Can short films be rated R?

I'm making a short film for a project and there are several factors
that give it the potential to go into a formal publishing procedure.
(It will be rated, transferred to 45mm film, etc.)

Just wondering, can short films be rated R?

I watch LOTS of movies, but never shorts. I'm more of a hollywood
feature film fanatic.

My movie has lots of bloody graphic violence, sexual innuendo,
profanity and coarse language, and suggestive sensuality.

If short films that aren't associated with the MPAA, can they still be
rated R? If they're rated at all?

Any insight will help