The Thing! – M50 Ontos

Several folks mentioned the M50 Ontos (Greek for “The Thing”) in comments about the M56 Scorpion.  Rightfully so, as the two were somewhat contemporaries and initially conceived to fill the same basic airborne anti-tank requirements.   Each represented a different approach, in the days before guided missiles, to providing a heavy anti-tank weapon to the infantry.  While the M56 was for all practical purposes a motorized 90mm gun, the M50 used a set of recoilless rifles.

The story of the recoilless rifles themselves deserves detailed treatment in a separate set of posts.  Short end of that, in the early 1950s the Army fielded the M40 106mm recoilless rifle (which was really 105mm, but let’s save that for another day shall we?).  This large gun fired HEAT projectiles with an armor penetration of 400mm at a range of 3000 yards.  But the outfit was far too heavy, at over 450 pounds, for dismounted use.  Indeed the outfit pushed the limits of the standard 1/4-ton “jeep.”  What the Army wanted was an armored vehicle armed with the M40.

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M50 Ontos at the USMC Museum - Very Realistic!

Some sources credit General James Gavin with the idea for the Ontos.  However the number of prototype vehicles from the 1950s with recoilless rifles leads me to believe several brains came forward with the idea in parallel.  Regardless the basic Ontos chassis started with the T-55 utility vehicle, which was mostly a five-passenger lightly armored vehicle (the T-56 10-passenger “APC” was also offered).   Between 1952 and 1955, Allis-Chalmers developed a series of recoilless rifle carriers on the experimental chassis.  The T-164 carried four M-40s.  The T-165 mounted six.  The T-166 featured one rifle in a dis-mountable configuration.  And the un-built T-167 was to have eight!

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Front View of the M50

The Army liked the T-165 and proceeded to conduct advanced tests.  Dressed out, the T-165 weighed over 8 tons.  The Army actually ordered quantity production before canning the project in 1956.  Officially the Army cited the vehicle’s high profile, the limited ammunition supply, and external reloading procedures.  While not directly competing with the Ontos project, the M56 SPAT then in service weighed less, but left the crew completely exposed.  A better way to put it, the Army was already looking at ATGMs to counter the heavy Soviet tanks.

On the other hand, the Marines had a requirement for the old World War II style tank destroyer units.  They saw the Ontos as the answer to their needs.  Designated M50, the first batches of the Ontos used a six-cylinder truck engine.  After a short, two-year, production run, the Marines received just under 300.  When the engine proved under-powered, the Marines upgraded about half with an eight-cylinder engine, producing the M50A1.  Road speed remained at an impressive 30 mph.

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Running Gear of the Ontos

As mentioned, the M50 carried the impressive armament of six M40 Recoilless Rifles, three on each side suspended from a set of arms.  A traveling brace on the front hull supported the forward barrel of the lower rifles.  The arms connected to a turret, which allowed for an 80 degree traverse, 20 degree elevation, and 10 degree depression.  Instead of elaborate sighting arrangements, above the upper four rifles was a .50 caliber spotting machine gun.  The .50 caliber rounds followed a similar ballistic path to the big rifles.  So the commander simply fired the .50 cals and walked the larger rifles onto the target.

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Right Side Set of Rifles - Note Spotting MG

Three men crewed the Ontos – commander, driver, and loader. The rear compartment was so cramped that often the loader sat to the side of the turret.  In addition to the six rounds in the rifles, a tray under the crew compartment carried twelve more rounds.   A .30 or .50 caliber machine gun on the turret provided close in defense for the vehicle.  The armor was enough only for light arms and shrapnel.

The Ontos remained in Marine inventories as the first units deployed to Vietnam in the 1960s.  There the “Thing” saw wide service, but met practically no enemy armor.  Instead the big 106mm rifles fired high explosive rounds against enemy bunkers or M581 anti-personnel rounds.  The later, with a range of around 300 yards, fired 9500 flechette, with legendary effects against troops staging massed assaults.  The M50 appeared on news footage during the battle of Hue in 1968:

[youtube=http://www.youtube.com/watch?v=OUpl4vf5juA]

How’s that for some retro ‘splody?

