You don't specify what gun, or your intended use, so that leaves it kind of up in air. I loaded .38-55 WCF years ago for single-shot (Ballard, Winchester High-Wall) rifles for 100- and 200-yard target shooting. Lead bullets from 255 to 330grains weight, with appropriate charges of IMR 4227 powder achieved accuracy near 1MOA regularly. This was always considered one the top cartridges for accuracy at longer ranges in it's heyday of 1890's to 1920.