Barrel marked after shooting

[KahrArmed]

I am wondering if anyone has had this happen to their P45. It basically appears after firing, and seems to be residue, but it is hard and you can actually feel it with your fingernail. It comes off with some 0000 steel wool, but I am just wondering if anyone has any recommendations on how to prevent it.
http://i1172.photobucket.com/albums/r561/Armedpi/f4a2e7ca.jpg?t=1336749636http://kahrtalk.com/%3Ca%20href=%22http://s1172.photobucket.com/albums/r561/Armedpi/?action=view&current=f4a2e7ca.jpg%22%20target=%22_ blank%22%3E%3Cimg%20src=%22http://i1172.photobucket.com/albums/r561/Armedpi/f4a2e7ca.jpg%22%20border=%220%22%20alt=%22Uploaded %20from%20the%20Photobucket%20iPhone%20App%22%3E%3 C/a%3Ehttp://kahrtalk.com/%3Ca%20href=%22http://s1172.photobucket.com/albums/r561/Armedpi/?action=view&current=f4a2e7ca.jpg%22%20target=%22_ blank%22%3E%3Cimg%20src=%22http://i1172.photobucket.com/albums/r561/Armedpi/f4a2e7ca.jpg%22%20border=%220%22%20alt=%22Uploaded %20from%20the%20Photobucket%20iPhone%20App%22%3E%3 C/a%3E

[KahrArmed]

No thoughts?

[Mudcat]

Just powder residue or carbon. Happens with every gun I've ever had. The brass case is designed to expand in the chamber and seal it off so the majority of gasses go out the muzzle. That seal is just not perfect as you can imagine and the some of the gasses leak around the case. The result is carbon that you are seeing. Some designs it is more noticeable or visible on than others.

[kerby9mm]

I clean my mk's after every range trip and that is one of the marks to clean. Some solvent and all gone.

[jocko]

its on my PM9 and K(, builds up if u do't clean it to. Iuse a wire gun brush with alittle hoppe#9 and it comes off OK.

[KahrArmed]

Thanks guys! I was worried no one knew what it was. I suspected it was something like that, but wasn't sure because it was so hard to remove.