M1A intermitent FTF

I shoot my M1A in our clubs Military matches and at the last couple of matches I have been experiencing numerous failure to fire problems. I always run the rifle with the gas turned off and cycle it by hand with the bolt(so I don't have to chase brass). At least one out of every ten shots the round does not go off. Sometimes there is no firing pin dent in the primer at all and sometimes it is light. I have done the tilt test and the bolt goes into full lockup with no problem. I have dry fired it while watching the bolt and it does not turn at all while in lockup. It never missfires twice in a row. The firing pin looks okay(I don't have a protusion gauge so I'm making a guess)and the rifle is kept well lubed. When I cycle the trigger group while it's out of the rifle it works fine every time. The hammer doesn't seem to have any undue wear except for the little spur that goes into the back of the bolt. I have not disassembled the bolt, could the problem be in the bolt? Is it possible that there is too much grease ending up on the back of the bolt causing a sort of hydraulic problem? Any ideas would be appreciated, Thanks.

Check the length of the hammer spring

It's 2.26". The spec is 2.15", if it's longer than this is it considered out of spec?

My crystal ball sez.....if you are cycling the action by hand the bolt may not be fully locked and the bridge is preventing the firing pin from striking the cartridge fully. Does the rifle operate OK when the spindle valve is turned to the on position?

Other things to look at:

• Ammo defective
• Firing pin protrusion insufficient
• Firing pin stuck (clean the inside) or broken
• Hammer spring weak, altered, broken, or wrong (change it)

The ammo is my handloads that I use in my other four .308 rifles, it seems to work fine in them. The firing pin moves freely in the bolt. I will turn the gas on and see if it's the hand cycling that is the problem.

Did you check the headspace ? I always used the same handload in the same rifle. Your handloads could have a shorter length in this rifle which might cause the firing pin problems ?

I will check that also, I feel kind of dumb for not checking that first.