I have a few revolvers that seem to have a decent amount of choke in them at the barrel threads. Playing with pin gauges almost all of my newer revolvers (80's to the present) seem to have some choke. Most of my older revolvers don't (mostly S&W). I have one Ruger 41 mag that passes a .400 pin gauge to the choke point and stops and takes a .398 to get through the choke. I don't see how that can be helping accuracy..
Is it really anything worth dealing with or is there an easy fix. First thing that comes to mind is fire lapping. Done plenty of that on older military rifles but never on a revolver.