Envisioned by Army Ordnance as a means of giving field-artillery firepower to the infantryman, the M18 was considered to be the largest of the type possible to have the ability to be carried and crewed by one man. Or, as Col. Jim Crossman wrote, it put “rifle accuracy and cannon power on a man’s shoulder”. Weighing approximately 45 pounds versus 2,700 for the 57mm antitank gun and wheeled carriage, it shot a 2-3/4 pound projectile with a muzzle velocity of 1,200 feet per second. It was first demonstrated as the T15 at Aberdeen Proving Grounds in early September 1943 and by early 1945 Ordnance sent guns with demonstration teams to Europe and the Pacific. Initial reports were enthusiastic. It is capable of being fired from the shoulder, off of a built in rear bipod/front monopod arrangement or from the 1917A1 tripod, which is actually the most common means.

There were several shells developed for the M18. The standard HE (high explosive), the HE, AT (high explosive, anti-tank) which used a hollow charge for penetrating armor and a smoke round designated WP for its white phosphorus content. Interestingly, a canister shell was also fielded. This was made of thin sheet metal that contained 133 stacked steel slugs. Upon clearing the muzzle, the sheet metal cover ruptured and exposed the slugs, converting the M18 to a giant shotgun.

The People’s Republic of China (PRC) inherited, or maybe more accurately, captured the design and factory for the Type 36. After World War II, the United States supported the Nationalist Chinese in their war against the communists. Among the help provided were drawings, specifications and technical assistance in producing a version of the M18. When the Nationalists left the mainland for Formosa (Taiwan), they had to abandon the plant to the Reds. The Chicom Type 36 is slightly heavier than the M18 and it has a few smaller differences more based on the manufacturing technology employed than on actual design changes. Like the American version, the Type 36 was usually fired from a tripod though it could be fired from the shoulder as well. An advantage of the Type 36 was that it could fire US or Chicom ammunition whereas the M18 could only use US rounds. The effectiveness of the guns was similar. Effective range was about 500 yards (though some sources say as much as 1,500 yards), armor piercing ability nearly 3 inches and firing rate was between 5 and 8 rounds per minute. By 1968 the M18 and M18A1 were listed in Army Ordnance manuals as being Standard B (limited) issue.

During the wars in Vietnam both the US M18 and the Chicom Type 36 were generously provided in great numbers to allies. The Viet Cong and North Vietnamese Army had plenty and so did the French, the South Koreans and the South Vietnamese as well as US forces.

Just about everyone involved in the Vietnam War put the 57mm recoilless rifle to use, including some naval units on both sides…

An incident told in Brown Water, Black Berets by Lt. Cdr. Thomas J. Cutler, USN, describes the armaments of North Vietnamese Trawler #459 as being 12.7mm deck guns and a 57mm recoilless rifle. These were put to use the night of 15 July, 1967 when the trawler headed for the mouth of the Sa Ky River while trying to run a US blockade and was cornered by several US ships where it came under fire and was destroyed.

The US experimented with the M18 on small craft as well. The Norwegian manufactured NASTY class patrol boats (PTF’s), often manned by SVN LDNN crews advised by US Navy SEALs carried one for use from the bow. Later these were replaced due to backblast concerns. These problems didn’t keep the 57’s from seeing any action. PTF’s were often used to provide transportation and cover for sabotage missions in coastal areas of North Vietnam on their SOG 34 Alpha missions. On one particular mission, an NVN Swatow gunboat ambushed PTF-6 near Hon Me, wounding several South Vietnamese crewmen. With a landing out of the question, they evaded the enemy vessel while destroying a gun emplacement and some buildings with their 40mm, 20mm guns and 57mm recoilless rifles. Along with PTF-3, PTF-6 then turned south and safely headed home.

A MAC-V HQ study in 1965 stated that a favored VC daylight tactic for ambushing riverine craft appeared to be the use of 57mm recoilless rifles supported by small arms fire as opposed to mines. This was due to the accuracy and point target capability of the 57mm. An example of this happened on 07 February, 1966 when VC fired upon the Panamanian ship Lorinda on the Log Tau River in the Rung Sat Special Zone with 57mm recoilless rifle and assorted machinegun fire. The Lorinda made it to its destination but was heavily damaged by this attack. One result of this was the installation of the Mark 48 turret onto Monitor and other riverine craft. This turret on ASPB’s had already received hits from VC 57mm RR fire as well as RPG-2s and RPG-7s with little effect.

Probably one of the best uses for the 57mm RR was devised by the US Special Forces at camp A-103. There were 3 fairly large hills next to the camp and situated on each was a hilltop outpost considered essential to the camp’s security. Since these guns looked down on the camp not only was their accuracy and power appreciated but also the concern for the backblast was essentially removed with the breech venturis pointed at the sky. On the other hand, the VC and NVA took advantage of the mobility of the 57mm RR especially when attacking fixed targets such as A-camps or fire support bases. A typical infantry combat support company was, among others, assigned a 57/75mm recoilless company. These were generally used in a direct fire role in support of larger indirect fire weapons such as rockets and heavy mortars, and usually the last to withdraw when providing cover fire while the heavy weapons packed up and left. The recoilless rifles were also considered to have better accuracy than rockets and were therefore also used against smaller targets such as bunkers and command and communication centers.

