Mortar Facts

Miscellaneous notes about the 4.2" chemical mortar

The Four Deuce (aka the Goon Gun)
The Goon Gun's replacement
Mortars in beach bombardment
Ammunition malfunction
Sabotage?
The 4.2 with the Marines in Vietnam


The Four Deuce (aka the Goon Gun)

For photos, descriptions, specifications and interesting background and commentary on the two main models of the 4.2" chemical mortar, check out the links below.


The Goon Gun's replacement

The 120mm smooth-bore mortar, firing fin-stabilized shells, has replaced the goon gun (aka four deuce) in the U.S. Army. For photos, specifications and other information on this weapon, see the Military Analysis Network.


Mortars in beach bombardment

On 9 January 1945, 4.2 inch mortars mounted in LCI(M)s (Landing Craft, Infantry, (Mortar)) participated in the naval fire preparation for the assault by the 37th and 40th Infantry Divisions on the beaches of Lingayen Gulf, Luzon, Philippine Islands.

The following is excerpted from U.S. Army In World War II, The War in the Pacific, Triumph in the Philippines by Robert Ross Smith, Office of the Chief of Military History, Department of the Army, Washington, D.C., 1963 (pages 75-76):

Ignoring the speculations of the assault infantry, guns of naval fire support vessels began their S-day bombardment on schedule at 0700. At first, the battleships, cruisers, destroyers, LCI(G)'s, LCI(R)'s (Landing Craft, Infantry, Rocket), and LSI(M)'s (Landing Craft, Infantry, Mortar) directed their fires upon selected landing beaches. Admiral Kincaid was especially well pleased with the performance of the LCI(M)'s, the main batteries of which were Army-manned 4.2 inch chemical mortars. The high explosive mortar fire, Kincaid thought in retrospect, seemed more effective for beach neutralization than the strafing undertaken by his CVE-based aircraft.

Note: Smith does not identify the CMB manning the LCI(M) vessels. He does identify only two CMBs in his index: the 82nd and 98th. However, Jack Butler states that the CMB in this case was definitely the 98th.


Ammunition malfunction

The overall malfunction record of 4.2" mortar ammunition during World War II was considered generally good. Of the approximately four million rounds expended both in training and in combat, a total of 63 exploded prematurely, causing the death of 38 and the injury of 127 American soldiers. This averaged 1.58 premature rounds in every 100,000 fired.


Sabotage?

At Bougainville, Solomon Islands, February 1944, Jack Butler was platoon exec of the 2nd Platoon, Co. C, 82nd CMB, when it was attached to the Americal Division, XIV Corps. He sent in the following after noting the above item on ammunition malfunction: "At that time (Feb 1944), we still had 6 guns to a platoon, 2 platoons to a company. The 2nd platoon leader was Lt. Vernon Gutman, I was platoon exec. A directive came from CWS (Camp Sibert?) instructing mortar units to inspect fuzes of all shells because some sabotage had been found. We immediately fell to removing and checking fuzes (probably 60-100 HE and WP stacked at the guns ready to fire). Before long, I came across one that was missing the 2 ball bearings, the only thing that held the retaining ring in place, which in turn kept the detonator in the slide from lining up with the primer charge. There was no shear wire to prevent the slide from lining up with the primer. Gutman, an Engineering graduate from New Mexico Military Academy, and I felt certain that it would have been impossible to assemble that fuse without the ball bearings, except by holding the retaining ring in place manually, intentionally setting it up for the slide to line up on initial rotation of the shell. The 4.2 shell M3 w/M5 Fuze was a Rube Goldberg lashup of safety features. The report that '63 exploded prematurely' should be reevaluated with consideration to the aforementioned directive."


The 4.2 with the Marines in Vietnam

Richard E. (Dick) Hulslander, Capt USMC, inactive, sent in the following by e-mail 4 Oct 03.

I was the executive officer or fire direction officer, depending upon whether or not I was the senior lieutenant on board, of Whiskey Battery, 1st Battalion, 12th Marines, a four deuce mortar battery, for six months ending mid-October 1967. For a day or two over four months, we were at Con Thien on the southern edge of the so called "demilitarized zone."

We fired continuous fire for the two companies of 1/9, "The Walking Dead," who were more or less wiped out in early July during Operation Buffalo. We were still there in late September on into October in the action that is covered in Mike Wallace's "The Bloody Sieges of Con Thien and Khe Sahn," a video now sold through A&E on line. The fighting in the time between those two actions was really no less intense.

As for the performance of the four deuce, it was magnificent. The exposed propellant charge was not a good design feature for an environment where the humidity was seldom below 80%. However, if the adage "keep your powder dry" was followed, the rounds performed very well. We used the entire range of artillery fire. A lot of our fire for effects just used high explosive rounds with standard fusing on H&I fires, targets of opportunity and counter battery. We used air bursts, usually VT fuses, but occasionally time over troop concentrations. There was a lot of that on the southern edge of the DMZ during the summer of 1967. Oddly, some time during that summer, we and the grunts out around the perimiter found that delay fuses worked wonders on the NVA's tunnels. I know a precision destruct mission with a mortar sounds ridiculous, but those things were fairly accurate – no eight inch howitzer, but accurate enough. Anyway, the delay fuse allowed the round to penetrate the overhead of the tunnels and then frequently produced an airburst inside the tunnel. The results were reported to be magnificent.

I hope the above helps with your collection of information on a fine weapon. I really think the old four deuce would do well in the battles of today. It provides rapid, accurate fire that is highly effective against troops in the open and light to medium cover. It is highly mobile. It can be fired in or from some tracked vehicles, or it can simply be transported in base plate configuration along with its crew and ammo and set up quickly.

Do you know of any interesting facts about the 4.2" mortar? Please send them to me, Rodney Young, so they can be added here. You can send them by e-mail, or by postal mail to 251 Pine Mdw, Spring Branch, TX 78070.

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