igh-velocity CN 75-50 75 mm tank gun. While the tank's main gun was considered satisfactory, its armor was deemed to be too light. Eventually, Israel did purchase the AMX-13, but, in a similar parallel development, it was decided that the 75mm main guns of the AMX-13s Israel bought would be grafted to the more-familiar and the better-armored hull of the American M4 Sherman medium tank, which was the standard tank of the IDF's armored units (a large quantity of post-WWII Sherman tanks ended up under Israeli military service from 1948 onwards) during the period of the early 1950s.[1]

This project started in 1954 and in 1955, a prototype turret was sent from France to Israel.[2] In March 1956, Israeli Ordnance Corps military facilities began to convert (up-gun) their Sherman tanks with 75mm tank guns of AMX-13s bought and received from France.[3] The 75mm tank gun was known in Israel as the M-50 and, as a result, the up-gunned Sherman was designated as the Sherman M-50.[2] The M-50 was similar to the WWII-era British Sherman Firefly tank in that it possessed the original smaller type of Sherman tank turret (as used by US Shermans which carry the original 75mm M3 tank gun) which was fitted with a large counterweight at the turret's rear end to balance the weight of a longer and heavier tank gun.

The first 50 units were based on M4A4 hulls, had a Continental R-975 gasoline engine and VVSS suspension. However, the increased weight of the vehicle combined with narrow tracks led to poor off-road mobility. It was also putting too much strain on the engine, resulting in frequent mechanical failures. Consequently, for the rest of the conversions, hulls fitted with HVSS suspension and Cummins V-8 460 horsepower (340 kW) diesel engine were adopted.[4] These subvariants were sometimes referred to as the M-50 Continental and M-50 Cummins. Diesel engines were also preferred since diesel fuel is less flammable than gasoline, which factors into battlefield survivability.[5] In total, about 300 M-50s were built by 1964 (though it's possible that this number includes 120 155 mm self-propelled guns on Sherman chassis, also designated M-50).[3]

This same gun was also fitted to a number of M10 tank destroyers.[6]

In the 1960s, 180 Sherman tanks received the even more powerful French 105 mm Modèle F1 gun, shortened into the CN-105-57. The barrel length of the gun was reduced from 56 caliber to 44 and it was equipped with a unique double-baffle muzzle brake; ammunition was altered to use a smaller cartridge. In Israel the gun was designated M-51 and the tank the Sherman M-51. M4A1 hulls and the larger T23 turrets (from 76 mm armed Shermans) were used for the conversion. All tanks were fitted with Cummins diesel engines and HVSS suspension. The tank was displayed to the public for the first time during the Independence Day ceremony in 1965.[7]

Abroad the M-50 was known as Super Sherman (the "Continental" variant as Mark I and the "Cummins" variant as Mark II) and the M-51 as either Super Sherman, Isherman (i.e. Israeli Sherman) or M4A1 Revalorise. These designations were never used in Israel. The only tank model designated Super Sherman by the IDF was the M4A1 with 76 mm M1 gun and HVSS suspension, which was named Super Sherman M-1.