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2/4/2024 8:04:27 PM EDT
Shooting my m11/9 today and had a failure.

It was running fine and then a strange pop and noticed less recoil.  The bolt was stuck forward with this shell in the chamber.

I popped the upper off and had to pry the bolt out of the upper, the extractor was locked onto the rim really good.

Then the case was stuck in the chamber.  I used the antenna on my truck as a ram rod and after a ton if force I got it out as shown.

The primer has a hole clear through it. The case is swelled and the primer looks like it was blown back into the bolt.

There were no obstructions in the bore, and everything seemed OK after, I ran it some more without any issues.

When this happened it didn't sound normal instead of a POW it was POP with tons of smoke coming from the magwell and upper.  I was shooting suppressed so it wouldn't be that loud anyway  but there was something different about it.

This is PMC Bronze 115gr new mag.  I just got this stuff last month, both a thousand rounds.  This is the first issue after several hundred.

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2/4/2024 8:14:46 PM EDT
[#1]
How did the round before this one sound?
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2/4/2024 8:37:18 PM EDT
[#2]
Good question but I didn't notice anything.  Are you suggesting a squib that was cleared by this round?  That's a scary thought.

I did inspect the can after and had no evidence of a baffle strike.

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2/4/2024 8:57:27 PM EDT
[#3]
I would assume it was a hot load or somehow got a double powder charge.
I'd contact the company and explained what happened.
Glad your gun didn't blow up!
2/4/2024 9:02:28 PM EDT
[#4]
There is a bolt imprint on the "M" on the case and the primer is flattened. In the reloading world that would indicate a HOT load. That shouldn't happen with factory ammo.
"What have you given us Mr. Franklin?" "A Republic, if you can keep it."
2/4/2024 9:08:47 PM EDT
[#5]
Quote History
Originally Posted By cjk:
There is a bolt imprint on the "M" on the case and the primer is flattened. In the reloading world that would indicate a HOT load. That shouldn't happen with factory ammo.
View Quote

Yikes!

So what kept the action from cycling, just the swelling of the case to the chamber?

I can send PMC an email if I still have any if the lot numbers left.

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2/4/2024 9:24:46 PM EDT
[#6]
I'd say way hot load. Or wrong powder. Normally a pierced primer means not enough primer support, hot load or too much FP protrusion.


Check your barrel and make sure the projo isn't stuck in there.
2/4/2024 9:56:21 PM EDT
[#7]
Quote History
Originally Posted By ggllggll:

Yikes!

So what kept the action from cycling, just the swelling of the case to the chamber?

I can send PMC an email if I still have any if the lot numbers left.

View Quote


Wild guess is the hole in the primer? This is beyond my expertise, Im just a reloader but good luck figuring it out.
"What have you given us Mr. Franklin?" "A Republic, if you can keep it."
2/4/2024 11:33:34 PM EDT
[Last Edit: Civil][Edited] [#8]
Post this up at uzitalk.com in the MAC10 sub forum as the m11/9 open bolt MG experts post there.

My guess:  a squib first followed by the round/brass pictured that overpressured the barrel but cleared the squib & second round.
2/5/2024 1:22:11 AM EDT
[Last Edit: engineer61][Edited] [#9]
Much too high pressure when that round went off. The primer isn't just pierced, it's also flattened around the edges that should be rounded over - compare to an unfired round to see the difference. The headstamp markings are flattened and filled in somewhat by the high pressure ironing them flat too. I doubt that it was a previous squib that caused this, typically when that happens it also bulges the barrel and the OP didn't say that happened; though he should probably check to make sure. I would guess the wrong powder was loaded into the cartridge, Bullseye or Red Dot instead of Power Pistol or W231 would cause these results.

Edit to add: OP check that the small circle of metal from the primer isn't blocking the firing pin channel, something that can easily happen with a pierced primer.
2/5/2024 3:25:03 AM EDT
[#10]
Factory ammo correct?  Not reloads correct?
2/5/2024 6:31:06 AM EDT
[#11]
Originally Posted By cjk:


Wild guess is the hole in the primer? This is beyond my expertise, Im just a reloader but good luck figuring it out.
View Quote


Yeah there's a hole clear through the primer like it's been drilled out.

Originally Posted By engineer61:
Much too high pressure when that round went off. The primer isn't just pierced, it's also flattened around the edges that should be rounded over - compare to an unfired round to see the difference. The headstamp markings are flattened and filled in somewhat by the high pressure ironing them flat too. I doubt that it was a previous squib that caused this, typically when that happens it also bulges the barrel and the OP didn't say that happened; though he should probably check to make sure. I would guess the wrong powder was loaded into the cartridge, Bullseye or Red Dot instead of Power Pistol or W231 would cause these results.

