I just picked up an ex-PD .40 4006. Great shape, $300.00 with 3 mags (11 round capacity each). I went to the range, no problems. Next time I went, however, I bought winchester round nose fmjs for target use. Virtually once every full mag, a spent cartridge woudl not eject; it would remain in the chamber, and the slide would drag another cartridge up to it, leading to a jam. Everything is cleaned and lubed, and I was wondering what coudl have caused this problem?