My wife got me a few hundred used golf balls. I run a 1" self tapping screw into them, then hang them by a string at 200 yards. Usually have to paint them orange. I usually use a .223 which goes right thru. Sometimes they'll take a chunk out but usually it doesn't even leave a hole, just a smudge where the bullet goes in and out. FMJ's. Gets them swinging pretty good though. lots of fun.