Misfire

[HeavyWrecker]

A while back, a friend was attempting to unload my Benelli M2. When the bolt came forward, the gun fired, without touching the trigger. The bolt then jammed shut. Hendersonville Police had great difficulty extracting the spent round. 
 

Has anyone else had a similar problem when there M2s?

[rahayay]

I was in a similar situation, but I can't help you with the solution. Waiting together for other replies(

[StrangerDanger]

I’d contact Benelli to see if they’d look at it if you can’t get the malfunction to reoccur by cycling the firearm. A 12 gauge snap cap would be the best thing to have on hand to test with. I’m not sure why it would jam the bolt unless something had broken off and bound up the action. 

[shootingsight]

Without knowing this gun, there are three reasons I can think of for this:

1.  The firing pin is jammed forward.  Either it is peened and jammed in the hole, or there is carbon or crud buildup in the hole.  Net, the protruding firing pin hot the primer as the bolt closed.

2.  Firing pin momentum.  Dunno if this gun has a firing pin return spring, but if the bolt closed fast enough, the momentum of the firing pin can carry it forward.  It's not unusual to see a small dimple in the primer on an M1 or an AR-15, because they do not have a return spring on the firing pin.  That said, it is rare to hear of a slam fire.

3.  Hammer follow.  For some reason, the sear did not catch the hammer when the bolt closed, so the hammer started to swing as the bolt was closing.

Whatever the cause, if it ignited the case prior to the bolt being closed, I imagine it could swell the base of the uncontained case, which is why extraction was difficult.