Trying to keep things simple. 38 Super small pistol-rifle primer chronograph comparisons Sierra V load data uses WSR (small rifle) primers rather than small pistol primers, 8.1grs WSF is their max powder weight. Colt Govt, 4300ft, 79F to 84F, 65% RH WSF/7.5grs, R-P +P unfired brass, COAL 1.234 +/- .001, 121 Zero JHP, true .356cal bullet for the .38 Super CCI 500; 1464fps/576fpe, ES 48fps, SD 17 WSP 1434fps/567fpe, ES 24fps, SD 09fps Federal 100 1438fps/556fpe, ES 12fps, SD 05fps Small rifle primers WSR 1435fps/568fpe, ES 41fps, SD 16fps CCI 400 1495fps/600fpe, ES 105fps, SD 37fps Remington 7 ½ bench rest 1458fps/571fpe, ES 69fps, SD 21fps I have don't have an explanation why the CCI small rifle primer gave such horrendous extreme spread velocities. Both WSP/WSR primers gave the same MV, but the WSP had a lower ES. In contrast, the Federal 100 primer load (lowest ES/SD numbers) gave this small group of ejected brass at about 5 feet; For those who load for competition, WSF could be backed off a bit and still make major. This is a loud powder. Bob Wanna kill these ads? We can help!