I have an Ion in my team, that I built that runs 1100 shots from a 1.1 4500...so yes, you can make them more eficient.
A bad barrel to paint match will mildly affect efficiency, as will lots of porting and a long barrel.
The main concern with paint to barrel is accuracy can be hindered...still, there is a train of thought that sasy, at least with a large bore barrel, you know your paint will come out!