Originally Posted by Pb_for_me
So you don't think I'll need to overbore?
Completely depends on you
The only time you would really need to overbore is when you're shooting garbage paint that is horribly inconsistent. In my experience, marballizers have been solid, so you wouldn't need a crazy overbore. Even field paint is fine most of the time.
I like overboring better, but that's a whole debate in itself. I was shooting marbs last week with a .687 and the balls were rolling right out. It was about 35F, so it was a cold day. You should be fine between a .685 and a .691, so I'd recommend a .685, .687, .689, and .691 if you want to really play with the bore. If you're just looking for something that will shoot alright, maybe space it out a little more, .683, .687, .691, .695. That would give you more range, but less play within that range. I don't think you would ever need to go smaller than a .683 or larger than a .695, unless you shoot reballs (which I think are .675?)
What do you mean by inconsistent with your .689 CP? Barrels don't affect accuracy, so if you're looking to improve accuracy, you're better off just upgrading the bolt or gun. If you're looking for less breaks or better efficiency or different sound signature, a barrel kit would be the way to go. If you're having break problems with the .689, definitely go bigger. If the barrel is like super overbored, it could have problems with consistency I guess. Next time you're down at the field and open up a fresh bag, do a blow-test with your barrel. Now that I think about it, when I shot marbs last weekend, they were rolling right out of my .687, so I guess that could be a bigger problem with the .689. If the ball is somewhat snug but flows through with a quick puff of air, the problem isn't the barrel bore.