Blown primer...what next?

[TXBK]

Sounds ammo related to me. The IMI that I have shot seemed hot to me, and wasn't very accurate in my rifle. I know some have had success with it, but not me when I tried it. Purely unscientific observation on my part, but that's my impression of it.

[Clint]

Blown primers, even a single one are magnetically attracted to the fire control group. It's one of the laws of physics or something.

Yup, blown primers are bad juju.

That's why crimped primers are a real good idea and give some measure of insurance.

[markm]

The can pin Area sucks. If they get in there, the gun can be completely locked up.

[Eric D.]

Aren't the primers crimped on that IMI ammo? Most of their product line has crimped primers. It was my understanding a stray primer is a result of loose primer pockets whereas a popped/pierced primer is indicative of overpressure. One can experience stray primers without having pressure issues but I agree some of the IMI ammo seems fairly hot.

[tom12.7]

Primers pop out when there is less case support by the bolt face with the residual casing pressure blowing them out for their tension and a casing head distortion situations that reduce the proper tension between them. Higher peak pressures do not help this.
There's a few things that we can look at here, and a few remedies.

[markm]

Aren't the primers crimped on that IMI ammo?

Crimp depth and tension varies widely. I've had some xm193 brass where I could re-prime it without even removing the crimp. Whereas other types of brass/crimps can be really stout.

[tarkeg]

While that blown primer probably has an an ammo component to it, I would bet that Ned's reamer would fix it.

[nightchief]

I've ordered one of Ned Christiansen's 223/556 chamber gage to check the chamber. Will go from there depending on what I find out. Thanks to all on this thread for your info and shared knowledge.

NC

[odugrad]

Primers pop out when there is less case support by the bolt face with the residual casing pressure blowing them out for their tension and a casing head distortion situations that reduce the proper tension between them. Higher peak pressures do not help this.
There's a few things that we can look at here, and a few remedies.

If this was the case wouldn't this be happening all the time with different types of ammo?

[nightchief]

I tested the barrel with the Ned Christiansen gauge and I thought the chamber might be slightly on the tight side. I sent the barrel (entire upper) to the manufacturer for their inspection. The manufacturer felt the chamber was within spec. They also test fired it using IMI M193 that I supplied from the same lot, as well as Federal XM193 and had no failures either suppressed or unsuppressed. I have since checked another 11.5 " barrel chamber and the gauge was snug in that one also. I have had no issues with this barrel when running suppressed.

I fired approx 100 rounds of GECO 223, CBC M193 and CBC 62 gr 556 suppressed without issue. All of this ammo was fed from Gen 3 PMAGS. Perhaps one bad round is what I encountered. I will continue testing the upper suppressed and try out some CBC 556 77 gr OTM and BH 556 77 gr OTM or TMK and see how it performs.

As a side: Manufacturer was very good to work with on this issue. I had a good conversation with the owner (I think) about the testing they did. At this point, I guess I'll feel comfortable with the upper if I can get 1K+ through it suppressed without issue.

NC