Putting together a M3K for 3 gun this year. Put a +6 Nordic extension on it, trimmed the follower spring a couple times, down to 12" longer right. If I put 10 rounds in the tube, the shell latch won't pull back after pushing the release button by the trigger. it moves a little bit, but not far enough to release the shell. I did trim the latch down on the shell side and polish it for easier loading, but didn't shorten it or change the angle. Sometimes you rack the bolt and it will release a shell, sometimes not. Works fine up to around 7-8 rounds, but not after that. Any ideas?