It was done, with paintaking calculations. Then the thread wa gone, long before the recent crash.
In short:
a 9mm handgun: the bullet will penetrate a couple centimeters, leaving a wound and a hell of a bruie. Bit it won't kill him.
Anything more energetic, like AK: he'll be as perforated as a regular guy.
I think it was made the beast in that fic, when he, a a small girl, got into Alucard's fight the day before he was going to Hogwarts. The little Ranma returned home, and started pulling bullets out of herelf with tweezers. She got all except the one that lodged itelf deep into her liver. And despite that she still tried to fake being Ok, to not mis going to Hogwarts.
That's very realitically Ranma. Not so much bullet-proof as able to go on despite wounds, and healing at a fantastic rate.
P.S. And my keyboard has key s malfunctioning