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Broken AR-15 bolt

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I've been shooting M16s and AR15s since 1975 and have broken 8 bolts in my lifetime. I've always broken them in ARs with CAR length gas systems, never in a midlength or rifle length AR. Sometimes the break at the cam pin hole sometimes they'll shed lugs.

One last post on this. I was able to speak with Bill Alexander of Alexander Arms where I got the compelete upper. I sent them the broken bolt, he examined it and said there were not any signs of it being from a pressure problem. They're sending me a free replacement, and I ordered a backup too, just in case! He also told me that the bolt was a previous model and that the one's I'd get are their latest model, and that they'd be offering an extreme duty bolt for a higher price soon.

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Adam B   
The LW bolt is the best on the market...bar none

Bolt breakage is more common than you might think.


Jim do you have these in stock? I have 2 on backorder with Brownells and would like to get them before 2010

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I've learned a lot from this thread. Guess I better start carrying a spare bolt in my bag-o-tricks. Thanks for all the great info!

Here is even a little more info, I thought it only fair to show what Bill Alexander replied in the 65grendel.com forum:

" Let me clarify this completely so that there are no misunderstandings.

- The bolt in question had a machining error present. In manufacture one of the cutters had broken and the operator had replaced it with a regular end mill rather than a radiused cutter. This resulted in a sharp edge which acted as a pre machined crack. We beleived that we had caught all these items but this one had escaped.

- The loads with the 140 grain SMK are probably at absolute maximum for the working pressure but I cannot verify this without testing. The very short ogive and long bearing surface will drive pressures. Regardless the gun should have operated without this problem as there should be a significant safety factor but the maching error removed this.

- The bolt was replaced with our current production unit. Since the inception of the Grendel I have made several small adjustments to the design to to add to the safety factors and aid inspection of the critical areas.

- The new carrier assembly is part of an ongoing project to upgrade the cyclic life and reliability of the upper reciever in adverse conditions and when subjected to very high round counts, in response to requests from some of our customers. The design is to increase the fatigue life of the unit not to allow for heavier than standard loads.

Bill Alexander "

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The military specs that all bolts be magnafluxed (MP) to look for stress fractures. Alot of companies do not do this and these bolts tend to break more often. Bolts from Colt, LMT and Bravo Company are all MP tested and shot peened and are more durable. Not saying these won't break but it is alot rarer. I got one of the LW bolts and to me it's worth the money.

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