The M30 106.7 mm (4.2 inch, or "Four-deuce") heavy mortar is an American rifled, muzzle-loading, high-angle-of-fire weapon used for long-range indirect fire support to infantry units.

The M30 system weighs 305 kilograms (672 lb) including the complete mortar with a welded steel rotator, M24A1 base plate, and M53 sight.

Deployment height above ground is determined by gun elevation angle and propelling charge.

Also, this decreased the accuracy of the weapon as the recoil from firing caused the base plate to shift in the ground.

[citation needed] During the Vietnam War, both the US Marine Corps and the US Army deployed the M30 mortar.