Pierced primers

On the M1 and M14/M1A the firing pin is retained in the bolt by the extractor. The hammer stays against the firing pin upon release, until bolt unlocks and drives the hammer to rear recocking it. The M4/M16 is similar. In the universal receiver, the firing pin is only about .500" long, and the hammer is rebounding, it hits the pin and bounces back. There are differnt sized firing pins and firing pin plates, depending on the caliber. We also adjust firing pin protrusion (FPP) and firing pin indent (FPI) for caliber. Example; 7.62x51(.308Win) FPP is .060" to .068" and FPI is .020" to .025". The FPI is measured with a copper cylinder, and insures that there is enough energy to set off the primer.
 
M1Gunsmith, you started with the floating firing pin and no pierced primers. Now you have moved to the bouncing hammer. I have hammers that do not bounce when dropped on an empty chamber, I do have hammers that bounce when dropped on a loaded chamber.

F. Guffey
 
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