54R Bren Issues

[Peter Laidler]

Just a couple of things - this has sort of whetted my appetite a bit in a strange way. I appreciate Joe's straight talkin' approach and the photos certainly show that there's plenty of meat in the case where the extractor slot is. I accept that if .303" brass ain't blowing out (and never has) then 762x54 steel should eaasily pass! But why. There's a simple answer coming up......

Djan.... I take the point and I agree about the cheapest ammo but when you go down that route, there is a chance that you will encounter a problem. And here it's a mechanical one. I don't agree that there ISN'T proper support because we've already shown/proved with 90% of the rounds and a lifetime of .303 rounds fired that even though there is an extractor slot, there definately IS proper support and the shell casings CAN support the load.

BUT......., some of them cannot support this. I would be finding the ammo type/make that WAS capable of supporting the load without splitting/rupturing and then concentrate on that ammo.

When you say 'the low spot' DJ, what do you mean? There are two 'low' spots on the rear face of a Bren barrel. The top 'low spot (1st and 4th photo) is to allow the slightly overhanging breech block feed horns a running clearance but clearly this isn't anything to do with your prob. Then there's a low part at the bottom of the barrel (2nd photo) the area of which is the cut-out that's causing the weak case to blow out. You can't do anything about this because it's the extractor way and the extractor on a Bren gun is a wonder of mechanical complexity because due to...... Do you want a slightly technical classroom lesson........ ? Anyway when the case is fully chambered and about to fire, the piston extension loosens its 'grip' on the extractor stay and loosens up the extractor on the about to be fired case.

Then after it's fired, the piston extension moves slightly rearwards and causes the extractor stay to REALLY tighten up on the case......... Now something else happens if you're following me....... The tight extractor is still gripping the red hot fired case as the breech block starts to drop down at the rear at commencement of unlocking and as it does, the lowest points at the face of the breect block violently rocks/rotates on the breech block stops in the gun body ( a major test by Armourers for worn guns) and the front rounded surface of the still tight extractor rocks on the extractor way in the barrel. The fired case is just gently rolled a gnats knacker to the rear and this gentle rolling motion just breaks the tight taper obturating seal of the case in the chamber. Now as the breech block has reached the unlocked point, it can move violently rearwards taking the loose case with it. In fact, it's SOOOOO violent, if the firing pin didn't punch a huge oval dish into the primer to swell it up and the ejector didn't additionally stake it in place to make sure, momentum would be freeing the primers out into the guns and causing jambs

That's why we rarely ever get ruptured cartridges in Bren guns. We DO of course but while the main extraction and ejection is violent, the actual PRIMARY extraction is a very quick, rolling leverage motion. That's why you can't weld up the hole or change the size to suit.

Sorry it's been a bit long winded...................