Free: Contests & Raffles.
I assumed you are talking a handgun? I'm not sure some of the differences in caliber matter that much (357,40,41,44,45,10mm etc). The noise maker part is second only to your awareness. IF you were to really need it to stop a bear where bullet size and velocity matter, you're probably hozed anyway.I wouldn't over think it. You do the best you can and march on with life. People need to be prepared but they WAY over worry about bear attacks IMO.