sorry i know that this a repost, but i cant find the topic due to a lack of a search button. i know something is wrong here. Given: A 9mm round is reffered to a .38 caliber round. A 5.56mm NATO round is similar in dimension to a .223 rem bullet. These are my conversion units: 9 mm- .9 cm x (1 in/2.54 cm)= .35 in 5.56 mm- .556 cm x (1 in/2.54 cm)= .219 in wtf am I doing wrong? explain. edit: what i mean is that a 9mm is similar to a .38 caliber round, not called a .38 sorry for the misunderstanding.