To much crimp can bulge the case shoulder or neck on any cartridge. On an AR the round may chamber fully, but be hard to extract if not fired. There is no crimp needed with proper neck tension. Measure the neck before & after seating a bullet. Has the bullet expanded the neck by at least .002" This will give about 35 lbs minimum neck tension. Test by using a dummy round, place on bath room scale. Use leverage to slowly apply pressure to the bullet, till it pushes into the case. Watch the scale.