Been thinking about this ... I know my snubby is more more accurate than I shoot it, because I rarely just take aim and fire single action (normally am practicing point shooting and flash aiming). When I do, I do quite well with it, but I don't think I've ever even tried shooting at farther than 7 yards.
But I think there's a difference in accuracy that goes beyond just the sight length, though maybe it's not very great.
Anyway ...
Suppose I take a 2" .38 (or .357) snubby, put it in a vice, and then shoot 5 shots with it exactly in the same position. I can't imagine all my rounds are going to hit in the same hole, so there will be some deviation. Correct? A group of "x" inches.
Now I take my 6" .38 and put it in the same vice, shoot at a target. My guess is I'm going to get a tighter pattern (if the guns are of similar brand and quality, of course).
Then I take my .38 rifle (lever action, of course) and put it in a clamp. I'd think I'd get a better pattern yet. Right?
Can't really test this, but if I'm wrong it shakes up my belief system. I thought that longer barrels put a little more spin on a bullet and stabilized it a bit more by forcing it down a longer barrel and giving it more velocity.