I shot/hunted with a .22 mag tubbie, on Ft.Bragg in Spring 1966. I liked it OK, but traded it even for a new 12ga Mossberg 500 Vent Rib Deluxe. I was young, and wanted something different, on a married enlisted man's pay - with a baby on the way.
They were made from the mid-50's ['55 to the mid-60s (64-65)].
The M57 was .22lr, 22" bbl, mine was the M57-M .22 WRM, 24" bbl.
The clip magazine rimfires were the M56 & M56-M, same barrel lengths.
The similar M62 centerfire was available in either .256Win Mag or .30 Carbine, clip, 23" bbl, 1963-69.