OK. Try taking the BCG apart. Any parts feel sticky or slow moving ? See how the firing pin is moving. Does it feel sticky,gritty or "slow" ? It should move/slide very easy on it's own. Might try using a lighter oil on those inside parts. Also might try running a pipe cleaner down the firing pin hole. Something gritty could have got in there. I wipe my firing pin down with a light coat of oil,but wipe it all off before re-assembly.