Originally Posted by
tiger seven
I wouldn't exactly call them "undergassed" but LMT does drill their gas ports smaller than some other manufacturers. Grant and a few other dealers have clearly stated that this is due to them being designed to run on NATO-spec 5.56 ammo and not commercial stuff. But certain LMT uppers seem to handle SAAMI-spec ammo better than others, as I've seen some run okay on it and some choke horribly. I only have a statistical sample of about eight or so to base that on, though.
I will echo the previous comments and inquire what ammo was being used.
Derek