Primer strike from chambering

[Ranger86]

Good afternoon,

I just chambered a round on my primary AR and then ejected it without firing. When I went to load it back into the mag, I noticed the primer was dented. Did this again with a different round getting the same result.

The rifle is a BCM lower with giessle SSA trigger group. Upper is a Sig 516 piston AR.

I have thousands of rounds through this rifle and took it through a 2 day, 1000 round class without issue.
Just so it is said, never an AD from chambering.

This cannot be normal, right. The firing pin is not proud of the bolt face unless pushed forward. Rifle is clean and lubed. What mechanism stops the firing pin from moving forward and hitting the primer as the bolt slams home?

Any troubleshooting advice would be welcome.

Mike

Sent from my SM-G960U using Tapatalk

[Kadelic]

Completely normal. The momentum of the bolt moving forward to chamber a round causes the firing pin to "kiss" the primer enough to leave a mark.

[1168]

Normal, bro.

[Ranger86]

Thank you, i was thinking WTF. I guess I never looked at the primer on a round I chambered but didn't fire.

Again, thank you.

Mike

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[El Vaquero]

As others have said, it’s normal. There are several articles floating around the interwebs that say not to repeatedly chamber the same round as it can damage the primer. I do see how that can happen but have not personally heard of any negative experiences. Could be truth, could be rumor or combo of both.

If it’s your duty or home defense rifle for me it’s not worth the worry. That round is now officially a range round. Does not go back for duty service.

[1168]

As others have said, it’s normal. There are several articles floating around the interwebs that say not to repeatedly chamber the same round as it can damage the primer. I do see how that can happen but have not personally heard of any negative experiences. Could be truth, could be rumor or combo of both.

If it’s your duty or home defense rifle for me it’s not worth the worry. That round is now officially a range round. Does not go back for duty service.

Doc GKR said something about commonly seeing failures to fire on police ranges due to this. I’ve personally never seen one I could attribute to this, though. Despite participating in the .mil practice of clearing and chambering repeatedly. But, I do have an ammo can labeled “random garbage .223/5.56” that these go into, just in case. They get gobbled up on the range.

[Chubbs103]

Perfectly normal. Because of this, I believe caution should be exercised when reloading for any rifle with a floating firing pin. There is a reason they make primers with a harder cup for military rifles.

[ST911]

Doc GKR said something about commonly seeing failures to fire on police ranges due to this. I’ve personally never seen one I could attribute to this, though. Despite participating in the .mil practice of clearing and chambering repeatedly. But, I do have an ammo can labeled “random garbage .223/5.56” that these go into, just in case. They get gobbled up on the range.

No news to you but for the benefit of others- It occurs, short version is FP contact with the primer with repetitive chambering can damage the priming compound. Less common than it used to be as the word gets out and better practices prevail, and better primers too. It's always possible, but not always probable. Like you I'm sure, I've seen a lot of trashed ammo with multiple chamberings feed and fire without issue.

[Uni-Vibe]

I use only CCI #41 primers, even though they cost more. They have a harder cup for the AR-15.

[mlberry]

That's also one reason you shouldn't put a round in the chamber and then hit the bolt release letting the bolt slam home. It's best to let the round feed from the magazine or ease the bolt into battery and actually use the forward assist to make sure it is locked. The M1 and M14 rifles had the same problem as they also have free floating firing pins.