May as well check the auto sear release gap before you go out as well.
Again, just use the back end of two drill bits (one mic'd @ .080 and one mic'd @ .100) to check the release gap (placed the ejection port, and between the barrel extensionface and the carrier face). With the trigger held back and you riding the charging handle down, the hammer should be released off the sear with the.080 bit/gap, but not on the .100 bit/gap.
If the hammer is released with the carreir .100 or father off the barrel extension, then the problem is too advanced of a release timing, and not failure to lock up or bolt (carrier) bounce. With the added slowing cycle function of the MGI buffer, the carrier will be traveling even slower than norm, and the hammer is going to follow/strike the back of the carrier (firing pin still blocked) before the action has even begun to lock up (read hammer down on a unfired round in the chamber).