Every 6 month or a year I break it down and check the mechanism to see if there is any dirt there [ never found any yet] and I clean out around the firing pin, unless I have been using some of the shorter 209 I have not found much there either if I have been trying to shoot up the STS I bought to try then there is a little soot in the firing pin chamber.
No my barrels are the same diameter all the way, I have never heard of one that was not. maybe you should do the cotton ball test for burrs TC uses cut barrels not buttoned barrels and from time to time there are some burrs showing up.