[Cheinen21]

What bore is the most accurate? I started playing pump and I need get my gun just a little more accurate

[aresfiend]

Barrels don't matter for accuracy at a certain point. Once the internal finish is good, they're all the same for accuracy, and since this isn't 1996 all barrels are pretty much the same.

Best for accuracy would be better paint.

[R3L]

You want to underbore to prevent rollout. Accuracy is more of a function of quality paint and a clean barrel.

If I was buying barrels today, I would want something in these sizes:
.675
.680
.685
.690 (most stock barrels are around this size.)

So, three new barrels and maybe hold off on the .685 unless your paint is largish.

The key here is having a barrel tighter than the paint you shoot. So you need to figure out what size your paint is locally. I'm in San Diego and all the paint I shoot calls for a 680 or 675.