39 mags for the .308. The ZB26/30 mags require a slight opening up of the rear mag well area.)

Both barrels are fitted to lock up tight and smoothly in the barrel recess in the receiver; at that point, current (-ANY-) "headspace" of the chosen bolts with the installed locking shoulder is irrelevant as each bolt will be hand fit to mate properly with it. The goal is to make each conversion such that all that is required is to field strip the gun, exchange the barrel, bolt, and magazine, leaving the installed locking shoulder and all else in place.
(I have also a 7.62x54R conversion "mostly" done, as I have previous mentioned, though am currently stalled on the magazine.....I have decided the only rational plan is using a modified DP-28 47rd pan, modifying the underside receiver interface to fit and lock in the BREn receiver. Got most of that done, but will still be awhile to get it fully fitted.)

-TomH

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Tom,

To make a longer LS I was thinking about adding weld to the LS and grinding back but had the same reservation about welding on the hard bolt, cracking. I just ended up making a new LS.

Have you tried welding the bolt yet. Technique and type of rod?

I've done the same conversions for my semi MK II. I had a .303 barrel re-bored and re-chambered for 8mm Mauser with headspace set so that the rear face of the case was in the same location as the rear face of a .303 British rim.

I have done the 7.62 x 54 r conversion. The converted bolt also works and headspaces with the .303 British. The 54R bolt also works with a ZB39 barrel and the 8x56R. The 54R mag issue is another story. I have a few ZB39 mags. I found one the works with 20rds of 54r:confused: , the rest will only work with about 13rds. By using a helper spring, annealing a few leaves of the leaf spring, and some other mods. I was able to get reliable feed of 25rds of 54R in the ZB mag.

My 54R bolt also headspaces with the 7.62 x 51 Nato and the 8mm mauser. Interestingly either will cycle with the standard .303 British extractor. Haven't live fire tested yet they hand cycle reliably :D .

Maybe I got lucky, hopefully, just change barrel and mag for different calibers. My bolt and Locking shoulder works for all.

I also noticed that the 20 rd ZB26-30 mags will only work with 19rds semi-auto. With 20 rds they have no space left for the bolt when retracted to push cartridges up further in the mag. 20 rds for FA open bolt only :eek:

Joe

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Originally Posted by djandj

As for the shoulder, seems like most folks agree machining is necessary if I can't find one the right length. (and not having much luck so far) I don't have the necessary equip. and experience. But I will be happy to ship the shoulder and compensation to those who do (and can do it rather expeditiously).

Any volunteers?... Any conscripts?

Thanks,

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Djandj,

Just do it yourself with a stone or emery paper and a flat surface. Yes it is a bit tedious the first time. Easily less than an hour and as Peter said easier as you get the hang of it and its pretty difficult to screw up by doing it by hand:D.


Joe

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Originally Posted by jmoore

Near as I can reference without getting to exact specific alloys, the mild steel used to make cartridge cases has pretty much the same yield and ultimate tensile strengths as cartridge brass. If the steel wasn't of very mild alloy, it would not take the deep draws required to form the finished cases.

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I think a brass case is actually hardened and stronger as a result of cold hardening when the case is formed. The case neck is always annealed (heated and left to cool) so it is softened and will not split. This is the discoloration you see on the case necks of military ammo. Commercial manufacturers usually polish after annealing so you never see the discoloration. The case head is left hard and should never be annealed.

Joe

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The case neck is always annealed (heated and left to cool) so it is softened and will not split.

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:thup: And it helps the case obturate when the round is fired.

I never thought of steel as better or stronger than brass for cartridges. I always viewed it as a poor second or substitute. It's not really steel anywayzzz...it'll be a softer mixture.

That's a very valid point BAR. On the same track, then surely if steel was as good as brass, we'd ALL be using it. But it's not. As you say, a reasonable good substitute.

I say that DJ ought to at least try a mag full of brass cased stuff, even if it is to eliminate the steel case proble.

Incidentally DJ, did any of the successfully fired steel cases show signs of belling outwards at the unsupported extractor way part?