The Thumper: History of the M79 40mm Grenade Launcher

By Will Dabbs, MD

Lamar Bradford had a curious gift. He was raised on the streets in Baltimore. Lamar played a little high school baseball, but gave that up when he dropped out of the 11^th grade. On his 18^th birthday, Lamar’s wealthy Uncle Sam sent him a very official letter.

There was absolutely nothing special about being a young draftee in 1968. Six months after he got his draft notice, Lamar touched down in Pleiku. He knew exactly nobody in the entire godforsaken country of Vietnam. The vagaries of fate and the inscrutable machinations of the Army admin system landed him in the 4^th Infantry Division.

PVT Lamar Bradford was folded into a rifle squad in 1^st Platoon, Alpha Company, 2d Brigade, 1^st of the 12^th Infantry, as a green replacement. His battalion went by the curious moniker the “Red Warriors.” The previous M79 grenadier had lost a foot to a punji pit doped with human excrement. When the First Sergeant welcomed Lamar to the company, he had tossed him a well-used M79 40mm grenade launcher and a Colt M1911A1 pistol. PVT Bradford had fired a grand total of six practice rounds through the Bloop Tube during AIT and he knew how to strip the .45, but that was about it.

The Top Sergeant expected PVT Bradford would need a little refresher training on the Blooper, so he took him to the edge of the firebase with a crate of grenades. He pointed out a scraggly tree about 200 meters away and directed PVT Bradford to blow it up. That was the first time he had manifested the gift.

Three months later, now-PFC Bradford moved quietly through the tall grass alongside LT Dunlap. A lot of the officers Bradford had met in Vietnam were crap. Dunlap was not. He would die for his troops. His men knew this, and they loved him for it.

The NVA sprang their ambush from high ground. LT Dunlap’s platoon was trapped in a scrubby defile at the base of a rock-covered hillside. The two pig gunners reflexively opened up with their M60’s. Everyone else dropped to the ground and began throwing rounds back, most of them at their max cyclic rate. Amidst the cacophony and chaos, American troops began to fall. LT Dunlap pulled PFC Bradford down beside him and shouted above the din.

“Brad, I’m working the company mortars, but that’s gonna take a minute. The ambush position is about 250 meters up this hill to the right. All the enemy fire seems to be coming from that one spot, so it seems unsupported. See what you can do about that.”

Without another word, Dunlap found a shallow spot and got back on the radio. Bradford slithered sideways until he could peer through the tall elephant grass. Satisfied that he had the lay of the land, he carefully raised his M79. He had not used his sights in two months.

The first round coughed out with a dull thunk. Before it impacted, Bradford had another on the way. The two M433 HEDP (High Explosive, Dual-Purpose) grenades exploded in rapid succession, both in essentially the same spot. The incoming fire from the enemy fighting position stopped immediately, and LT Dunlap canceled his emergency fire mission.

LT Dunlap dispatched a squad to clear the NVA ambush site. His men returned with a pair of AK-47 rifles, an NVA helmet peppered with shrapnel, and a tattered NVA flag. They gave the flag to PFC Bradford. Back home, Lamar Bradford was just another street kid. In this curiously deadly place, however, PFC Lamar Bradford was a rock star.

The Tool

The odd single-shot grenade launcher that PFC Bradford carried began life as part of Project Niblick in the 1950’s. Niblick itself spawned from Project SALVO. Both undertakings strived to produce revolutionary advances in infantry weapons in the years immediately following World War II. While most of the Buck Rogers gear that came out of Niblick and SALVO went the way of the dodo, the S-3 grenade launcher advanced to the next stage of development.

The S-3 was a shockingly simple weapon. A single-shot, break-open design akin to your grandfather’s antique single-barrel 12-gauge, the S-3 eventually evolved into the S-5. The S-5 got a new sight system and was subsequently type classified as the M79 in December of 1960.

The first M79’s were issued to U.S. Army troops in 1961 and were quite well-received. The M79 came to be known as the Thumper, the Bloop Tube, the Blooper or Big Ed. Australian operators referred to the weapon as the Wombat Gun. To troops accustomed to the inaccuracy and punishing recoil of rifle grenades, the short range of the hand-thrown sort, and the cumbersome nature of organic mortars, the flexibility, responsiveness, and accuracy of the M79 made it a game changer. The M79 served as the platoon leader’s artillery.

The M79 only has five major components: the receiver and barrel groups, the fore-end assembly, the folding ladder sight, and the buttstock. To operate the weapon the grenadier pushes the swivel latch to the right. Gravity will open the action. The internal hammer cocks automatically when the barrel is opened. Drop a round in place, close the breech, slide the safety off, point the gun at something you dislike, and squeeze. Easy peazy.

The recoil is difficult to quantify. It is more of a shove than a kick. The payloads are invariably weighty, so Physics dictates that the launcher has a little spunk. However, it’s weird. The experience isn’t much like a big-bore rifle or shotgun.

There are two different sighting systems on the M79. The folding ladder sight is graduated from 75 to 375 meters in 25-meter increments and is quite accurate in experienced hands. When folded, this assembly also includes a basic point and shoot V-sight for quick engagements out to 100 meters. An experienced grenadier can also set the buttstock on the ground and use the sling to estimate elevation. The weapon’s max effective range is listed as 400 meters. The trigger guard folds to the side to accommodate gloves if needed.

The M79 is a very simple weapon that fires a wide array of complex ammunition. We lack the space to explore the details today, but perhaps we can do so at a later date. 40mm High Explosive rounds typically travel at around 245 feet per second with a right-hand rotational velocity of 37,000 rpm. This rotation stabilizes the grenade in flight and also provides the centrifugal force needed to activate the spin arming system. Current-issue rounds do not arm themselves until they have traveled about 30 meters beyond the tube. Early Vietnam-era 40mm grenades armed at between 14 and 27 meters.

M79 Specifications

Here are the specs on the M79 grenade launcher:

Caliber	40x46mm
Barrel Length	14.5″
Overall Length	28.8″
Weight	6 lbs (unloaded)
Action	Break action, single shot

Ruminations

Though certainly antiquated in the Information Age, the M79 is innately more accurate than either the M203 or M230 under-barrel grenade launchers. As a result, this old warhorse remains in widespread use around the world. During the recent operations in Iraq and Afghanistan, Explosive Ordnance Disposal units were still using the M79 to detonate IEDs remotely.

There is anecdotal evidence that DevGru SEALs used cut-down versions of the M79 at least as recently as Operation Neptune Spear, the mission to kill or capture Osama bin Laden. These customized M79’s had their tubes trimmed back and their buttstocks formed into stubby pistol grips. While not nearly as effective as the full-sized guns, these compact little launchers nonetheless tossed their antipersonnel rounds much farther and with greater accuracy than might be accomplished with conventional hand grenades. The SEALs purportedly refer to these unique M79’s as their “Pirate Guns.”

The M79 is that rare example of a classic military weapon that just won’t die. Alongside the Ma Deuce .50-caliber machine gun, the M79 fills a tactical niche that hasn’t been bettered even today. The M79 exemplifies the adage that often the simplest solution is indeed the best solution.

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