It depends on the brand. Sometimes letters indicate features, for instance, a Beretta F is slightly different that a Beretta FS.
Sten submachine gun
the 19th letter in the alphabet
Stevens 940 shotguns have a letter after model number is a way to date this gun?
s for
Science is not an acronym
Herbert Schmidt.
Gun is not an acronym, and does not stand for nor abbreviate any other word.
Soon
what s the meaning of each letter of the word service
In the field of physics, the letter "S" often stands for "second," which is a unit of time measurement.
Stand
Street legal