I tried to craft a few ranged weapon,hopin in an exeterminus 
and he gave me only rifles.The question is:can he make pistol/crossbow or only rifles?The description say “ranged weapon” but the shape on the craft screen is a rifle,so only that kind of weap can be crafted?
That’s just luck (or lack of it), the ranged category includes all of those item types.
Ranged means ranged. That’s pretty self explanatory. As for the bad RNG, that’s also just bad RNG.