Shot SASS yesterday. 27 rounds of shotgun. I shoot 20 ga, 2 1/2 drams OE 2fg 7/8oz shot, over powder card wad, fiber cushion wads at about 0.5" and an over shot card in a brass Magtech hull. It was bloody hot, like 95 F, and several stages near burned my hand on the barrels walking off the stage. When I got to cleaning, I've never seen anything like it. Amazed I hit anything the last few shots as barrel must have been effectively Super Extra Full choke with all the fouling.
Normally, a good amount of residue will come out with soap and hot water. Even after running soap and hot water through barrels for several minutes, couldn't fit a patch and 20 ga jag down the barrels. A bronze brush was pushing slabs of residue out. It was a pig to clean. Never seen fouling like that.
By contrast, rifle and pistols, shooting .452 200 grs Big Lube / SPG over 21 grs OE 3fg and a cornmeal filler cleaned up easy with very little residue. So, the lube is the difference.
Anyone have any tips for reducing fouling in SG loads? Lube between the two fiber cushion wads?