KS-23

The KS-23 is a Russian shotgun, although because it uses a rifled barrel it is officially designated by the Russian military as a carbine. KS stands for Karabin Spetsialniy, "Special Carbine". It is renowned for its large caliber, firing a 23 mm round, equating to 6.27 gauge using the British and American standards of shotgun gauges and approximately 4 gauge using the current European standards (based on the metric CIP tables), making it the largest-bore shotgun in use today.