It is not impossable to cure the problem to a reasonable extent, I had it really bad since I insist on experimenting with every thing availble I just kept trying, it helped several things when I polished the barrel with jewerals rouge and then Sabot loader gave me a tip on keeping the pores full of BB know its not much more of a problem than Pyrodex.
I would suggest you try APP sticks as they are the least corosive of the subs and I have shot all afternoon with out cleaning or needing to Pyrodex will also work well and if you are really sold on it and willing to go to the trouble of doing it you can make 777 work. Lee