The Remington MasterBlaster is a big suppressed 8 Gauge kiln gun.
The MasterBlaster system is the most productive and cost-efficient way to remove virtually any type of build-ups in boilers, kilns, silos, quarries or mines. Both the gun and the ammunition provide superior power, accuracy and dependability, shot after shot, at distances up to 300 feet
It fires special remington 8 gauge slugs weighing up to 3 oz. / 1312.5. 8 gauge has a caliber of 0.835″ / 21mm.
Zinc Build-Ups With Hard Exteriors and Soft Interiors
Perfect for self defense
More info here.