Stuck M2 firing pin nut...
Just about done detailin' my new M2. Bolt is cleaned up and ready for reassembly. Tried to take the firing pin nut off last night. Would not budge. Sprayed it down with oil. Tried again tonight, no go. The assembly is in good shape, no rust. The entire bolt assembly was packed with cosmoline. So on the way home from work this evening stopped off at Ace and bought a can of Brakleen. Sprayed the cosmo off, let the assembly dry and then sprayed everything with Remoil.
Have a copy of the ordnance manual and followed the instructions, but again the nut would not budge. Not gonna' obsess over this, as the bolt functions perfectly. Pulled a bullet from a .22 long rifle cartridge then put it in the chamber and eased the bolt over it. Pulled the trigger and the primer fired. Firing pin made a nice round dink right where it should be. It ain't broke, so I ain't gonna' fix it. This does bring up a question though. The nut has a prominent knurl and the face has detents that a tiny spring fits into. Figure this design was intended to compensate for variances in the hardness of the rims of commercial .22 ammo that was used back in the day. Dial the pin forward or backwards to get sure fire depending on the ammo that you are using. I can't see any other reason for the nut being designed the way it is. Gonna' grease the spring, reassemble the bolt and call it good. Any input from M2 experts would be appreciated.
Death to stuck nuts,
In all my research and talking to experts on the M2 Springfield I have never read or heard any mention that the firing pin nut was adjustable to compensate for variances in ammo. The little detents are to hold it from backing off. I too have encountered stuck firing pin nuts. I suggest letting it soak in penetrating oil then holding the parts firmly with some type soft metal contacting the parts then using force to turn it.
I've also had trouble with a firing pin nut and after soaking, I was able to turn it off using one of those rubber disks that are used to remove stuck jar caps.
Sometimes by mind has nothing to do but think up things. Adjustable firing pin would just cause trouble. The nut stays for now. I should be shootin' in about an hour.