NSN 5220003456122 is, in accordance with the related link parts logistics, is a "GAGE,FIRING PIN PROTRUSION".
You need to get assistance from a qualified gunsmith.
go 0.064" no-go 0.071" Also, check firing pin protrusion from bolt face.
Yes the firing pin should float freely on top of the breech bolt. If you take the gun down (seperate the receiver) the firing pin will be visible, and should slide freely backa and forth.
Find a good gunsmith or machinist
This issue can often be caused by worn firing pin springs or fouling within the firing pin channel. A common fix is to disassemble the bolt, clean the firing pin channel, and replace the firing pin spring if necessary. You may also want to check for any damage or wear on the firing pin itself.
A firing pin that is mounted on/in a hammer
Firing Pin Block
Firing pin is held in the falling block by a retaining pin. This is not normally removed or replaced for routine maintenance. Rather than provide instructions, I will suggest that this go to a gunsmith, who should also inspect the firearm for safe condition prior to installing the firing pin.
Like it says, the firing pin rotates as the action cycles.
By action of the hammer striking the firing pin, forcing it into the primer.
Firing pin is what strikes the back end of bullet igniting propellant