I have a major 9 built on a Glock 22, KKM 40/9 barrel. I'm getting occasional failures to fire. Primers lightly dimpled, but no ignition. Tried several different primer brands (and yes all are fully seated). Primer brand doesn't seem to matter. I get FTFs with all of them. I swapped out the striker and striker spring with those from another Glock. The FTFs continued in the open gun and there were no malfs in the other gun. So it looks to me that the striker/spring can't be the reason. The chamber was reamed out by the builder when he built the gun. He did so because it was too tight and wouldn't seat my rounds all the way. The chamber liked some profiles, but not others. I questioned the smith about the possibility that the chamber may have been reamed a bit too much and thus cause head space issues. He says no, that the extractor holds the round against the breech face anyway.
I'm new to this and clueless so I'd appreciate hearing any and all theories.