Traditional SD ammo is not always tested in 3 inch barrels and many do not reach full velocity needed to properly expand. Several companies make ammo designed for short barrels, faster burning powder. Just cause it cycles in your gun does not mean it's effective SD ammo. Gold Dots for instance do not expand from a short barrel, despite being a favorite of many, including me out of a 5 inch barrel. I use Remington designed for 3 inch. barrels. I think it's called micro?