Posting this here cause the carbine bolt design is closer to the M1/M14 than others, I'm having light primer strikes with an Erma .30 carbine. It has a civilian receiver & barrel with all GI components. Went to range today, first ten or so shots were solid hits and functioned perfectly. Next five or so were every other, last five were non fires. First were deep hits, last were so light you could barely see them. Took it home, disassembled, firing pin moves freely, took fire control group apart, spring was strong (bitch getting it back in) and all movement was unrestricted. I'm using my reloads with CCI small rifle primers. Different types of brass. Is this a bolt or a primer seating problem?  I have another carbine, next time out I'll swap FCGs and see if that fixes it. Suggestions? Thanks

Could be excessive headspace?????

Good point. Why would it be intermittent? And what do you do if the head space is incorrect?

I would try some commercial made ammo in it first before getting too worried. You may have reloaded some out of spec ammo...........

Does the same with commercial ammo. Tried several types and my reloads were the best overall.

possibly you may have a compressed hammer spring from being left cocked for long periods at a time.

Make sure the bolt is fully going into battery.  Often, just the act of chambering a round will cause the firing pin to hit the primer and leave a mark.  Leading one to believe there is a light strike.
If the bolt doesn't fully go into battery, the hammer cannot properly hit the firing pin.  I would check the head space to make to see if it was too short or the chamber too tight.  If that is the case the round may not fully enter the chamber, and cannot rotate into locked position to the hammer can hit the firing pin.
I have a Winchester that I rebarreled which often causes that problem.  I recently checked the head space  and it is too short.  

Aah yes, good point!  Do you have a new op slide spring?  Or in other words the recoil spring?  Also, see if the op slide isn't binding someplace or rubbing on the stock when cycled.

Also, did you use grease at all?  Mine ran better with grease.  Not CLP or something like that.  I have to admit, I still can't get my carbines to run without choking once or twice in a range session.  I love that little carbine, but I would not trust my life to it.  My AR, M1A, Garand and 03A3 are much more reliable.