Need forum help - 147 grain 9mm in suppressed M76 incident

[Rekraps]

I own a M76, unmodified. Have shot the gun for several years, no issues. Today, i went to the range and mounted an Obsidian direct mount 9MM suppressor. Using factory Winchester 147 grain, flat nosed bullets, i shot about 1/2 of the magazine, no issues. Then the bolt cycled accompanied by an obvious flash of gunpowder out of the ejection port.

 

I looked into the chamber and all that remained of the casing was the very end (about 1/16th inch), lodged into the chamber at an angle. I removed the barrel and using a cleaning rod, was able to clear the barrel. What came out was the bullet, and the remainder of the shell casing.

 

Now, the bullet was in perfect condition, and there was only one, so a squibb is not the issue. The bolt is undamaged. What i think happened is that the round detonated before being fully seated in the chamber.

 

Since this is a recoil operated gun, when the round exploded the bolt simply cycled and the gases expanded out of the ejection port. (Yes, I was wearing glasses). There were brass shards everywhere.

 

I removed the suppressor (perfect condition) and ran the rest of the ammo through the gun, no issues.

 

A couple questions for the forum:

 

Has anyone had this happen to them?

Anyone heard of issues with 147 grain flat nose feeding issues in a SMG?

Anyone have any ideas as to what may be the issue?

 

I am beginning to think that the flat nose 147 maybe did not feed smoothly, got hung up just before in battery and the force of the bolt moving forward fired the round.

 

Ideas? Comments?

[ranger1385]

I had something like that happen. But not my M76 with suppressor. The bullet got stuck in the barrel and the case separated kinda like yours. I thought it was a bad reload. Hasn't ever happened again. Luckily the weapon wouldn't chamber another round.

[Mike Hammer]

I’ve shot 147gr flats in my suppressed Mac 11 with never a problem. Is that the 76 you just added the stock to? Is this the first time that you used the suppressor on the gun?

[Frank Iannamico]

The only time I had a similar problem was when there was a previous round stuck in the barrel. Check for a bulged barrel.

[Rekraps]

Same gun! I've used a suppressor many times with 124gn, no issues.

 

This may be a one time event.

[Rekraps]

Maybe Covid-19 related?

 

[BillyDixon]

any chance the over all lenght of the 147 bullets is a slight bit longer than the 124 bullets and fixed firing pin is hitting before case is fully chambered,?? just wondering

[tomk]

Once had a squib with Winchester "white box" 9mm. Only 1 round left in barrel and slight ring in barrel. Used a rod to pound out the stuck round. Was with an MP34. Easy barrel change thankfully. Same experience - flash out of ejection port and brass was half there half somewhere else. MP34 is built like a tank.

 

I had some "truncated cone" 147gr ammo (don't recall brand) in a Swedish K that did not feed well. That's the only ammo that it did not feed. Ever. It is usually just a garbage disposal for whatever it gets fed. I've since had the gun reworked and don't recall any issues using Swedish K and 147gr Speer Lawman (small flat on bullet tip). I also don't recall if I had an out of battery kaboom or if it was just getting hung up feeding and pushing bullet awkwardly into the case. I think I would've remembered another OOB so maybe I stopped using it before that happened.

[Rekraps]

Thanks for the ideas. I'll certainly measure the rounds and compare to the 124's.

 

The great thing about these open bolt guns (including K's, Lanchester, M3's etc is that if by chance there is a Squibb, the chamber pressure will push the bolt back before any damage, since the bolts do no lock into battery.

 

I have made it a rule that I only use factory loads with SMG's, never want to take a chance.

[hkg3k]

In my experience, truncated cone profile bullets do not feed well in dual-position feed magazines. They work fine in pistol mags and other single-position feed mags like M11/9 mags, STEN mags, etc. Straight shot to chamber vs angled path.

 

You mentioned the bullet was perfect condition...did it have any rifling engraved on it? If not...that would be definitive evidence IMO that you had a OOB vs a squib.

 

My suggestion would be to stick to round-nose profile bullets...they're available in 147gr, just not as common as the truncated cone profile.

[Haenelistklasse]

I think it was the fact that you were using flat nose bullets. I only use the round nose period.

[StrangeRanger]

FWIW my Uzi will not feed NATO spec 124 gr. flat points

[rbtf70]

My Uzi hates the flat nose 147s. Had a couple of cases and sold them during the early part of the current ammo crunch.

 

Reloaded a number 147 RN FMJs using a relatively fast powder to avoid un-burned powder in the suppressor, but recently switched to 165gr plated bullets from X-treme bullets. The Uzi and the suppressor both love them.

 

Avoid the flat nosed stuff.

[Rekraps]

After a ton of thought, and your feedback this is what I have concluded. I had an OOB event, caused by the combination of flat nose 147's difficulty in feeding smoothly, and a fixed firing pin on the bolt. The round did not feed well and the bolt kept pushing causing the modern ammo primer to detonate.

 

Advice appreciated, I'll stick to round nose 147's.

 

Thanks again to all who read, and to those who responded.

[Roland the Thompsongunner]

I had this happen a couple times on my Ppsh41. What happened sure sounds like out of battery. I had it happen with two different brands of ammo that I do not use in the gun any more.

[Rekraps]

For my PPHS i only use hard primer military 7.62 x 25. Thing shoots way too fast to allow any chance of a problem.

[Roland the Thompsongunner]

I shoot my PpSh a lot in 9mm..well at least I used to when ammo was affordable. I stick to Winchester, Prvi, and S&B mostly

[omegaman]

Mine hates flat nose. Have had issues with cases stretching out at the base until i started loading with a slower burning powder.

[Rekraps]

Wow, I stay away from any reloads with SMG's... only because a squib would ruin them. I guess if you reload yourself you have better control over quality.