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Posted: 7/30/2007 1:16:51 PM EDT
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Took my AR to the range the other day. My rifle was a little dirty but clean enough to shoot a couple hundred rounds, so I just gave it a little clp to make it through the day. I fire 10 rounds and the 11th just goes click. I take the upper off and half of the bolt is stuck in the chamber with a live round in front of it. I waited a while for it to cool off and I pulled it out no problem. The AR is one that I put together a couple years ago. The bolt came with a complete upper I bought from from J&T Distributing. The rifle has been fired about 3,000 times. I had not noticed any cracks on the bolt before it broke. I know that bolts will eventually fail in some way but I thought it would take alot more than 3,000 rounds to do it. So, what happend? Did I just get a lemon?  Sorry for the quality of the photo. |
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I guess that this bolt was not properly heat treated & or inspected properly. An MPI inspected bolt should last many times that round count. Then again, a bit of lube now and again, and less stress when unlocking would also extend the bolt life. What I mean when I say less stress, is that the ammunition's pressure curve should be balanced to the gas port size and location allowing the system to function with minimal stress. |
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It's a defective bolt from the start (as pointed out above), and if you give J&T a call (since this is where it came from), they will send you a replacement. As for something like this (heat treated too deep/brittle), chances are a MPI would not show any problems, since the problem is a too brittle problem, and not a crack problem when it was manufactured. en.wikipedia.org/wiki/Magnetic-particle_inspection |
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