.38 ID Help Please

This one should be easy for you guys. I think I’m so tired that I can’t ID this cartridge.

It’s a rimfire with a “U” right in the center of the bottom.


Base and neck: 9.62mm (.379 in)
Case length: 22.3mm (.878 in)
OAL: 34.98mm (1.377 in)

Thanks in advance.


I’d say 38 Long RF made by Remington