[HookedOnTheOutdoors]

I tested the following and found that there is little difference in velocity between a Winchester small pistol primer and small pistol magnum primers from CCI, Federal and Winchester:

Factory Ammo - Remington UMC 125 gr JHP Average 1353

Winchester Small Pistol -- 7.2 gr -- Average 1321 fps
CCI Small Pistol Mag -- 7.2 gr -- Average 1333 fps
Winchester Small Pistol Mag --7.2 gr -- Average 1325 fps
Federal Small Pistol Mag -- 7.2 gr -- Average 1351 fps

Winchester Small Pistol -- 7.6 gr -- Average 1357 fps
CCI Small Pistol Mag -- 7.6 gr -- Average 1376 fps
Winchester Small Pistol Mag --7.6 gr -- Average 1388 fps
Federal Small Pistol Mag -- 7.6 gr -- Average 1391 fps

Winchester Small Pistol -- 7.9 gr -- Average 1395 fps
CCI Small Pistol Mag -- 7.9 gr -- Average 1406 fps
Winchester Small Pistol Mag --7.9 gr --Average 1383 fps
Federal Small Pistol Mag -- 7.9 gr -- Average 1407 fps

I didn't notice any flattened primers. Haven't measured the cases yet.