3/8" AR500: Non-Magnum Centerfire Rifles (.223, .308, 30-06) & Pistols (9mm up to .44 Mag)
3/8" AR500 is the go to target material for a vast majority of shooters and it's pretty much exclusively what I use personally. If you're shooting magnum caliber rifles you may want to move up to 1/2" AR500 but 3/8" can handle many of those calibers so long as you're shooting at them past 200 yards. 3/8" is rated for non-magnum centerfire rifles at 100 yards (remember to keep bullet velocity at impact below 3,000 fps. Faster calibers need to move the target out further to avoid excessive pitting) and Pistol calibers at 10 yards.