slow turret rotation speed, as the turret traverse was unpowered and the crew had to use a hand crank to rotate the turret. It took approximately 80 seconds to rotate a full 360 degrees. Total M10 losses in the European Theater of Operations to all causes were 539. Despite not adhering strictly to the tank destroyer doctrine, the M10 still achieved impressive scores against enemy tanks. A US Army study of 39 tank destroyer battalions found that each destroyed, on average, 34 tanks, 17 towed guns, and 16 pillboxes. The tank destroyer battalions in the Third Army claimed the destruction of 686 tanks and 238 self-propelled guns. The highest-scoring tank destroyer battalion in the European Theater, the 823rd Tank Destroyer Battalion, claimed to have destroyed 113 panzers, including 27 Panthers and 18 Tigers, using towed guns and M10s. The 773rd Tank Destroyer Battalion also claimed to have destroyed 113 panzers, with the 702nd Tank Destroyer Battalion claiming 103. The 601st Tank Destroyer Battalion, which fought in North Africa, Italy, and Europe, claimed to have knocked out 155 tanks and self-propelled guns. Tank destroyers in the European Theater fired approximately 11 high-explosive (HE) rounds for every round of armor-piercing (AP) ammunition, an indication of their use in general support duties in addition to the intended mission of anti-tank defense. Variants 3-inch Gun Motor Carriage T35 (Prototype): M4A2 medium tank chassis 3-inch Gun Motor Carriage T35E1 (Prototype): Redesign of T35 with thinner sloped armor. Turret design changed and vehicle standardized as M10. 3-inch Gun Motor Carriage M10 3-inch Gun Motor Carriage M10A1: M4A3 medium tank chassis 3in SPM M10: M10 in British Army service that was equipped with the 3-inch gun M7. The M10 with the "wedge" counterweight was designated 3in SPM M10 Mk I The M10 with the "duck bill" counterweight was designated 3in SPM M10 Mk II M10C or 17pdr M10: M10 in British Army service that was equipped with a 76mm Ordnance QF 17 pounder Mark V gun as used on some British tanks. They can be identified by the muzzle brake at the end of the barrel and a counterweight behind the muzzle brake. Post-war the name Achilles has become associated with the 17pdr; contemporary sources referred to it as a "Firefly", not to be confused with post-war use of the name for the 17pdr Sherman tank. M35 Prime Mover: Turretless M10A1 used as an artillery tractor 3in