The SIG P220ST Is Cool; and now I understand the appeal of the 1911

[dsk]

It shouldn't have jammed like that. While most folks will recommend pulling the slide back to chamber a round, you should still be able to chamber using the slide stop in an emergency. Was the ammunition reloaded? .45ACP brass that's been reloaded too many times can actually end up with a slightly oversized rim. The result is a slight case of rimlock and a tendency of the round to nosedive during feeding.

 

[P. Plainsman]

No, it was factory ammo -- those Cor-Bon 185gr JHPs. I had previously chambered the first rounds in that magazine a few times (practice); otherwise they were new.

As many have noted, the P220ST has a rather stiff slide spring. On one hand, you would think that the strong spring and heavy slide would push forward with enough force to coax any recalcitrant round into the chamber. On the other hand, if the slide pushes forward too hard and fast, it might crash the round into the inside wall of the gun prematurely, before it has time to raise up out of the magazine and come up to the sloped feed ramp. It looked like that's what happened to my gun.

Sheer amateur speculation.