The Asefeh rotary cannon that Iran says it is developing for use in a close-in weapon system (CIWS) was finally seen in its entirety on 28 September.
Iran announced in November 2013 that it was working on the three-barrelled weapon, but only the front of the barrels and their muzzle shroud were seen in Iranian media at that time.
The full system was seen in photographs and television coverage of the 28 September event, which included a firing demonstration. The imagery showed that, as previously suspected, the Asefeh is based on the 20 mm M197 rotary cannon fitted to the Bell AH-1J Sea Cobra attack helicopters delivered to Iran in the 1970s.
The M197 is a three-barrelled version of the six-barrelled M61A1 Vulcan aircraft cannon with its rate of fire reduced from 4,000/6,000 rpm to 750/1,500 rpm. Both weapons fire 20×102 mm ammunition: a round with an average maximum overall length of 168 mm and maximum diameter of 29.6 mm.
The Iranian media has reported that the Asefeh is a 23 mm calibre weapon, so would fire either Russian-derived 23×115 or 23×152 mm cartridges. The Fars News Agency released a photograph showing 23×152 mm armoured-piercing incendiary tracer (API-T) rounds present during the Asefeh demonstration. The same ammunition appeared to be loaded into the weapon in the footage shown before the firing demonstration.
This 23×152 mm round is manufactured by the Iranian Defence Industries Organisation (DIO) and is used with the ZU-23 family of light anti-aircraft guns, in widespread use with the Iranian military. It has an average overall length of 237 mm and a belt diameter of 35 mm.
The use of a larger round and heavier projectile with the Asefeh would produce a higher recoil force. It would also require an extensive modification of the components used in the M197, including its barrels, recoil adapter, rotor, bolts, gun housing, feeder, feed belt, and case-ejection chute. The fact that the 23×152 mm case is also belted, rather than rimless like the 20×102 mm, may also have required a redesign of the feed system.
The limited imagery released by the Iranian media made it difficult to confirm that the weapon is of 23×152 mm calibre, especially as coverings had been added to the weapon’s rear housing and part of the barrels.
While it appears the Iranians have completed a complex modification of the M197 design to fire the larger 23 mm round, media coverage could have been manipulated to disguise the fact it still uses 20 mm ammunition.