Not sure on this one stdmstr. I've just received my J&J Edge Elite kit but have been shooting Reactor through .685 bore, and it's been going pretty straight.

Really, without dropping your paint into the fin (whether it's the .683 .686 or .688) it'll just be a guessing game as to which will be the best one for the paint you're shooting. Probably the SAFEST bet would be to get the .688 as it's the biggest fin they have, and by rights should shoot all your paint. As I said, that's the function of a barrel kit. You get to size up your paint for the right bore match.

But in your situation, play it safe and get the .688 fin. That'd be what i'd do anyway. Good luck.

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