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M1s Against Tanks: Antitank Rifle Grenades and Launchers

By Michael Popernack

 

Author's note: Reproduced here is an abridged version of the article originally published in the Garand Collectors Association Journal Volume 16 Number 4 and Volume 17 Number 1.

 

Collectors often overlook the use of the M1 rifle as a grenade-launching platform. However, the use of service rifles to fire grenades was a major part of U.S. military doctrine from WWI through the Cold War. Throughout this time the U.S. employed a large variety of anti-tank, anti personnel and signaling grenades. This article will examine the various anti-tank grenades and accessories used on the Garand.

Armored vehicles came to dominate the battlefield early in the Second World War. Infantry without the support of heavy weapons frequently faced enemy tanks. Although experimentation with large caliber anti-tank rifles was unsuccessful, the U.S. eventually developed a series of lightweight weapons that could be operated by one or two men and was capable of destroying tanks. All of these weapons utilized the "Monroe effect," in which a specially shaped charge of explosive converts a metal liner, usually copper, into a jet of plasma that can penetrate armor plate. Originally developed in Switzerland, the shaped charge warhead is best known for its use by the M1 and M9 2.36" bazooka rocket launchers. This type of warhead was also adapted to a series of rifle grenades.

M9 AT and M11 Practice Grenades

The early WWII M9 anti-tank and M11 inert training grenades can be recognized by their blunt nose caps. In service they were quickly replaced by the M9A1 and M11A1 versions with the familiar rounded nose caps. I have no evidence, but speculate this was to detonate the warhead farther from the target allowing the Monroe effect plasma jet more time to develop. Several later versions produced in the early 1950s differ mainly in the construction of the stabilizing fin. The M9 weighed 21 oz. and used an 8 oz. warhead to penetrate approximately 4 inches of armor under ideal conditions. It was armed before firing by removing a safety pin, similar to a hand grenade, and detonated by an impact fuse. The grenade needed to strike as nearly perpendicular to the target as possible to detonate reliably. The Army field manual FM 23-30 lists a 215-yard range when fired from the shoulder with the M3 grenade-launching cartridge and 315 yards with the addition of a M7 auxiliary cartridge. In practice the M9 was frequently used against enemy bunkers and pillboxes as well as armor. By the end of the Second World War the M9 series as well as the 2.36" bazooka proved ineffective against the latest German tanks. The M11 series practice grenades continued to be used in training into the 1960s. They were used to simulate several smoke and flare grenades. M11A2 through M11A4s can be found by collectors with some searching, but the early M11 is quite rare.

M28 AT and M29 Practice Grenades

Late in the Second World War the M20 3.5" "Super Bazooka" was developed to replace the ineffective 2.36" version. Rifle grenade development paralleled bazooka technology in the early 1950s with the development of the M28 Antitank and M29 Practice grenades. They replaced the M9 and M11 series grenades. It was discovered early in the Korean War that the Soviet designed T-34 tank's frontal armor was nearly immune to the smaller warheads. The United States along with most NATO countries adopted a version of the Belgian (Mecar Industries) "Energa" 75mm grenade. The larger warhead of this grenade was more effective against the thicker armor of Eastern Bloc tanks. The M28 used a bore safe fuse that was armed by firing the grenade; this was more reliable and more foolproof for the soldier, since there was no safety pin to forget to remove. The pointed fuse extension on the nose of the grenade is lacking from the M29 practice version. Both versions of the grenade weighed 22 oz. and were packaged in waterproof fiber tubes with one M3 and one M6 (M1 carbine) cartridge. Little is known about these grenades and good examples are difficult for the collector to find.

M31 AT and M31 Practice Grenades

By the early 1960s, the M31 series of grenades replaced the M28. The M31's major improvement was the use of a piezoelectric crystal fuse to replace the earlier impact percussion type fuse. The impact fuse used an inertial striker to detonate a primer, when the grenade struck the target, was essentially unchanged in principle since the War with Mexico. The piezoelectric crystal generated an electric current when it struck the target, detonating the warhead. This was more reliable when striking the target at an oblique angle. The M31 weighed 25 oz. and used a 9.9 oz. warhead to penetrate up to 10 inches of armor plate or 20 inches of reinforced concrete. Range was limited to about 200 yards. The M31 grenade remained in use until the end of the M1's service life and was also used with the M14 rifle and M76 launcher into the 1970s. These are the easiest grenades to find in unissued condition, frequently in a fiber shipping tube with an envelope containing launching cartridges. Enthusiasts enjoy firing M31s because their robust construction allows multiple uses. We will examine firing M31 practice grenades in a future issue.

