 Rheinmetall 's L / 44 tank gun has a caliber of 120 mm , and a length of 44 calibers ( 5 @.@ 28 meters ( 17 @.@ 3 ft ) ) . The gun 's barrel weighs 1 @,@ 190 kilograms ( 2 @,@ 620 lb ) , and on the M1 Abrams the gun mount weighs 3 @,@ 317 kilograms ( 7 @,@ 313 lb ) , while the new barrel ( L / 55 ) is 55 calibers long , 1 @.@ 30 meters ( 4 @.@ 3 ft ) longer . The bore <unk> and the gun 's thermal sleeve , designed to regulate the temperature of the barrel , are made of glass @-@ reinforced plastic , while the barrel has a chrome lining to increase barrel life . Originally the gun had an EFC barrel life of ~ 1 @,@ 500 rounds , but with recent advances in propellant technology the average life has increased even further . The gun 's recoil mechanism is composed of two hydraulic <unk> and a hydropneumatic assembly . 
