The M30 107mm heavy mortar is an American rifled, muzzle-loading, high angle-of-fire weapon used for long-range indirect fire support to infantry units.
Design[]
The M30 system weighs 305 kg including the complete mortar with a welded steel rotator, M24A1 base plate, and M53 sight.
A point of interest in the design of this mortar is the rifled barrel. A rifled barrel requires the round to be a very tight fit to the bore in order for the rifling to engage the round and impart rotation on it. But in a muzzle loading mortar, the round has to be loose enough in the bore to drop in from the front. In order to have it both ways, these rounds have an expandable ring at the base which expands into the rifling under the pressure of the explosion of the firing charge which propels the round. Additionall, imparting a spin to a round causes it to drift away fron the direction of fire during flight and the longer the flight, the farther the drift, so the computation for setting the direction for firing a specific target has to account for this drift.
Types of rounds[]
- HE M329A1-max range 5,650 m, weight 12.3 kg
- HE M329A2-max range 6,800 m, weight 10 kg
- HE M34A1-max range 4,620 m, weight 12.2 kg
There was also a sub-caliber training device that utilized blank 20 guage shotgun shells to propel an inert training round a few hundred meters.
History[]
The M30 entered service with the US Army in 1951, replacing the previous M2 107mm mortar. It was adopted due to the extended range and lethality in comparison to the previous M2 107mm mortar, although the M30 was significantly heavier than the M2. Due to this heavy weight the mortar was most often mounted in a tracked mortar carrier of the M113 family. This vehicle mounted mortar was crewed by 5 people: the track commander (mortar sergeant/gun commander), gunner, assistant gunner, loader and vehicle driver. Ground mounting of the mortar was time consuming and strenuous as a hole had to be dug for the base plate of the mortar to rest in, sandbags had to be filled and placed around the base plate to stabilize it and to protect the exposed ammunition. Also, this decreased the accuracy of the weapon as the recoil from firing caused the base plate to shift in the ground. This movement also made the crew have to "lay" the gun back on the aiming stakes more often, causing a temporary lack of fire while the weapon repositioned and re-sighted back to its original reference point.