I love how this forum flows. He stated that the charging handle would lock-up and he had to "mortar" the gun to clear the jam.
ONE guy mentions switching magazines which is NOT the problem at all, then everybody goes on to talk about magazines, ignoring the original problem posted.
A feeding device will not cause the gun to lock-up so badly that the rifle needs to be "mortared" to clear the chamber
Its most likely the ammo.
RC