A quick behind-the-scenes note:
If you’re wondering how we actually prepare for this,
the absolute most important document you can find is the operator’s manual.
These days the TM technical manuals,
sometimes also known as the -10, because -10 means operator’s level,
as opposed to -20 which would be the next level of maintenance.
With it you get all the instructions on how we do everything,
so you may not even need to watch the video if you’ve got one of these.
We’re gonna start out tour of the fighting compartment,
such as it is, with the driver’s position.
Mounting the vehicle—simplicity itself,
my old tanker knees appreciate this.
Come forward to step over the driver’s seat.
You can see that the steering wheel has been cut away underneath
so I have a good bit of room for my knees.
And there I am.
It’s not the most comfortable position in the world, but
I guess I can drive it.
Now I’m actually sitting on a stowage box.
The entire seat will lift up and back.
The seat itself is adjustable forwards and backwards,
and the back-rest will go up or down.
There are two pedals, the brake and the “foot throttle,”
which most of us will call the accelerator.
To the right of that is a little foot pedal for a hull drain towards the front.
The last thing I have on the right here is the primer.
There is also a very large warning sign.
It says “Warning! Brake must be firmly applied and locked before firing the gun.”
We’re gonna come back to this.
So the dash is pretty much what you would expect to find on a vehicle of the era.
On the left-hand side are the controls for the engine itself—magnetos,
starter motor, transmission oil, temperature high, engine oil, engine pressure,
RPMs, and the dial at the bottom shows
how many hours the engine has run, in this case it’s showing 1505.9.
Moving to the right you have the ammeter,
which shows how much the generator is working,
and there’s this toggle for black-out drive, or infra-red drive.
Hi-beam / low-beam is a simple toggle on the far right, the speedometer low and right.
And on the right you’re gonna find the controls for the headlights,
and in a case of “if it works, don’t change it” the headlight switch design
basically stays the same on US Army vehicles for the next 40 or 50 years.
If you’re driving a Humvee in the 1990ies,
you will be familiar with how this headlight switch works.
Very recently they started changing to a push-button system.
Forward is the steering wheel of course.
It doesn’t have a huge range of motion, that’s as far as it needs to go.
Transmission is located on the control stock.
So we’ve got neutral, low-range, high-range, or come all the way down for reverse,
and there’s a very simple indicator which you see through the steering wheel.
To start the vehicle you have master power located at the front left,
so turn that to “on,” and of course make sure the lights and your radios are off.
Make sure your magnetos are off and then hit the starter.
What you’re doing here is very briefly checking for hydrostatic lock,
to make sure that the engine will actually turn.
If this works,
what you do it you turn the magneto to A or B or both,
you prime it a couple of times if necessary,
and then you hit start and boost, and you will come to life,
and you use your hand throttle
or foot throttle to hold it idle at about 1,2000 rpm for the next five minutes,
and you will be ready to go.
Once you get going, the vehicle will do 28 mph in high range,
12.3 in low range or in reverse.
The vehicle won’t neutral steer, it will however pivot steer.
If you lock one track, the other will describe a nine-foot-radius circle.
You are doing all this through a clear windshield in the gun-shield.
The gun-shield itself is the only thing
that could be even remotely considered armor on this vehicle.
It’s about 4 or 5 mm thick,
so it will at least stop the bugs going into your face at 28 mph.
So you’ve been driving around. You’ve had your fun,
and you want to turn off the engine.
Well the first thing you want to do of course,
once you’re in neutral and parked, is you want to hit the fuel-cutoff,
which is this button here. Just push down.
Eventually it will cut the flow of fuel to the engine, engine will die.
Turn off your magnetos,
turn off your master power,
and you are done.
By the way, the little button up here to the top right of the master power, that’s the horn.
You’ve got to have your horn.
So the gunner gets what is probably the most worrying position in the house.
Now initially you don’t think it’s so bad.
I actually have a fair bit of room, the seat is on springs; it’s nice and comfy.
The problem is to his left.
