That is absolutely a .22 but I can't tell if it's a CB cap, short, a long, or a long rifle. Need a length reference now (please don't hit me, sorry, lol. )
But I can tell you that the .22 rimfire was never used as a primary military combat round by the US armed forces. It saw some limited use from the late 1940s to the 1970s as a "survival weapon"
(US U2 pilot Francis Gary Powers had a silenced .22 in his survival gear when he was shot down over the USSR.)
Cool found in park about 6 inches deep. Did not find much else some clad one wheaty a pile of pull tabs. Kinda bummed out don't know if I'm working my v3 or just is not much good stuff were I'm hunting.
U.S Cartridge company was in business from 1869 until 1927. They were bought out by Winchester. The .22 cal was already in existence when they started up, so your shell could be from anywhere in those dates.