After about 100 rounds of rws subsonic hp, I decided to break out the bore scope and have a look. No carbon ring. Just a few small streaks of lead. As Joe says, don't break out the bore scope unless you want to clean the barrel. I wanted to try something different, so I made a couple of passes with lead remover cloth. It did ok, but left lead in the barrel. I tried something that I have been using for a long time. Remington 40x bore cleaner. Ten strokes and no more lead and left the bore like a mirror. I'll have to start using it more often. I use 1 1/8 inch patches with a bore tech 22 rimfire jag and 22rf rod. Nice and tight but not too tight.
I don't know what type of lube rws uses, but no hint of a carbon ring. Now to reseason the barrel and put some rounds down range.