Now when the M56 or the T101 is originally being developed the idea was
you were gonna put the T119 90mm gun on to it.
This became the M36, it’s found on the M47 medium tank.
However it was soon determined
that you couldn’t actually get one of those things onto a T101,
so they started the development of an entirely new 90mm cannon,
the T125, and it was specifically for use on this vehicle.
The T125 became the M54,
mounted on mount M88 on this vehicle.
The M54 could fire the entire range of 90-mm ammunition,
so it was backwards compatible with the earlier M1, M2, M3,
and M26/T8 90-mm guns, and also the M36 of the later type.
Now M36 and M54 ammunition could not be fired through the earlier 90-mm guns.
Their typical ammunition would be the M3-18 armor piercing round,
and this was a 44-pound round
which would punch through about 190 mm of armor at a kilometer.
Now the price for this was the gunner’s face.
The problem was this is such a light vehicle.
As the gunner has his head to the sight,
and he pushes the electrical trigger on the traverse handle,
the entire vehicle is going to rock back,
and video of it is very impressive.
Indeed it is probably safer for him to pull his head away from the sight,
and then pull the trigger while holding on for dear life.
Firing this gun would have been… we’ll call it an adrenaline rush.
Now I’m gonna read something from an official army publication “PS Monthly,”
it’s a sort of comic book, user’s helpful hint guide,
not the actual manual, but it says the following:
“It is possible to fire this gun straight forward,
or at least nearly straight forward, with all the crew in place on the vehicle.
Therefore you can operate in a ready to fire condition
when in immediate contact with the enemy
and can take advantage of sudden contacts.
However, the recoil is going to be most unpleasant
and if the gun is traversed out towards the limits of its travel, particularly to the right,
it’s going to cramp the commander and may injure him when fired.
For anything but sudden around-the-corner shots,
the loader and commander should dismount”.
I have never seen any other user manual that says
“this vehicle kicks so badly you’re better off not on it,”
but that’s exactly what you’ve got with the M56,
which I think is kind of cool.
Anyway, moving on.
So to get going with the gun, you’re gonna want to first clear the gun for action.
What you want to do is remove the canvas shroud
which is covering the ammunition and the breech, the optics and the counterweight.
I should point out early T101s had a T-shaped blast deflector.
The production models had a simpler counterweight
with a hole drilled on each side, such as on this vehicle.
There is a manual safety on the top of the gun.
It’s a simple lever.
With that done, the next thing you want to do
is you want to prime the recoil cylinders, and this is a hand pump.
You pump this backwards and forwards.
There’s an indicator on the back,
which will protrude a certain amount depending on
how much pressure you have in it.
When you’re now loaded and ready to fire, you remove the mechanical safety;
there is an electrical safety switch here.
The gunner then aims by use of the elevation hand wheel and traverse hand wheel.
He’s got 30 degrees of traverse per side,
15 degrees of elevation and a good solid ten degrees of depression,
which will probably do interesting things to your recoil effect.
When you hit fire, hold on for dear life.
Recoil will occur, breach will open up, and the loader will set about his duties.
To aim, the gunner would be equipped with a T126 telescope—direct vision.
It’s selectable power x4 or x8.
It’s graduated with either HVAP T137 to 3,200 meters,
4,800 meters for everything else.
It is mounted on an adjustable mount here,
so there is for bore-sighting you release the locking lever,
you alter the mount position, and place the locking back in.
There is also, on the sight itself a spirit level they can adjust for cant.
And that will help you more accurately hit your target
if your vehicle is not on level ground.
Lastly, to the gunners front, two items of note. First is the air cleaner.
It actually has a little selector for summer or winter setting,
and the fuel filler port.
The fuel tank is 55 US gallons,
which will get the vehicle about 140 miles.
Now we move to the back.
As you can see the loader’s seat is nowhere near where his duty position is.
When the gun is being prepared to fire he’s got to get up,
walk around the gunner, come down,
and then he’s got to open up his platform, which at least is simple enough.
It just hinges back
and falls down.
