Hopefully someone has some advice. I have a SWD/Cobray MAC-10 A1A Full Auto I bought new. In great shape using new Zytel 32rd Mags and new 115gr 9MM ammo from Federal or other bulk manufacturer. After full cleaning, still cannot go more than 8-10 rounds before jamming. The spend case will not extract fully before the bolt returns forward and jams. Any ideas ? Is the ammo too weak to reliably cycle the rounds ? Are the bolt springs too strong ? While not the most advanced SMG, I should be able to get more than a few rounds through it. Any help / advice is most appreciated.