improved grouping with dirty barrel

[limbhanger777]

Has anyone notice their barrels produce a substantially better pattern with a dirty barrel?

I am shooting long beard xr's out of a Winchester SX4 with a JEBS HH .650 choke and I consistently produce about 25% more pellets in a 10" circle at 40 yards with a dirty barrel than I do with a clean one

[10gaugemag]

My Gold patterns best with fouling. A fresh clean barrel produces terrible patterns.

I shoot a couple of field loads to foul it up before patterning. Can get 12-15 shots before I notice patterns falling off.

[dirt road ninja]

It is fairly common.