According to the Armourer's Handbook, the firing pin protrusion sould be about .045" . .050" being the max and .040" being the minimum. A
wartime measure allowed .055", but .050" is as much as you should need for commercial ammo.
Take the bolt out of your rifle. The tip of the pin should NOT be protruding from the bolt face.
Unscrew the bolt head about 1 turn and then back in. It should make contact with the firing pin and push it back slightly. The bolt head should not turn past the long rib on the bolt more than 15 degrees.
Turn the cocking piece counter-clockwise(like it would be turning when you close the bolt). This will let the cocking into the long cam groove on the bolt, you can then measure the protrusion of the firing pin.
If the pin is too long, then remedy is to adjust or replace it. If it's too short(not likely here) it should be replaced.
Springfield sporters at
http://ssporters.com should have the parts. Sarco had firing pin tools.
Arrowmark tools in Australia has gauges and tools
http://www.arrowmark.com.au/
I have shot several boxes of PMP in .303 and had no problems with it. It is made by the same factory that made all that 7.7x56 mil-surp in the 50 round boxes. The only differance I can find is that PMP commercial uses Boxer primners and is thus re-loadable.