Winchester Ammunition Bismuth, 20 Gauge, 3, #4, 1oz, Shotshell, 15 Round Box SWB2034XV Winchester Bismuth shatters performance expectations with a premium, uniform shot, which is tin-plated to produce the smoothest, roundest bismuth shot in the industry. To ensure the shot stays uniform and round, Winchester adds a buffering compound that fills voids within the shotshell and cushions the shot upon ignition.