Semi-auto Bren piercing primers - any solutions?

Hi guys,

Anyone have an idea for a solution to this issue?

(It is a US civi-legal semi-auto Bren, using the striker system, not an open-bolt Bren.)

I am using the recommended S&B ammo - Bren is cycling nicely but rupturing the primer.

Thank you in advance for any suggestions.

*I'm going to try out some surplus Brit .303 ammo, that has tougher primers, hopefully that is the fix. I'll also try it with some PPU ammo.

https://www.milsurps.com/images/impo...iZFy89cl-1.jpg
https://www.milsurps.com/images/impo...JLRFonFl-1.jpg
https://www.milsurps.com/images/impo...3lQlHH0l-1.jpg

We often equate that sort of thing to excess pressure in reloads, that's factory ammo isn't it? I always thought S&B to be at the very top of the pressure curve in it's loadings.

Otherwise it would be firing pin protrusion, but there are guys here that can quote you what that should be off their noggen...

Thanks Jim, this was 100% new manufacture factory Seller & Bellot ammo.

Yes, I posted in several forums on this question, as I really don't want to damage the Bren, apparently you are correct S&B are hot loads with weak primers.
I'm going to run some WWII Brit through it, and some PPU next week, heat that old barrel up and see what happens.

Thanks.

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Originally Posted by dcollector

WWII Brit through it, and some PPU next week,

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Those should work fine if the WW2 ammo fires when it should. CCI makes military thickness primers I think...but I expect you just want to shoot factory. As for hurting a Bren, I loaded an old reload into an Inglis 8mm once...another man's gun and his cheap ammo gatherings...and when it detonated the mag turned into a tube launching the base and spring. The case was destroyed, the gun was unhurt. Functioned well as if nothing happened. Peter L will be able to give us some sage advise here if he sees this post.

Perhaps the firing pin is insufficiently supported, allowing the metal to be blanked back into the firing pin hole in the bolt face.

The Bren firing pin is designed to stake the primer in the pocket after firing to remedy the problem of backed out, spent primers jamming them during trials. I don't have much experience with S&B but guessing if you change ammo, the problem will go away.

Never seen that with any Bren but caps-out was a problem until they solved it, as Brian says, by staking the cap in place during ejection and knocking the cxxp out of it, to distort it when firing.

Could the striker hole be enlarged? Failing that, the answer must be excess pressure blowing back against a weak primer.

I did see a Bren accidentally fired without a locking shoulder. Te breech block was not locked up so came back and split. The magazine and rounds went upwards and onwards and are probably still in orbit around the moon. The blast from the round exploding in the breech caused the body to bulge and the gun being written off.

The locking ramp at the rear of the breech block ran hard into the rounded rear shoulder of the empty locking shoulder housing and stayed absolutely locked into place. So there was no excuse or waffle explanation that could explain it all away. But as the person who left the locking shoulder out was a young REME Craftsman, The Field and eventually, Base workshops were able to send it on its way to the great scrap yard in the sky. After all......., dog doesn't eat dog.

Took The Bren MKII Semi out to the range again today.

Ran three 15 round loaded mags of S&B through it, no pierced primers.

However the last mag experienced a case separation, and of course I had left that particular tool at home.

I bought 200 rounds of PPU, and some newer British military issue ammo to try, too.

But, not another pierced primer.

I shot my two revolvers for the rest of the outing, they were a lot of fun.

https://www.milsurps.com/images/impo...ti562lTl-1.jpg
https://www.milsurps.com/images/impo...5QjiV0vl-1.jpg
https://www.milsurps.com/images/impo...RyMnmyxl-1.jpg
https://i.imgur.com/eQnRmIbl.mp4

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Originally Posted by dcollector

a case separation

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I expect you'll get one every so often.

Yes, it was a firearm designed, tested and R&D'd successfully to shoot from the open bolt in primarily full auto.
That has been converted to a closed-bolt operation, firing "semi-auto only" via a striker/impact system, that has never been used by any military or even successfully commercially produced in any real numbers, with a re-welded receiver, often made of multiple guns parts - usually by an engineer who does the work in his spare time.

After talking to a lot of owners, there is no real uniformity to these rewelds, some of these run perfectly, these appear to in the minority.
The Historic Arms ones seem to be the most consistently reliable and nicer looking re-welds, but even those have some kits that just never work perfectly amongst them.

I have learned:
Most SA only Brens require a certain amount of tuning, and will prefer some ammo over others, there will be issues, you should always bring a selection of mags, and cleaning tools; split case remover, chamber cleaner, gas-pipe/piston cleaner, lube/oil with you.
The chamber shouldn't run dry, and some .303 ammo fouls more than others, some is made with thinner brass, some are loaded hotter and some propellant is just unreliable and inconsistent due to age or manufacturing.

But, the Bren is a lot of fun to shoot, and it will be going out to the range again - it's ugly (receiver welding) and I've now spent years waiting, and paid three different gun-smiths to tune it, so it will never sell for what I've spent thus far, so I have decided I will shoot the tar out of it, lol!

The MKI will be back soon, and I'll do a range analysis of both guns together.

*I am seeing there is a separate posting area are for the "Semi-Bren" - I sincerely apologize for not seeing that and posting here. It also appears this research has been found and similar conclusions drawn and arrived at.

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Originally Posted by dcollector

the Bren is a lot of fun to shoot

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Yes they are. I had one here in .308 and we shot a mag or so of tracer at 200yds. It was like having a red light appear on the target as you were about to shoot...

Quote:

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Originally Posted by dcollector

I will shoot the tar out of it

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Yes, best way to go. Just keep it and use it.

Forty-plus years ago I experienced numerous "ripped open" primers exactly like the ones you have shown. Mine were fired in a very well-worn two-dovetail Mark 1 full-auto gun with a Mark 1 barrel. The ammo was military surplus .303, I believe from India or maybe Pakistan. Best as I recall, the headstamp was K 50 (Kirkee?). The ammo was imported by FedOrd in California; I bought a full steel case of 3,000 rounds loaded in single-use Vickers belts. The cartridges were very clean Mk VII; I broke a couple down and found them loaded with cordite. The gun functioned fine, but the peeled-up primers obviously were not good for the bolt face, and neither the cordite nor the corrosive primers had much to commend them.

As to cause: right off the bat I blamed the ammo: seasoned (and therefore brittle) primer cups. Later, after some separated cases, I followed the procedure in the Armourers’ Wing Précis SA/7, and discovered that the gun had considerably excessive headspace; inspection also revealed a broken piston post buffer spring. What if any role these latter two played in the torn primers I cannot say, but I suppose it is possible that the broken spring did not properly support the firing pin after cartridge ignition, and perhaps the extra headspace gave the primer more room to tear.

Anyway, I quit using that ammo. A larger locking block cured the headspace, and the broken spring was replaced. After that the gun worked extremely well.

That’s primer flow back into your firing pin hole. I built a 3006 Italian bren and ran into the same issue using the firing pins.com pin. I had to make a longer one that sat just shy of the face of the bolt. Continued firing will damage your bolt fade and firing pin hole as well as the pin.

I forget how to load photos or I would post a few

Dropbox

Dropbox

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Originally Posted by Cetme24

I forget how to load photos or I would post a few

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I'll put them here in clear for you...pics from Post#14.