choke tubes

[garyz]

I was cleaning my choke tube and noticed that the inbound side looks like it has been burned. I scrubbed but no change.
do choke tubes wear out? should I replace the choke, or just shoot until it can't be shot?
it's an invector + choke for a browning bt100, if that makes a differance

thx
garyz

 

[firtree]

Is there any chance that you are seeing wadding fouling? Sometimes
it will leave a wierd residue.

F

 

[garyz]

not sure what the wad fouling looks like, this looks like someone took a torch to it. I scrubbed w/ a toothbrush, but got no change


garyz