You are going to have much fun with that Python. The cartridge picture you published doesn't show much roll crimp. There is no cannelure, so perhaps they are taper crimped. I don't know as have no experience with this ammo - maybe someone else does. Lots of talk about crimp here and I don't know if anyone mentioned this yet, I apologize if they did, but every reloader needs a good dial caliper. Not a digital, but a dial caliper. If cases are all exactly the same length you will have best crimping results. The little Lee hand trimmers work well for pistol cases when you need to trim. Happy shooting!