This now gives him a little bit of working space
that can access the three racks of ammunition, 29 rounds in total.
Due to the communality between all the different guns
you can put basically anything in here from smoke,
white phosphorus, to blank ammo.
So demonstrating how this fits, with a wooden round.
You see that’s about as far as it goes before you start to hit a spring load.
It takes a lot of pressure to come in before you will close down the latch.
Now I’m not going to do that right now.
You can see how quickly the round will come out and hit you
if you weren’t ready for it.
To demonstrate if the tube has a round in it or not,
there is a little pressure sensor here.
All it does is just pass this through the front.
The base of the round will push this up.
If the little nipple here is sticking out,
you know there is actually a round in that tube.
If the nipple is flush like it is now you know not to bother opening up the round.
Loading process is simple enough.
Semi-automatic, so you’ve got to open the breech the first time.
Pull down on the plunger, what we know as the breech operating handle today.
Breech block drops, return the plunger back up to the stowed position.
Throw your round in. Sit back, and hold on.
In the event that the round fails to fire,
well, firstly the gunner has a manual trigger.
He’ll pull sharply down on that and see if it does anything then.
If you have to re-cock, there’s a manual re-cocking lever.
Simply pull back on that, stay clear, and let the gunner shoot again.
If that still doesn’t work, you’ve got a dud round.
Pull it out, put another round in, and continue on.
Outside of feeding the gun and holding on for dear life,
or climbing up and down,
depending on how suicidal he feels, the loader has no other functions.
Also not very well equipped with anything much to do is the commander.
He’s seated to the left of the cannon, above the PRC 10 radio,
and that’s all he’s got to play with.
There’s nothing more to be seen.
Although delivery was supposed to start to the troops in 1957, there was a delay.
Undergoing development at the same time was the SSM-A-23 DART anti-tank missile,
and it didn’t seem to make very much sense to CONARC,
the Continental Army Command,
to be funding two different weapons systems
both designed to be mobile anti-tank systems.
And because the M56 was really only designed for airborne use,
it seemed more reasonable to CONARC
that the money should go to the anti-tank missile instead.
Well the Chief of Ordnance and the Chief of R&D didn’t like this and,
in a situation somewhat reminiscent of WW II,
they appealed for the vehicle to be put into production immediately anyway
because DART wasn’t due to come into service for at least another two years,
and everybody accepted that the M56 did the specifications
that was laid out for it.
However the best they got was a study to determine
whether or not the two systems could work together
or one should be better than the other.
Well it turned out that the study said
that they were complementary systems, not competitive ones.
So the money started flowing.
An order for 160 was placed with Cadillac at a drive-away unit cost of $107,000.
They were issued out on the basis of 30 vehicles for an airborne division.
A subsequent order for 290 vehicles was placed in 1959,
and as an example of how you can buy in bulk and reduce the cost,
the price per vehicle of these was $43,333.
And 99 cents.
The vehicle did see combat service.
The 173rd Airborne Brigade took it to Vietnam,
and it stayed there until about 1970
when it was finally replaced by the M551 Sheridan.
Doubtless the low ground pressure and high mobility was useful,
but the complete lack of any form of protection whatsoever
probably didn’t endear it to people given the environment.
The vehicle did go on to see further service
with the militaries of Morocco, Spain, and South Korea.
That’s it for the M56 Scorpion. We’ll see you on the next one.
Capable of traversing soft and marshy, mud, terrain, stuff,
other things that it might happen to run across, badgers.
Or cargo airport… Airport?
I’m reading the bloody thing and I can’t get it right!
To be transported in a heavy assault… glider.
Or cargo airp… craft. God…!
Gunner pulls the trigger, if it works fantast…
We are back at Tankland, and red legs rejoice,
for we’re in front of a 155mm gun motor-carriage M53.
A overhead protective roof to keep the sun off
while you have your barbecue and bar.
Well the rear of the vehicle seems nice and spacious,
I’m actually standing pretty much at full height.
Until you realize that it’s actually six people in this turret
so things start getting a little bit more cramped,
and probably annoying.