That is some bad leading there...I haven't had any leading issues for decades, but unless the barrel is pitted, if there's that much leading something is wrong.
Pounding patches would drive me nuts. I use different methods to remove leading quickly, but I just hate leading so I would try to figure out the problem and fix it rather than figure out creative means to try to remove it later.
But there are only a few things that will cause leading that bad. I would look at alloy, too small a diameter or a different lube. Paper wrap or powder coat keeps things clean if it's legal for your matches.
