Reminds me of Borderlands 2 - looks like a hyperion weapon.
Good work. Looks interesting and useful.
You can't rifle or chrome line Titanium for a gun barrel. The Lining must be steel or something of greater hardness on the Brenel scale. Normal bullets would be perfectly practical for the sci-fi esk weapon. The Brass takes in a lot of the heat that a caseless round won't, reducing the heat that way. Even just have a small fan blow on the barrels would help greatly in terms of heat management. however when correctly firing in bursts like any skilled gunner must do, heat is never really a factor. You can try adding in Sci-fi elements if you'd like but it'll work as it is just fine. The gun is fairly logical, albeit different than existing intermediate arms.