54R Bren Issues

[Joe H]

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H&K’s fluted chambers are notorious for stuck cases. The Sig’s chamber flutes are not as deep, so it’s a bit more tolerant of different ammunition. But the whole fluted chamber concept adds a degree of complexity that’s not necessary and reliability suffers as a result.

A hard extracting, over gassed long stroke piston gun will run like a top on any ammunition. Yes, it’s crude. There’s no fancy over engineering, just brute force extracting the case. But who can argue with the reliability of the AK and PKM? And while not as over gassed the FN MAG, M1 Garand and the Bren are some of the most reliable guns in the history of warfare.

Some guns are like fancy cars that need high octane fuel or they won’t run right. There’s nothing wrong with cheaper low octane fuel. They are just not made to use it. Putting steel ammo in a Sig or H&K is like putting low octane fuel in a fancy car. If you want burn that stuff, you need something like an F150 pickup that’s designed to run on it.

The Bren was not designed to use steel ammunition, but it operates very much like guns that were and it’s certainly robust enough.

IMO Vincent is correct. Djandj’s problem is not a subtle problem of “flow” or fluted chambers as has been discussed in the brass vs steel argument.
The chambers on the .303 bren barrels are large. Just look at the bulge on the spent cases just above the base. The chambers were sized for reliable extraction, not reloading. I would suspect a 54r chamber that was that “generous” would result in problems directly related to steel vs brass but the .303 bren barrel converted to 54r has the correct chamber dimension beyond the neck.
After the discussion of the relative merits of steel vs brass for cartridges I would, of course, prefer brass. On the other hand steel has been used successfully for years mainly spurred by military use.
IMO the use of brass or steel really is not the crux of Djandj’s problem. He currently has some brass Yugoslav 54r to try. If its 182 gr I’m not sure how it will work in a Bren. Has anybody used 182gr in a Bren? If he tries it without any problems does it really tell us it is a brass vs steel issue? If the brass ammo has a deeper solid head like the .303 British, he may not have any problem. If it’s the same as the steel 54r, it will blow if it experiences the same conditions as the blown steel 54r.
To me the difference could be in the construction of the cartridge head. IMO the only way Djandj’s cases could rupture as his pics above show is that they are experiencing pressure after having moved to the rear, or are too far back when fired, and the thin walls have cleared the notch in the barrel. A short case head could cause this. This could easily be determined by x-sectioning one of the blown cases and comparing it with the good cases. This would be an ammo defect. Loose headspace could cause it but per Djandj’s analysis the HS is, if anything, too tight. Another explanation in a semi is that the bolt is unlocking too soon, the case if moving rearward before the pressure has dropped. Anything else???
My 2 cents,
Joe