it will still shoot perfectly fine, i have never ever changed from a stock barrel on any of my egos and they all have ball on ball accuracy regardless of paint
Eclipse's stock barrels are great, as has been said. That kind of bore difference isn't going to make a big difference, and matching too close would probably just end up with a bunch of barrel breaks when you consider swelling etc. in hot weather. You're grand mate
If you want to blast at 20+ balls per second then you can't really have the bore too tight, the balls take quite a pounding and you actually need the gas to be able to flow around the ball.
Matching paint to barrels closely is better for slower rates of fire and for guns where the ball rolls out the barrel if you don't.
If you look at the old pump guns then the ball won't usually fit in the barrel at either end.
Basically for barrels you have to balance speed against accuracy and an ego is all about speed.