M30 mortar
| US M30 | |
|---|---|
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| Type | Mortar |
| Place of origin | United States |
| Service history | |
| In service | 1951 - Present |
| Used by | U.S. Army, Saudi Arabian Army, Hellenic Army, Brazilian Army, Philippine Army, Philippine Marine Corps |
| Specifications | |
| Weight | 305 kg (672.25 lb) |
| Length | 1.524 m (5 ft) |
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| Caliber | 106.7 mm (4.2 in) |
| Rate of fire | 18 rpm max., 3 rpm sustained |
| Effective firing range | 770 m to 6,840 m (840 yd to 7,480 yd) |
| Maximum firing range | 6,840 m (7,480 yd) |
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 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 to 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. Additionally, imparting a spin to a round causes it to drift away from the direction of fire during flight and the longer the flight (greater range to target), the farther the drift, so the computation for setting the direction for firing at a specific target has to account for this drift.
American rounds are designed to be drop-safe and bore-safe. As such, the fuzes in the rounds for this rifled mortar did not arm unless the round was spun a certain number of times i.e. the round was not armed until it had exited the barrel spinning and traveled a safe distance from the gun emplacement.
WP is white phosphorus ("Willy-Pete")
ILLUM is illumination, a parachute flare round with fixed timed detonation. Deployment height above ground is determined by gun elevation angle and propelling charge.
HE and WP rounds could be fitted with various fuses before firing including a proximity fuse set for detonation at about 30 feet above ground to maximize the effected target area and to spray shrapnel down into foxholes.
There was also a sub-caliber training device that utilized blank 20 gauge shotgun shells to propel an inert training round a few hundred meters. This training was for gunnery skills of laying (in a sense, aiming) the guns.
The M30 entered service with the U.S. Army in 1951, replacing the previous M2 106.7 mm mortar. It was adopted due to the extended range and lethality in comparison to the previous M2 4.2 inch (106.7 mm) mortar, although the M30, at 305 kilograms, was significantly heavier than the 151 kilogram M2.
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Wikipedia