>The bolt of the M1 rifle can slam shut unexpectedly if the shooter has not strictly followed these instructions. If your thumb or finger is in its path, a painful condition called "M1 Thumb" is a strong possibility.
>In a half-century of military service with the United States and its foreign allies, the M1 has bitten thousands of recruits in this manner. No one ever died from it, but it did lead to a deplorable expansion of vocabulary in many languages.

With the greatest of respects, as any injury like that will produced unpleasant language...as noted by Ian at Forgotten Weapons, if you think the M1 will is bad, you've never been subjected to the M/42 Ljungman. The M1 bites...the M/42? Will try to EAT your thumb clean off of your hand. As I know from personal experience. Blue, black and with no nail.

...!
Gott's Leetle Feesh in Trousers!