I found some #41's on Gunbroker a few weeks back for 8¢ per and will use them in my .30 Carbine. I don't think they could possibly be as hard as some of the Russian primers I've used! Truth be known, I use any primer that will fit the primer pocket of my .30 Carbine's. Yes, even small pistol and small pistol magnum. FWIW, I've chronographed this cartridge with all four different types of primers (SR, SRM, SP, SPM) and a variety of loads and found not enough difference in velocity to matter.
35W