ID WW2 SMG or Auto breach bolt?

[Tom2]

Someone on an obscure website found this rusty bolt for a SMG or maybe auto rifle in the Alps in a cave apparently. He wants an ID of this. I don't recongnise it as being from a US gun but who knows. German SMG? Italian? any SMG collectors seen this?

 

[SDC]

Does he have any measurements of the bolt-face? Offhand, my guess would be a bolt out of a Revelli 1914 machine gun, which worked as sort of a weird gas-operated delayed-blowback, and the bolt-face would let us know if it would accept the 6.5x52 Italian round or not.

 

[Tom2]

Let me ask. He had a photo of the breach face and extractor but for some reason those pictures would not transfer to my pictures. Big claw extractor.