I am doing some testing on that now, what I know so far is that the regular winchester primers while shooting very accurate also are one of the worst for carboning up the plug between where the 209 sets and the touch hole, I have had a fair amout of carbon in as little as a dozen or 15 shots, The Rem STS appears to be much better so I am thinking it may have a lot to do with what primer is used.
I picked up a screw driver that powered by flash light batteries that came with a drill [1/8] and a screw driver tip for 10 dollars it is a wood drill and not as hard as the BP so it is not going to cut it up and it cleans out the carbon in about 2 or 3 seconds, very handy. Lee