The M30 107mm heavy mortar is a muzzle-loading, American rifled weapon that is used for long-range indirect firing to support infantry units. The M30 first entered service with the United States Army in 1951 as a replacement for the M2 mortar as it offered an extended range. However, it was significantly heavier. Due to its weight, the M30 was often mounted in a tracked mortar carrier from the M113 family.

This mortar weighs a total of 307.5 kilograms including the complete system with a welded steel rotator, M24A1 base plate, and M53 sight. An interesting feature of this system’s design is the rifled barrel of the mortar. A rifled barrel requires the rounds to be very tight fit to the bore in order for the rifling to correctly engage the round and impart rotation onto it. It is may be complicated for a muzzle-loading mortar to be rifled, as the round must also be loose enough in the bore so that the round may be dropped in from the front. The rounds must have an expandable ring at their base that can expand into the rifling when under the pressure of the explosion created by the firing charge that propels the round. The computation for setting the direction for firing at a specific target must be carefully calculated, as imparting a spin to a round may cause it to drift away from the direction of firing during a flight – the longer the flight or range to the target, the farther the drift.

M30 mortars may fire several different types of rounds:

• HE M329A1 – Maximum range of 5,650 m (6,180 yds.)

• HE M329A2 – Maximum range of 6,840 m (7,480 yds.)

• HE M34A1 – Maximum range of 4,620 m (5,050 yds.)

• WP M328A1 – Maximum range 5,650 m (6,180 yds.)

• ILLUM M335A2 – Maximum range – 5,490 m (6,000 yds.)

HE and WP (white phosphorus) rounds can be fitted with different with various types of fuses before firing to maximize the effected target area; a sub-caliber training device that uses blank 20-gauge shotgun shells to propel the round a few hundred meters as training for gunnery skills.