what makes up the residue in the choke tube?

[garrett]

When cleaning my M2 tactical, the choke tube always has a firmly attached layer of black residue that needs to be scraped out with a screwdriver - the wire brush won't remove it. It only forms on the receiver side of the choke tube, and is usually a band that's about 6mm wide.

Am I over-oiling the tube (is it cooked oil?), or is this residue from the plastic containing the shot as it's condensed in the choke? I think it's the plastic, but it's odd that it forms in the same spot all the time, and is so hard to remove!

 

Just curious, thanks

[harrydog]

My guess is that it's from the plastic wad material, like you said.