Both M1 designs are *supposed to* mechanically retract the firing pin the last 1/8-inch or so of bolt movement forward, making a slam-fire impossible. The FP cannot extend to the firing position until the bolt is rotated at least 1/2 way into the locked position.
UNLESS parts are either worn or out of spec. Wear has happened with both USGI and commercial production units, out of spec AFAIK has only been with commercial production.
The parts to watch are the interface of the firing pin tang and the rear of the receiver bridge. A hint of a mark from the firing pin on a chambered round is normal, from the rattling back and forth the firing pin can do during the feed cycle.
Both designs CAN slam-fire with a combination of a high primer AND spherical powder in the load, which gets into the bottom of the primer pocket...that can be a fully open bolt ignition, most ugly.
Let's be careful out there, okay? Me, I've NEVER had a problem with five specimens of the various designs, and almost all rounds fired being reloads.