Put together a Cobra40 and it would not fire at all, tried 2 different 40sw ammo brands and nothing every time. Tried the ammo in friend’s glock 22 and it ran well, so I took apart the slide on the sd40 to check the firing pin and saw the spring was in 2 pieces and was 2 different colors. I’ve never taken the slide apart since its worked before on a separate build. I replaced the spring with an aftermarket glock competition spring and it seems to be compatible. Ill report back whether or not this was the fix but I assume it’ll fire now