Semi-autos have always seemed to allow soot/gas to move back in the chamber and cause the brass and chamber to be a mess. My opinion is it is just the nature of the beast. I don`t think you`ll see too much improvement with another powder as far as dirt.

I must confess, I was born at a very early age. --Groucho Marx

Patriotism is supporting your country all the time and your government when they deserve it. --Mark Twain