Rifle Grenade Launchers

Grenades were launched from M1s using the M7 series of launchers. There are a surprising number of variants to collect.

M7

The M7 launcher was developed in 1943 to allow the Garand to fire rifle grenades. It replaced the M1903 rifle with M1 launcher. The launcher was marked with six rings on the tube that corresponded to indirect fire range tables. Anti-tank grenades were usually fired with the grenade fully seated on the launcher tube. Use of the M7 required replacing the solid gas cylinder lock screw (drawing number B8876) with the "cross slot" gas cylinder lock screw (B147851). This prevented the rifle from functioning semi-automatically since the gas used to cycle the action was vented out the valve screw. Even after the launcher was removed it required 1 or 2 cartridges to be fired cycling the action manually before the valve would close and the rifle would function normally. In January of 1944, production began on the poppet gas cylinder lock screw (B7310079), which had a spring to close the valve as soon as the launcher was removed. M7s were originally issued with a new valve screw to replace the early solid screw, partially accounting for the rarity of early solid lock screws today. It was also necessary to fire grenades from M1s with the "new" B147568 operating rod spring because the "old" keystone spring would allow the follower rod to dismount when firing grenades. In early 1944, the long fork follower rod was introduced that helped address the dismounting problem. More M7s were produced than any other launcher, but some variants are virtually impossible to find. Many were supplied as military assistance during the Cold War and were modified or copied for foreign production. Later, many of these were re-imported and added considerable confusion to collectors. Bill Ricca examined M7s in detail in Vol. 1 No. 2 of the Journal. The following is a brief synopsis of known manufacturers.




Knapp Monarch Co.

During 1941 through 1943, the Knapp Monarch Company (KM) produced the M1 launcher for the M1903 and the M2 launcher for the M1917 rifles. They were given a contract for 250,000 M7s in March 1943, but had great difficulty meeting the 50,000 per month production quota. Large portions of the contract were canceled and production assigned to other manufacturers. The first 35,678 M7s produced used a machined spring to retain the grenade. In December of 1943, production switched to a coil spring, drawing number A7310031. This change was mirrored on KM M8 (M1 Carbine) launchers. Only KM manufactured this first type and very few survive today. Despite the contract cancellations, KM made more M7s than any other manufacturer.

Fay & Scott

Fay & Scott (F&S) was the second most prolific maker of the M7, and was the only manufacturer not to stake the launching tube to the bracket of the M7 to prevent loosening. Many F&S are welded at this location, usually after Parkerizing. F&S production was allowed to lapse in mid-1944, but revised projected requirements in November 1944 meant they were given a second contract. This may account for the different marking styles (FAY & SCOTT vs. F & S).

International Business Machine Company

IBM was given a contract along with Fay & Scott in December 1943 to help KM meet production requirements. IBM produced a lot of M7s with numerous marking variations; these are shown in the accompanying photo. No pattern is discernable and research is needed.

Alfred Hoffman & Company

Alfred Hoffman & Company (AH) was the last of the original three manufacturers brought in to supplant KM production. AH produced fewer launchers than any other manufacturer. AH marked M7s are exceedingly rare today.

Hawley Smith Machine Co.

The Hawley Smith Machine Company (HSMCO) was a latecomer to M7 production, gaining a contract in November 1944 when projected requirements were increased. They were also the last maker to cease production. HSMCO launchers are also difficult to find today.

Mitchell & Smith

The author is unable to confirm any details about Mitchell & Smith (MLS) production. They made more launchers than AH or HSMCO but fewer than IBM, KM or F & S. They are rarely encountered.




M7A1

In July 1945, the T95 was standardized as the M7A1. This had a spring loaded plunger that pushed against the bayonet lug and raised the launcher slightly when a grenade was not being fired. This allowed the poppet valve to close and the rifle to fire semi-automatically. The Hawley Smith Machine Co. was the only manufacturer still producing M7s when the M7A1 was adopted. They were directed to switch to M7A1 production and new contracts were lent to Commercial Controls and American Type Founders, Inc. After V-J Day all contracts were canceled before any actual production began and the tooling for the launchers was shipped to Springfield Armory for storage. Eventually, the Rock Island produced some M7A1s in the late 1940s. These are marked RIA 7313290 on the side of the bracket portion of the launcher and are rarely found by collectors today.




