I happend to see my brother-in-law's ammo on Easter. Had HMR and M2 ammo for his rifle chambered for HMR. I told him not to fire the M2 in the HMR rifle. It turns out he already fired some rounds and they did fire. I told him to stop immediately. The stupider-than-my-brother-in-law guy at the gun store did not know the difference between M2 and HMR. "Hey it's .17 right? What's the difference". What could happen if he shoots the M2 in the HMR? He's as dumb as a box of rocks sometimes but I still like the guy.