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 American standard of shotgun gauges and approximately 4 gauge using the current European standards (based on the metric 'CIP' tables), making it the most powerful shotgun in use today. By comparison, the Nudelman-Rikhter NR-23 cannon uses a 23 mm round, as does the ZSU-23-4 self-propelled anti-aircraft weapons system.
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