Some say V3's seal better than V2's, I find it's depending on the gun itself. My UMP(v3) gets amazing range, but so does my G3 (v2), but it takes alot of effort to get the same performance out of my M4 (v2)

Maybe something to do with the crappy design of the M4's nozzle/hop up unit and it's mounting method? I've never seen M4 type guns shoot far. My MP5 would always outrange them, even at lower fps, largely because of the solidly held hop up unit and barrel.