How can I tell the bore on my barrel?

[y2ace]

I have a 14" Cp one piece silver antonized barrel and I want to know what the bore size is to match it up with a good paint, currently I am using powerball but I am wondering if there is a better fit
So is there a tool or something that tells you?

[Q-Ball]

Go to this site and it will tell you what the bore size is and what paint would work well with it.
http://www.escape.ca/~paintbal/The_Gun_shop/paintball_barrel%20chart.htm

[y2ace]

Well the problem is that with my Cp one piece they have s,m,l and I have no clue which one I got, I put a powerball in with the seam aligning with the end of the barrel (horizontal) and there is some light comming through that is about 1/8 of the circumferance.
Is no light better than little light?