Bullet wt. has a role also.. a 223 at 3000 fps. with a light bullet will be safer than say a .30-06 with a 150 at near that speed...also style of bullet has something to do with it..FMJ bullets would bounce more than say a soft point...this is why the .22 cal. like 222, 223 and 22-250 are popular with varmit shooters everywhere...their soft point and hollow point bullets are made to "blowup" on impact...the faster the bullet and the lighter the bullet the greater the chance of blowup.....