I have been using federal small pistol mag primers for over 20 years in 38 special for my 2.7-3.0g target loads of red dot, bullseye, wst, etc. This is because I was also loading 357 mag loads and did not want to bother with 2 different primers. My Python did not always set off other brands of primers when shooting double action, the reason I went to Federal primers in the first place. Back in the early days of the internet. Some people say to drop back a couple or a few tenths of a grain of powder with a mag primer. I wouldn't know, I never use regular primers for .38.