An old time trap shooter I knew used to carry a bit of crocus cloth in his pocket. He would wrap it around his little finger and make a couple of turns in the muzzle of his trap gun. His theory was it roughened the choke slightly which produced a better pattern. Subsequent shooting he claimed, would smooth it back out and he would repeat the process. It was religion to him at a trap shoot. Whether it actually worked or not, I can't say. Trapshooters are well-known for a multitude of idiosyncrasies....almost as much as pigeon shooters.