.22LR (AR-22) fired out of battery...maybe

My AR-22 build has run beautifully in the past. When seriously target shooting I use CCI product 0031 (standard velocity 40 gr lead round nosed). Yesterday I was plinking at steel with Rem Golden Bullets, infamous as they are.

The CMMG bolt assembly has its own recoil spring, so I reasoned that I could lighten the rig by removing the spring and buffer from the butt and replacing it with an exact-length tube of PVC for the rear of the bolt assembly to snug up to.

I can't see how that change could create what occurred, but I have put the original spring/buffer back in.

What happened was, I was experiencing fail to feed, some fails to fire, and then bang and a sting on my forehead. Removing the magazine and opening the bolt and getting the skewed cartridge out of the way, an entire rim head fell to the bench.

The rest of the fired case remained in the chamber. I pushed it out easily with a cleaning rod. I could see bits of lead in the action, and figured I had survived an out of battery discharge without injury. Even the stinging forehead spot left no mark.

When I got home and took everything apart, I found part of a brass case caught under the extractor, which explained one fail to extract that had happened on the range. The end of the extractor claw looked like it had two pieces gone, leaving a very small point to grab the rim. New one coming.

A call to tech produced the assessment of an overcharged round and burr(s) that need to be polished away. In 71 years of gun-related experience and reading, this is the first I have heard of overcharged .22s. I think debris held the rim away from the chamber face and nothing was supporting the rim....meaning there is an inadequate out of battery safety. That or a slam-fire found the right condition to happen. Bolt was clean as was the firing pin, which has a spring that the hammer overcomes.

I had complained to tech that on feed, the top of the ogive gets a notch in it, and the bottom of the bullet receives a heavy gouge to the beginning of the drive band, pretty obvious the bullet is being wedged at an angle as it enters the chamber. The lead shavings accumulate until they become a problem. That brought the suggestion that there are very small burrs at work.

I polished the feed ramp (without measurable removing of metal). A chamber polishing had been suggested. The chamber is a mirror and this rifle had been running fine before this day. I wanted to address the areas that are mutilating the bullet, which I had been aware of from the git-go.

In my vast selection of scraps was a wooden dowel .313" in diameter. I rounded off one end, charged it with a gritty tooth paste, chucked it in a drill, and polished the slight chamfer of the chamber, widening it a couple tenths.

I removed about .005" from the extractor where it rests against the bolt body, allowing the claw to engage the rim a little better while waiting for the replacement.

I fired CCI standard velocities, six in a rapid row, running as it should. I don't know yet if I have managed to reduce the bullet mutilation. Seems that should affect accuracy. That all remains to be seen.

All this has me thinking about acquiring a Ruger 10/22.

As much as your tinkering, just build one they way youd like it on a virgin 10/22 reciever.
Could make a pretty decent 10/22 pistol..

the broken extractor and brass under the claw sounds like it acted as a firing pin on the rim when the round went up the ramp to the chamber. I have the very same setup and I'll keep an eye on that bolt face
good write up!

Wow! Didn't think of that. Thanks.

I have the pieces. The head is perfectly intact, and the firing pin strike looks normal but looks like a light strike...another reason to suspect out of battery ignition. Not sure about the extractor...don't know what it looked like before the incident. It kind of comes to a point, and each side of what becomes the "point" seems rough, suggesting damage. Just doesn't look right. It barely grabbed a rim so I deepened the engagement a little.

The head/rim is about .045". The shell that was left in the chamber is very cleanly broken off and is .459" in length. An unfired case measures .594, so .090" of case is missing. There is a small section hanging off the rim that is part of that missing section. That seems to indicate the cartridge was .090" out of battery.

An AR15 bolt disengaged that much would not allow ignition due to lug rotation. I don't see where this none-rotating setup has any built-in out of battery safety.

I have 5 CMMG Bravos set up in dedicated uppers. Two are set up for full auto. Rem Golden Bullets will not even reliably chamber in any of these set ups. I use Federal Auto Match and it runs very well in all of the uppers. FWIW.

Bob
d

Theres really no oob protection on the 22 conversion kits. I will say I have had extractors that were too stiff or stuck ignite 22lr before. Both on my 22 conversion and ruger 10/22

Would the case have to go to seated in order for the extractor to dent the head? Or could it happen when the bullet is riding the ramp? In that case, the blow-out would be chaotic. Could you tell?

Just got back from the range. 100 rounds of Federal 40gr RN ran like a top. Checked a couple of chambered rounds, no feed gouges at all. Happy as a clam. Whatever the derivation of that comparison. :D

And today, I bought a new 10/22 carbine. A 10/22 on 10/22. Not planned. A new adventure begins.