Defender FTF

Had a glitch with my new Defender at the range yesterday. While shooting PMC 230 gr. fmj loads almost every time the last round out of the mag failed to feed. Actually it would go partially into the chamber with the bullet still visible. It did not matter whether the magazine began fully loaded or partially loaded. It was the stock 7 rounder that came with the gun. The only exception was the last magazine full which feed flawlessly. Those were Corbon 165 grn. hollowpoints. I am thinking magazine. What diagnosis do some of you have? Thanks.