They should work just fine . . . as long as your firing pin spring is not weak. CCI 34's are not as sensitive as the 250's as they're designed to prevent slam fires in auto guns. And the ignition will probably be a little different from the 250's, so you may need to make adjustment in your loads to get the same accuracy.Are these both similar? I have a 300wm and I’m running g low on CCI-250 LRMPs. I have a lot of CCI-34.