Am having some feed problems with a 10 round S&W short mag, Wants to short feed and not go fully to battery, Have 4 of the 25 round mags that function fine, just problems with the 10 round short mag that I bought primarily for sighting in on the bench where the longer mags just get in the way. Ammo does not eem to make any difference, operation is hit and muss and not a constant happening. Measure the mags from the retaining notch to the top of the lips and the 10 rounder is .012 taller, this should not really make any difference. Seems like too much drag on the top round from the bolt, it has to drag some or the mag would not feed at all. Possibly the mag spring is too stiff???