Edit to add: OP check that the small circle of metal from the primer isn't blocking the firing pin channel, something that can easily happen with a pierced primer.
View Quote


Will recheck the barrel but I didn't notice anything the first time.  Good point.

Originally Posted By Civil:
Factory ammo correct?  Not reloads correct?
View Quote


Correct PMC BRONZE and I found one of the empty boxes and sent an email to them last night with the lot number.


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2/5/2024 5:40:49 PM EDT
[#12]
Quote History
Originally Posted By engineer61:

Edit to add: OP check that the small circle of metal from the primer isn't blocking the firing pin channel, something that can easily happen with a pierced primer.
View Quote



Mac is open bolt. No FP channel.
2/5/2024 6:32:26 PM EDT
[Last Edit: peachy][Edited] [#13]
In my experience with open-bolt SMGs, I wouldn’t read too much into the case head being imprinted. That is just what happens in those platforms. Even weak 9mm ammo that will barely dribble out of my Uzi has far more pronounced stamping of the case head than that.

ETA: checked some .45 brass out of my M10, and it isn’t stamped. Maybe it is just an Uzi thing.
2/5/2024 7:23:37 PM EDT
[#14]
well just an update here.

PMC was happy to take the ammo back and they're sending me a FedEx label for that and the damaged case.

I guess I'll just keep pressing on.

Side topic:

Until this, I've never really thought about a squib on an MG.  What brand ammo do you all use for your MG's?  I like the PMC because it's not terribly expensive.  What else is there?

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2/5/2024 10:33:17 PM EDT
[#15]
Quote History
Originally Posted By peachy:
In my experience with open-bolt SMGs, I wouldn’t read too much into the case head being imprinted. That is just what happens in those platforms. Even weak 9mm ammo that will barely dribble out of my Uzi has far more pronounced stamping of the case head than that.

ETA: checked some .45 brass out of my M10, and it isn’t stamped. Maybe it is just an Uzi thing.
View Quote

That’s been my experience as well. It’s especially pronounced with the Uzi, but I’ve gotten it in the M11/9 sometimes as well. And not necessarily with hot ammo.
2/6/2024 5:32:02 PM EDT
[#16]
Quote History
Originally Posted By ggllggll:
well just an update here.

PMC was happy to take the ammo back and they're sending me a FedEx label for that and the damaged case.

I guess I'll just keep pressing on.

Side topic:

Until this, I've never really thought about a squib on an MG.  What brand ammo do you all use for your MG's?  I like the PMC because it's not terribly expensive.  What else is there?

View Quote



PMC is usually good. I reload almost everything that goes through my MG.
2/6/2024 7:02:06 PM EDT
[#17]
Quote History
Originally Posted By Deerhurst:



PMC is usually good. I reload almost everything that goes through my MG.
View Quote

Would you ever buy "remanufactured" ammo for a MG?  A FFL reloaded locally has 9. 45. And 556 at good prices, but I can't get over the reload factor.  Maybe it's me...
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Make your own Tac-Sling!
http://www.ar15.com/forums/topic.html?b=3&f=4&t=233665
2/6/2024 10:25:00 PM EDT
[#18]
Quote History
Originally Posted By ggllggll:

Would you ever buy "remanufactured" ammo for a MG?  A FFL reloaded locally has 9. 45. And 556 at good prices, but I can't get over the reload factor.  Maybe it's me...
View Quote



I would never buy "remanufactured" ammo. Don't care what it goes in.


The only guy with a Dillon I trust is me.
2/7/2024 12:01:38 AM EDT
[#19]
Quote History
Originally Posted By Deerhurst:



I would never buy "remanufactured" ammo. Don't care what it goes in.


The only guy with a Dillon I trust is me.
View Quote


I feel similarly. No problem with reloaded ammo so long as it is my reloaded ammo.
2/10/2024 12:32:43 PM EDT
[#20]
"The primer isn't just pierced, it's also flattened around the edges that should be rounded over'

Good eye...
3/23/2024 5:09:05 PM EDT
[#21]
Knowing PMC 9mm very possible the case was too long and the force of the bolt drove a good solid crimp on the neck resulting in a high pressure shot.

But I am new to these things.
3/23/2024 10:47:31 PM EDT
[#22]
What's going on with the mangled rim?
3/28/2024 12:01:16 PM EDT
[#23]
Quote History
Originally Posted By ggllggll:


Until this, I've never really thought about a squib on an MG.  What brand ammo do you all use for your MG's?  I like the PMC because it's not terribly expensive.  What else is there?

View Quote


On a Mac or UZI replacement barrels are cheap and easy.
I had a minty Colt 1921AC and the thought of a squib round terrified me. Replacement barrels are non-existent. There are pics of bulged barrels from squib rounds.
Fired it one time and put it away. Bought a "beater" WW2 gun to shoot. Replacement barrels are readily available for it.

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