I’m pretty sure the term “gunslinger” is/was slang for a man who has sex with a lot of women. But try as I did, I could not confirm my theory through any real or online dictionary I found.
Is my usage correct, or am I imagining the whole thing?
You’re almost certainly imagining it.
I think that the term may have been discussed in a previous thread, but maybe not.
In any event, the term gunslinger is first recorded in English, according to Lighter (RHDHAS), in 1928. It was a term that simply meant “a western gunfighter.” Used in Western pulp fiction about that time.
I’ve never heard of your defenition stuyguy. However, I consider myself a ‘gunslinger’.
I’ve got plenty of weapons, tons of ammo, and a circulation system full of piss and vinegar.
However, Tripler’s Law still stands. 
Tripler
Lotsa guns, I do. Just not a lot of ‘action’.
I’ve also never heard of your definition, stuyguy.
(And you’d think I’d know!)
Dammit. I meant to include my sig on that, but forgot that if you preview, it automatically unchecks the sig box. Fooey.
It’s a natural extension, and I’m sure that someone has used it that way, but it’s hardly standard. When not referring to an actual slinger of a gun, “gunslinger” is used to refer to someone with the gunslinger attitude or ethos: certain police officers or military personnel, certain business types, some athletes, etc., all have this “never back down, last man standing” way of doing things.
As a follow-up to NameTag’s comments, we used to use the term “gunslinger” to refer to the computer consultants businesses used to hire to solve some sort of critical problem. They’s ride in, solve the problem, and then ride out.
(Nowadays, though, they arrive with a forty-man management team which builds a permanent encampment in your offices and never leaves…)
After saying there is no connection, I do have to at least offer a memory.
In 1961, Bo Diddley put out an album entitled Bo Diddley is a Gun Slinger. While I don’t think it meant anything about his success with women, I had to at least offer it.