XM291

The XM291 Advanced Tank Cannon (ATAC) is an American experimental 120 or 140 mm smoothbore tank cannon. It started development in 1991 as a way to substantially increase the performance of tank cannons against the perceived threat of future Soviet main battle tanks. It can be used in two configurations, one in 140 mm and one in 120 mm electrothermal-chemical technology (ETC).^[1] The XM291 was the first cannon to incorporate a system that counteracted the vibrations in the barrel caused by the tank moving over terrain, using the dynamically tuned shroud (DTS).^[2]

XM291
Type	Tank gun
Place of origin	United States
Specifications
Caliber	140 mm / 120 mm

While it was originally developed for the Block III tank, development of the Block III was halted while the XM291 saw continuous development and was used on other testbeds such as the CATTB and the M1 Thumper.^[1][3]

Ammunition

Table of ammunition^[4]

Designation	Munition type	Calibre	Projectile mass	Muzzle velocity
XM866	Kinetic energy penetrator (KE)	120 mm	5.4 kg	1675 m/s
XM831	High-explosive anti-tank (HEAT)	120 mm	13.6 kg	1145 m/s

Specifications

XM291 (120 mm)^[1]

• Barrel length: 6,731 mm / 265 in (56 calibre)
• Weight (total): 1,451 kg / 3,200 lb
• Weight (breech): 590 kg / 1,300 lb

See also

• XM360, American electrothermal-chemical tank gun