Well...the thing is. The barrel chart here only has one bore size for the boomstick, which is the standard bore size .688. Dye also makes other bore size boomsticks too. They have the .684, .688, and .692.
Ah ok. I don't have calipers so I used several paintballs (some no name brand) and put it in the barrel. I then compare it to 2 other barrel that I know the bore size of. The other 2 barrel was a CP one piece (.689) bore and Stock omen barrel (.690). I test how many would fit in it perfectly without rolling or having to blow out too hard. And found out that it would fit the CP the most, then the Omen barrel, then the boomstick. So I thought it was the .694. But if it's unmarked then it should be a .688. Hmm...well I guess I'm going to have to find a caliper somewhere and use it to measure.