CN-105-57

CN-105-57 is a French 105 mm tank gun of 57 calibre length.

The CN-105-57 was fitted to some variants of the French AMX-13 light tank and the widely-used Austrian SK-105 Kurassier tank destroyer/light tank produced by Steyr-Daimler-Puch. Some of these vehicles were deployed by Qatar during the first Gulf War, and this is the only known combat use of this gun.

The most significant development of the CN-105-57 was the shortened 44-calibre version developed by Israel to fit into the M51 "Super Sherman" tank and known locally as the CN-105 D1. In this guise the gun saw extensive combat use in 1967 and 1973, scoring many victories in engagements with Syrian and Egyptian forces. The full-length gun recoiled too far to fit into even the larger T23 turret used on the M51. Shortening the barrel, fitting a larger muzzle brake and reducing the cartridge propelling charge reduced the recoil to an acceptable length, although muzzle velocity was significantly reduced. Use of HEAT ammunition instead of kinetic energy rounds largely negated this change in terms of target effect, although accurate effective range was still reduced. Despite this the M51 still outgunned the 100mm D-10T gun fitted to the T-54 and T-55 tanks used by Syria and Egypt and was a match for the 115mm gun and armour of the T-62. Ammunition was a modified version of that used in the 105 mm Modèle F1 gun fitted to the AMX-30 MBT, and was manufactured locally by Israel Military Industries.

Argentina also produced a shortened 44 calibre version of this gun, similar to the Israeli version, for use on their Repotenciado upgrade of ex-British Sherman Firefly tanks, and known locally as the L44/57 FTR 105 mm. Although these tanks still had the original smaller Sherman turret, the extended Firefly bustle gave enough space for the recoil within a limited elevation arc but left a very cramped turret. Ammunition was likewise a locally-produced modified version of that used in the AMX-30 105 mm Modèle F1 gun, but was not the same as that used by Israel. Ammunition was later sourced from FMK.

Many Israeli M51s were sold to Chile in the 1980's and continued in use into the mid-1990's. Together with the Argentine Repotenciado these represented the swansong of the Sherman series as a gun tank, more than half a century after entering service. Some of the individual base hulls were by then more than 40 years old. Use of the shortened derivatives of the CN-105-57 was then unique to South America.