Blown primers

[mississaugagunnut]

I wanted to relate an issue I had with my rifle at Earl Green's carbine course last week.
The rifle was a Dpms upper on an Armalite lower using Norc ammo.
Near the end of the second day I had 2 malfunctions where a primer fell into the area where the bolt locks up. This prevented the bolt from going completely into battery.
Some people at the course felt it was the ammo to blame saying it was too hot. I have fired almost 1000 rds of this stuff and never had this occur before.
I have a different theory.
During the second day, around lunch time I sprayed a liberal amount of Ballistol on the bolt and carrier. For much of the course we had our rifles slung muzzle down. See where I am going?
I think a bit of slug and Ballistol got into the bore and when a round was fired this caused an over pressure condition which pushed the primer out.
I cleaned the rifle thoroughly at home and took it to the range this week. I fired 100 rds of Norc in a rapid manner with no malfunctions.
What do you think?

 

[Runningfool]

That is strange...hard to imagine Ballistol building up in the chamber to cause over pressures high enough to pop primers though. I take it you were shooting the norc 223 ammo?

We're the primers punctured/perforated?

 

[Conte]

That doesn't make sense to me. During the combustion cycle, when there is enough pressure to to pop out the primer, the case head is being supported by the bolt, so the primer is being held in place.

Truth be told, that's all that stops the primer from getting popped out as the normal pressures are enough to pop it out. In most cases, your primer actually does get pushed out a bit, then either sucked back in by back pressure, or push back in as the case expands against the bolt.

If there was enough clearance for the primer to slip past the bolt, then that would also mean the bolt is not engaged onto head and you would likely not get extraction. It also means your bolt is not locked into battery at that moment, in which case, you'd loose the entire case head not just the primer.

I think I'm just rambling now. Anyway, I could be wrong, but your theory does not seem possible.
I have heard mention of this phenomenon before, I forget what caused it.

 

[fred0000]

FWIW I've had primers fall out of norinco .223 brass after 1 firing, not in my firearm, but they were falling out at my bench.
2-3 just fell out on their own, but ALL of norinco brass I have come accross has loose primer pockets

 

[notsorichguy]

I have run 4K+ of nork ammo through several firearms.

When temps hit +20, I will loose 1 in 10 primers....... When temps are near freezing (+5 or lower) not a problem......

Me thinks that nork ammo is not temp resistant......