Lee: Make sure the firing pin tip isn't dragging in the bolt face hole. I've seen one with that problem and am aware of a couple more. Put some Dykem on the entire length of the pin tip, reassemble the pin assy. in the bolt and drop the firing pin using the trigger. Take the pin assy. out and see what kind of marks the Dykem shows.
Before you do this, you may want to manually decock the firing pin and check the pin protrusion a few times. Compare the protrusion amounts and make sure you're at least getting the same amount of protrusion each time. If it's inconsistent, that's a good indicator that the pin is wedging in the hole and not coming through cleanly. But, it can protrude the same amount and still be dragging.....just something to check.
The one I saw had a pretty good wedge going on. Surprisingly, it still fired and shot pretty well....tossing the occasional shot when the flags showed it should have plopped right into the group. Fixing the pin fit took the gun from Zero to Hero.
For what it's worth.......... -Al