There are many different sizes of NRA bullseyes, depending on the type of competition. I shoot indoor smallbore rifle & pistol during the winter and the scoring rings are different, even between rapid fire & slow fire pistol. And, on the rifle target, the 10 ring is a circle of about 22 caliber. There are probably many here that know the exact sizes of the bullseyes for various events and I'm sure they'll have some input.