Yeah, the XR-2. I got like 41 kills and 16 deaths I think with it. It's OP

Yes you can on some of the guns but doing so makes you lose stability and range causing you to have to get more shots on the target at mid range. However at close range you will gain an advantage, but using slow rof high damage guns give you an advantage at mid to long range, in the end it all depends on what playstyle you use.

The time to kill for every gun in the game is insanely fast. This is called balance. People may not like the ttk, but it is balanced.