This is really getting off the topic but here goes anyway. The Browning .30-06 water cooled machine guns were still in use in basic training when I was going through in 1965. That might explain why there isn't much US made stuff still around.
Here's something else I've mentioned before, also. In theory, a British tank in WWII could have required as many as four different small arms ammo. There would have been .38/200 for the crew's revolvers, 9mm for the submachine gun they probably had (if it wasn't a Thompson, which was .45 ACP), 8mm for the Besa, and .303 for the Bren that was probably mounted on the roof. At least they didn't have to carry it around.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.