Do a direct thread and can swap on any caliber size as can or smaller. I use a 30 can on 300wm, 308, 243, 6.5cm, 6cm, .556, etc. I have also used a 338 can on a 556. I have even used a 30 can on a 22. But you can't shoot a 44 mag out of a 30 cal can. The bullet is bigger than the can opening!!!