Complex sentence: Shotguns larger than 10-gauge are rarely manufactured nowadays; punt guns and special purpose guns like the Russian 23mm KS-23 (approximately 6 gauge) do exist, but are rarely encountered.
Split into simpler sentences: Shotguns larger than 10-gauge are rarely manufactured nowadays. Punt guns and special purpose guns like the Russian 23mm KS-23 (approximately 6 gauge) do exist, but are rarely encountered.