What causes a bolt to come apart after being fired?

At the range yesterday with my friend, we had a M1 carbine bolt come apart after firing about 40 rounds. Prior to this happening, there had been no problems -- no misfires, failures to cycle, etc. By "bolt coming apart" I mean the extractor, extractor plunger and spring, ejector and spring all came off the bolt. Other than the bolt coming apart, we could find nothing wrong with the rifle.

My first guess is that the bolt coming apart is indicative of an overpressure problem, but I was wondering if wear on any of these parts or the firing pin could also cause this to happen?


Thanks in advance for you help.

Jim

Was the bold disassembled prior to firing for a cleaning? Was the bold reassembled correctly? Was the firing pin broken?

I've had a bolt come apart at the range because of a broken extractor plunger. Another common problem is an incorrectly assembled extractor/extractor plunger.

This is how it looks assembled correctly:
[IMGW]http://i28.tinypic.com/2upqtfk.jpg[/IMGW]

I have received carbines over the years that had soot so hard the plunger could not move all the way back. This causes the pointed end to get beat down and does not hold the extractor as will as it should. I got one with the plunger so beat up it was turned sideways about to come out. I have also received carbines with the plunger in backwards.
I also recevied one with a garand plunger and spring in it. At first I thought I had found a new design. What a laugh I had when I was told the part was for a Garand.

I would have to assume you didn't have a early type 1 plunger and extractor because these are rare and prone to failure.
So therefore I would guess that you had a damaged plunger or gummed up spring.
Jim C

Quote:

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Originally Posted by dukeofdata

I've had a bolt come apart at the range because of a broken extractor plunger. Another common problem is an incorrectly assembled extractor/extractor plunger.

This is how it looks assembled correctly:
[IMGW]http://i28.tinypic.com/2upqtfk.jpg[/IMGW]

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This. Most likely incorrectly assembled. And that is an incredible picture that's worth at least a thousand words.

"...if wear..." Yep. Moving parts do wear out.

Thanks to all for the comments and suggestions. We'll take a close look at the extractor plunger and other parts for wear, and make sure it assembled correctly when we put it back together.

Thanks again for your help.

Jim