Buffer failure at match today

I thought some of you AR owners or SOTAR grads would appreciate this. One of the competitors at the match was just about finished his string when he had a failure to eject. He tried the mortar technique but couldn’t get the bolt to move back more that a few mm. Time expired and he lost points on that stage.

He was able to move the bolt back and forth only about 1/4” so he locked the bolt, removed the lower and retracted the bolt easily. The case ejected without any resistance. He reassembled the gun and thought he was back in business. However when getting ready for the final round he couldn’t pull the charging handle back, so he left the line and took a zero on the final stage. I was keeping score and offered to check it out once the relay was over.

While checking the upper and BCG I couldn’t find any signs of damage or wear. The bcg slid and locked freely. Then we checked the buffer by trying to depress it with thumb. It wouldn’t budge. Eventually we were able to depress it but there was a lot of resistance. Once we removed the buffer we found the problem.



The bumper was missing from the buffer and roll pin was gone too. I has assumed it had fallen off and was stuck inside of the buffer tube. However when I tapped on the stock the pin fell out, along with a pile of little pieces of crumbled plastic.



The owner was a serious competitor that said he had over 10,000 rounds through the gun. So the buffer was original. He noted that he replaced the original buffer spring with a titanium spring about 2500 rounds ago, and hadn’t noticed any problems with the buffer.

I’m guessing the bumper had failed quite some time before today’s match. I’m guessing it was just pushed to the back of tube and was broken apart and continually crushed with each buffer impact. The black particles stuck to the spring and weights appears to be pulverized plastic.

I suspect the roll pin worked loose and the weights fell out of the buffer and stacked up inside of the spring at some odd angles keeping the buffer from moving back.

So buffers can fail eventually.

EDIT: Just thought I should add this was a Colt HBAR Rifle.

That's badness.

Hummm... that's a new one on me. Thanks for posting.

That will not buff right out.

Never seen that before. Thanks for posting it.


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This is what happens to a severely over-gassed gun sometimes. Buffer cushion gets beat all to hell and all sh!t hits the fan. Also, you need to occasionally pull the buffer for inspection and make sure the roll pin is flush on both sides of the buffer, otherwise it will eat the spring at the same time the spring will eat the roll pin.

Good stuff. Thanks for sharing.

Wow, never seen that before. Something else for me to check when I do my periodic firearms inspections. Thanks for showing this.

Next time, extra strength:

Must admit, that's something I never check. Thanks for posting.

Great information! Thanks!

That’s crazy. I’ve never seen anything like that happen in an AR.

I have experienced such a meltdown with a relatively new buffer. 300AAC, SLR block set wide open for subsonics unsuppressed. Next range trip, I started out with supersonics, suppressed. Way too much gas! It was back when I was working up loads for my new gun. I learned an important lesson. At the beginning of each range session, I verify the setting on my gas block.

Good info, thanks.

Thanks for posting ToolAA.

I wonder if his gas key was hitting the lower receiver after the buffer began to fail.

Did he mention what lubricant he was using? Wonder if it attacked the rubber buffer pad.

clandestine said:

Thanks for posting ToolAA.

I wonder if his gas key was hitting the lower receiver after the buffer began to fail.

Did he mention what lubricant he was using? Wonder if it attacked the rubber buffer pad.

Click to expand...

I inspected the BCG closely when we first removed it and I didn’t see any unusual wear or marks. If the gas key was hitting it would be making contact with the thread ring where the buffer tube attaches? If so that looked normal too.

As for lube his rifle looked fairly dry. I could only see a very light film of lube on the BCG. No grease, looked pretty clean actually. The guy was ex air force and had been competing for at least 20 yrs, including matches at camp Perry, so I’m guessing he was used to typical military cleaning habits.

I’m wondering about the titanium spring? That’s what he said he swapped out. I searched for titanium springs and I couldn’t find anything online. Have you ever heard of titanium buffer springs?


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Ditto on the thanks for sharing.

OEM Colt buffer? Not that I'm ascribing it to a manufacturing defect, but realizing that it can be a point for wear/failure for any buffer then. Perhaps the spring was an imperfect fit as well and somehow rubbing on the buffer caused the wear. That or some foreign material made it in the tube when he replaced the spring (or even a small bit of the spring broke off) and was damaging the buffer on repeated cycles.

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Looks like I'd better learn my AR better before I hit 10k rounds

This kind of post is what makes this forum so valuable. Thanks for the heads up.