During the Vietnam War this number had increased to more than 25,000. So, for Simo Hyh's more than 505 kills, more than 13,550,000 bullets would have been needed in Vietnam. He remains the deadliest sniper who ever lived.
Our top picks for the best caliber are .223 Rem, 6.5 Creedmoor, and .338 Lapua Magnum because they're either reasonably priced ammo, incredibly accurate, or excel at shooting long range.