I started reloading ammo in 1953. Over the years bullets have become game weight specific and also to handle the higher bullet velocities from mag rifles. When I first get a different rifle I find an accurate reload for it and then purchase additional components to last me for some time. My main big game rifles are a 270 Win, 308 Norma Mag, and 340 Weatherby Mag. Before going big game hunting I shoot a three shot 100 yard group to check the sites . Most of the time I have not needed to make any changes to my reloads. Some years ago I shot three rounds at a target with the 308 Norma Mag then fired three more rounds to take a pronghorn, mule deer, and elk. Most all of my shots with the 270, 308 Norma, and 340 W Mag has ben a one shot kill, never seen a reason to change bullet, primer, powder, or case brands from my first reloads. I do try new different bullets, powder, primers, and cases in my varmint rifles. I try to get the varmint rifles to shoot one half inch 100 yard groups. There has ben a vast improvement in varmint bullets and powder since I started reloading so I try them but my 220 Swift still likes the old IMR 4064 powder with the bullets I use.-- My big game rifles shot 1 1/2 inch or less groups and the bullets killed the game so I never tried the newer bullets.