M7A2

The M7A2 was a slightly improved M7A1 with a larger boss that corresponded to the post-war "humped" B7265871 gas cylinder lock. This better supported the grenades heavy recoil. Later M7A2s used a clip rather than the A7310031 coil spring to more securely retain the grenade. A transitional variant also exist with machining for both types of retainers. All versions were produced only by K. R. Wilson and are stamped KRW C-7265949. The M7A2 was only in production briefly before the M7A3 was adopted and is the rarest of all M1 grenade launchers.




M7A3

The M7A3 launcher is essentially a lengthened M7A2, with nine rather than six rings on the tube portion of the launcher. It entered service in the early 1950s along with the heavier M28 and M29 grenades. K.R. Wilson produced the M7A3, as well as did Sun Ray Photo, Long Manufacturing Division, and Acme Machine Works. They are typically marked with the manufacturers' initials and 7266167. Some M7A3s have a built-in flip up sight (example not available for photograph) that was graduated to match the trajectory of the M28 and M29 grenades. This version is rare and heavily featured in 1950s USMC manuals leading to speculation that they may have been Marine Corps only issue.

Grenade Launching Accessories

Rifle grenades were fired using the M3 grenade-launching cartridge, single loaded into the rifle. The M3 contained 46 gr. Of smokeless and 5 gr. Of black powder sealed with a paper wad and rosette crimp. During WWII the M7 auxiliary cartridge was developed. This was a modified M1911 cartridge case that fit in the end of the M7 and M8 (M1 Carbine) launchers. It contained 20gr. Of powder sealed with a lacquered paper wad and added approximately 50% to the grenade's range. During WWII rifle grenades were generally shipped in a crate with an assortment M3, M6 (M1 Carbine) and M7 cartridges in a cardboard box or metal "Spam" can. During the Korean War cartridges were usually packaged in a small envelope with each individual grenade. By the time the M31 entered service the carbine was no longer used to fire anti-tank grenades and only the M3 cartridge was issued. The M7 auxiliary cartridge was only used with the M9 and M11 series of grenades.


Safety note: The M3 is NOT interchangeable with the M1909 or any other blank cartridge. Many people enjoy firing practice rifle grenades, especially the M31, which is still readily available. Just like firing ball ammunition, it is very enjoyable provided you exercise proper safety precautions.

Aiming the grenades was accomplished in several ways. Early Second World War field manuals gave instructions for marking rifle slings to represent 30, 45 and 60 degrees of elevation when the rifle was fired indirectly, held with the butt on the ground and used to lob grenades at the target.This worked well for antipersonnel or signaling grenades, but anti-tank grenades usually needed to be fired directly at the target, shouldering the rifle normally. A better aiming system was needed and in early 1944 the experimental T59E3 was standardized as the M15 sight. This removable sight attached to a plate on the left side of the rifle stock and could accurately aim the grenade either directly with a peep sight, or indirectly with a glass bubble type level. Early sights are marked: Sight, grenade launcher, M15, with a manufacturer mark, usually an "N" in a diamond. Also, there is usually a drawing number, A7310094, on the peep sight elevation screw. These were issued in a canvas pouch with a M1910 type belt hook, generally marked Case, Carrying 7160198, Bearse Mfg. Co. 1944. S.L.CO manufactured most M15s found today. These lack the drawing number on the elevation screw. They are usually typically found in a pouch marked Case, Carrying 7160198 and without manufacturer or date. Some S. L. Co. M15s use a case with a square, rather than a round flap (see photo). The author speculates this is the last production variant. The M15 sight continued in use with the M14 rifle.


Eventually advances in tank armor and anti-tank missiles rendered rifle launched grenades obsolete. The M72 LAW 66mm disposable rocket took over the anti-armor role.

During the years that the M1 was our standard service rifle, rifle grenades were an indispensable part of the infantryman's equipment. They are an interesting addition to any M1 collection and an important part of the M1s' history.

Special thanks for the research assistance of GCA Members Bill Ricca, Scott Duff and William Thomas. Much research remains to be done on M1 Grenade launchers and anti-tank grenades, as well as other rifle-launched pyrotechnics. The author welcomes any dialog from the membership.

If you would like to learn more about the M1 Garand Rifle you should become a member of the Garand Collectors Association. For more information on this great organization visit www.thegca.org

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