Ownership in America today

The US M18 or M18A1 is fairly rare in collector’s hands. Few if any escaped either shipment to a needful ally or the cutting torch. Under US Federal Law, it is classified as a Destructive Device by virtue of its larger than 1/2 inch bore. In speaking with a few enthusiasts, I found that the vast majority of these rifles are built from formerly demilled parts sets. The largest source for these, as well as a good supply of spares is Hayes Outapalik out of Missoula, Montana. Gun Parts Corp/Numrich also lists some parts. Though cases and projectiles are available from several sources, at this time only a brave few are beginning experiments to fire full-bore loads of home rolled rounds. And these are from a tripod with ballistic protection placed around the breech. Most folks own or have made sub-caliber devices (see SAR Vol. 4 #12, Sept 2001). These are available in a surprising variety of chamberings from .22 rimfire up to .50 BMG. The most unusual I heard of was those in 6.5 Carcano. I suppose this makes sense when you realize many of these guns were sold to Italy. A special mention of the .50 BMG unit is required. This actually imparts too much stress to these old guns, especially on the aluminum brackets that hold the tube to the mount whether it is tripod or bipod. The suggested way around this is to either fire the plastic projectile M858 round which has very little recoil, or mount the gun to a recoiling MAG-58 mount without sandbagging the feet. This will allow enough movement to help preserve the rifle’s integrity.

Luckily, there is also an experienced gunsmith out there to put these parts sets together. That’s Steve Carlesco at GSI in New Haven, Connecticut. He has already made several non-firing wall hangers, a few Title 1 subcaliber only rifles and some full bore rewatted 57mm guns. For the latter the customer supplies the pre-approved Form 1.

I should also mention that some experienced individuals in the field of DD’s believe the 57mm recoilless rifle to be dangerous to the shooter. There are a few high wear parts that were intended to be replaced at regular intervals. Without a ready supply of these and a complete record of your gun’s firing history, it is best to listen to the cautions of the experts and follow their recommendations for firing full power rounds if you so choose.

The 57mm recoilless rifle served ably during the cold war. It was portable, powerful and accurate. It gave the infantryman artillery power at a time when similarly powerful field guns weighed thousands of pounds. Yet by the mid-1960’s cheap mass produced Soviet and Chicom RPGs and the US M67 90mm recoilless rifle had rendered the 57 obsolete. For a time though, in a humid simmering cauldron called Vietnam, when the cold war heated up, it was there, doing its duty on both sides of the fence.

Kevin Dockery and Phil Labudde helped immeasurably in the preparation of this article.

Sources:

Part sets, spares, cases and projectiles:
Hayes Outapalik, P.O. Box 8423, Missoula, MT (406) 549-4817
Projectiles and cases only:
Big Sky Surplus LLC, 3018 E. Sinto, Spokane, WA 99202 (509) 535-9486
Gunsmithing, assembly and general advice:
Steve Carlesco, GSI, 41 Main Street, New Haven, CT (203) 467-8437

The one that I own was remanufactured by Black Mountain of Florence, MT for Hayes Otoupalic. They did a fantastic job. I’d dare ya to try and show me where they rewelded the deactivated cut receiver, but it was all done to ATF regulations. The subcaliber device is quite simple yet effective. They take a .50 BMG M2 heavy barrel with two stainless steel washers, one with the outside diameter the same as the inside diameter of the M18 barrel and the other with the inside diameter of the breach. The barrel is then headspaced and both washers are permanently welded in place. There are widely differing opinions on the safety of this style of subcaliber conversion I’m afraid.

The U.S. Military originally trained with a very different subcaliber device, essentially made of a 57mm cartridge case, an inert projectile, a barrel bushing, a machine gun barrel and a lock nut. Simply put, the projectile is drilled through the center to receive a standard A5 .30 caliber barrel, then the subcaliber device is inserted into the M18 chamber using normal loading procedures. The safety issue is the difference in chamber pressure between the .30 caliber and the .50 BMG. The .50 BMG has about the same kinetic energy as an exploding hand grenade. The M18 was designed to vent the violently expanding gas from the 57mm round through the rear breechblock. The escape of these gases is controlled so that no movement of the weapon occurs. This is the recoilless principle.

As a .50 BMG rifle these gases are now contained within the receiver and the M18 breechblock is now acting as the locking bolt. If one takes a close look at exactly how much material is left between the breech block vent holes, one comes face to face with the academic questions, should I stand behind this thing while it is fired? I myself have put over sixty of the Greek manufactured and marked “HXP 74” rounds through this firearm without a hitch. I later examined the breechblock with a magnifying glass and found nothing unusual. That’s not to say something couldn’t happen in the future not withstanding our litigating lifestyle. But in my opinion, it appears to work just fine.

Sighting in this firearm can be a bit of a challenge. The 1917A1 tripod is a given, as many sandbags as you can find and one extra helper wouldn’t hurt. For the target we used a 36” x 12” x 1 1/2” steel plate designed as a counterweight in Otis elevators and donated by them. It was spray painted white so we could see it on the 225 yard berm in Ukumehame firing range. The best way we found to first get in the ballpark was to kneel behind the gun and bore sight straight through the open breech, then bring your M86F telescope traverse and elevation on target. Then load a round, cock the firing assembly and squeeze the handle grip trigger. Even with its muzzle ported for recoil, be prepared. This puppy still likes to come right off the ground, even with the sandbags. After several rounds we heard a loud satisfying gong and watched that sixty pound piece of steel spin like a top.

We spent the rest of the day dinging that steel. I did notice the firearm has a very tight headspace. Closing the rotary breech takes some effort, because of the subcaliber device the original extractor is omitted from the firearm. The first time you try to remove the spent .50 BMG shell you will wish you had fingernails of steel, but most people don’t. What worked best for me was a car tire iron spoon that I painted black to match the weapon.

To complete this project, I had Master Carpenter, Mr. Tom Johnson of Kula, Maui, build an original looking solid wood transit chest, including casters and rope handles. Last but not least, a set of custom oilboard stencils for the chest from Rick Larsen of Westbury, NY. Aloha from the Valley Isle.