I agree with GeauxTide--an inch or two of extra barrel length doesn't explain that wide of a velocity difference. You're definitely right to question what's going on, Tyyota.
A lot of what is typically looked at for pressure signs in handguns can be really misleading. If your revolver has tight chambers, your brass could still last a very long time and not show any issues, even with scary high pressures. Along with tight chambers, add nice smooth chamber walls and you may not ever feel sticky extraction before pressures get high enough for the cylinder to let go. The end result with such a combination is that it's possible to be at fairly dangerous pressure levels and not even know it. I'm not saying that's what's happening in your case, but it's something to keep in mind.
If you can find someone else with a chrony, see if you can shoot a few strings over it and compare the results with those from your own chrony, just to see how close they are.