It's not the length of the barrel that matters, it's the dimensions of the chamber and the inevitable variance between examples due to manufacturing tolerances. FWIW, my Scorpion Carbine ate everything I ever tried to put through it, even rounds that my CZ pistols rejected. That said, I didn't shoot much JHP through the Scorpion, but I did shoot a wide variety of coated lead bullets(.356 & .357) before I sold it. Probably the least ammo picky gun I've ever owned. Everything that didn't pass the gauge/pistol chamber check went into a pile for the Scorpion.