I have just come across a 22 WRF-REM SPL rimfire that with a U headstamp and the letter S stamped on the side of the case above the cannelure. Can anyone tell me what it stands for? Is it scarce or a dime a dozen.

The “S” stands for Smokeless Powder. You can also find “L” for Lesmoke" powder, “U” for Ungreased and “G” for Greased. These letteres were used from about 1910-1927. After 1927 “S-” = Smokeless “-” = Lesmoke.

Those with the letters are much less common than those without.

Thanks fellas for your much appreciated info.