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Discussion Starter · #1 ·
Ok, let me explain... I know what headspace and timing is - everyone who has worked with a M2HB knows that... What I am wondering is if 16 series weapons have the same thing when you replace the barrel. A buddy took his M4, I believe it is a tactical weapons brand or some such, and the bolt simply came apart after about 15 rounds during zeroing (firing slowly). It was the first outing sense he placed a new barrel down on it - which he torqued to specifications.
 
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Discussion Starter · #3 ·
No, it split where the cam pin goes inside of the bolt itself. it split up and down as the bolt sits in the bolt carrier with the weapon upright in the firing position.
 
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Discussion Starter · #4 ·
From what I understand, all rifles and semi-auto pistols have a head space that needs to be set either at the factory or by a smith (an ambitious do-it-yourselfer could probably do it too) in order for the round to be seated properly. Too little head space and the bolt will impact the casing too hard and may cause damage to the weapon in extreme cases. Too much head space and the round may not fire or the bolt may not lock properly.

I'm guessing that your friend did not check the head space after installing the barrel and it was too tight. Repeated slamming of the bolt probably caused the fracture.

Or the bolt was defective to start with.

Pictures of the broken part would help though.
 
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Discussion Starter · #5 ·
Yeah I am going to get some from him, I just had a brain fart after we fired on the range and didn't take any. I took plenty (actually my significant other did - thank goodness she loves to shoot but doesn't have a well developed trigger finger muscle :D ).
 
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