You might also check out a rather extensive collection of photographs, resources, and links on the Ontos Crewmembers memorial webpage for more on the Ontos in Vietnam.

The Marines began phasing out the Ontos in 1969.  Some passed to Army units in Vietnam, who briefly operated them for base defense.  But after ten years of service, and no production lines, the Ontos rapidly faded from the picture to be replaced in their original role by TOW carrying jeeps and helicopters.

If I had to rate the Ontos, from the historian’s perspective, I’d call it rather useful but none-the-less an evolutionary dead-end.

Dragon Tales

One of the jobs I had when I was a young troop was Dragon Gunner. By the time I was a Dragon Gunner, they were pretty long in the tooth and not very highly thought of. But think about this: back before you could buy a pocket calculator, the Army had fielded a guided missile that could reach out and destroy a tank over half a mile away, and yet was small enough and light enough for one man to carry.

The Dragon, or M47 Medium Anti-Armor/Assualt Weapon, was first issued in 1975. It was a man portable guided missile that used wire guidance technology called SACLOS-Semi-Automatic Command Line of Sight. Basically, when the missile was launched, it trailed to very thin coppper wires behind it. It also had a flare in the rear of the missile. The sight unit tracked the flare and saw if the flare was in the crosshairs or not. If the missile was not in the cross hairs, the sight sent a signal by way of the wires for the missile to go up, down, left, or right. All you had to do to guide the missile was keep the crosshairs on the target. But that is easier said than done. Dragon gunners spent a lot of time practicing this skill. Since the missile cost about $10,000, they didn’t let us shoot all that many for practice. Usually, a device that fired a powerful blank cartridge was used. One of the other things that made it tough to aim was the launch itself. The missile used a small rocket to propel itself out of the launch tube.

[youtube=http://youtube.com/watch?v=xu7HjKR4I3U]

That’s a missile being shot from a test stand. In real life, it looks pretty much the same and it takes practicee to avoid flinching. If you flinch, you tend to point the sights at the dirt. The missile quickly obeys and flies right into the dirt. That’s not what you want.

If you look closely at the photo above, you’ll see a bunch of dimples on the side of the missile. These are the rocket motors that fly it to the target. Since the back end of the missile is taken up by the wire spool, the flare and the starter motor, the engineers had to put the sustainer motors somewhere else. Also, they had to figure out a way to control the missile in flight. They came up with an unusual method. There are 32 pairs of motors on the missile. While the Dragon is flying, it is spinning like a bullet. Pairs of motors will fire, sounding like a “pop” to boost it on its way. If the missile is not in the crosshairs, other pairs of motors will fire to push it back onto the right path.

Here’s a video that demonstrates the launch and if you listen closely, you’ll hear the pop-pop-pop.

While the Dragon was a pretty impressive weapon for its day, it had its problems. Its range was only 1000 meters. That’s right about the maximum range of the machine guns mounted on all the vehicles it was shooting at. Since it took 10 seconds  for the missile to fly that far, the bad guys had a fair chance of spotting you and shooting quite a few bullets at you while you tried to guide the missile. They didn’t even have to hit you. If they made you flinch, you’d miss the target. That was the other big problem. You had to keep the crosshairs on an often moving target. Even heavy breathing was enough to make this difficult. Getting shot at didn’t help. Still, it was better than no anti-tank weapon at all.

With these shortcomings in mind, the Army developed the replacement for the Dragon. The Javelin has twice the range, is faster, has a better warhead, and has a fire and forget capability. Once the Javelin gunner fires, he can duck for cover or start reloading while the missile guides itself to the target.

[youtube=http://www.youtube.com/watch?v=8VdRnY-TUb4]