The M10 was the final result of a series of vehicles
intended to give the tank destroyer branch a bigger gun.
It was only an expedient vehicle,
tank destroyers actually wanted something much more mobile,
but they needed something now
and the 3 inch gun motor carriages T24, M5 and M9 didn’t make the mustard.
As a result M10 was put into service.
A lot of them did find their way across the water in Commonwealth service,
the M10 were there known as Gun, 3”, anti-tank, on self-propelled mount M10.
There was, for the British however, a bit of a problem.
The 3” gun was the only one of its type in British service.
As a result this led to logistical problems,
and training problems and it just wasn’t worth the hassle.
It’s actually pretty similar to the problem they had with the 76mm Sherman:
Perfectly fine system, but it used ammunition,
which was not readily available in the British system.
The result was pretty much the same for both.
Remove the 3” high velocity or the 76 and replace it with a 17pr.
The Firely was a different turret, but you get the gist.
It didn’t hurt that the 17pr also had a very significant punch,
but the important part was that it was in British service,
with being produced in British factories,
ammunition was easy to come by and it was in the supply system.
Vehicles which had been converted were known as Gun, 17pr, Anti-Tank,
on self-propelled mount M10.
Very creative name.
After a while the British decided they actually needed something a little bit catchier
and shorter and they came up with the name “Achilles” in early 1945. In order to distinguish between the different marks of M10,
the Achilles Mk1 was the M10 equivalent with a twin diesel engine,
the Achilles Mk2 was the version with the Ford V8.
The Americans would know it as the M10A1. If it had the 17pr they added the identifier C, the letter C.
This was the standard nomenclature for a vehicle which had a 17pr on it,
so for example the Sherman Firefly was known as a Sherman 5C.
As a result the vehicle I’m standing in front of is an Achilles Mk1C.
Now the astute of you will notice looking at the mantlet
that was actually not the end of the upgrades that this vehicle received ,
but we’ll get to that a little later.
As we start our tour of the hull it occurs to me that things
are going to start becoming a little bit redundant:
After all, all the running gear on most of the American vehicles
is pretty much derived from each other,
so in this case the M10’s running gear comes from the M4 medium,
the M4 medium had it developed from the M3 Medium and so on and so forth. However at least the hull on this is not actually an M4,
although it was derived from it, so we’ll start there.
So the purpose of the tank destroyer was
they were supposed to be more mobile than the tanks they supported.
As a result the armor on this is thinner as a concession to mobility.
It’s only 1.5”, sloped at 55.
Aside of that though most of the other features is common to the
American tanks you’ll see behind bushguards, the siren and
servicelight, markerlight.
As you start moving back you can see the hatch is a bit of a design flaw.
You can’t open or close it if the gun is to the front.
Oops. There’s no hull MG (machine gunner).
The Tank Destroyer branch basically found it surplus requirements
and it would blur the line a little bit too much between
an anti-tank gun and a tank.
Not having an MG certainly reduced the temptation to play tank. Indeed though the T49 early concepts a bow machinegun.
Eventually Tank Destroyer branch decided “surplus to requirements”.
The casting at the front for the nose,
which covers the final drive is pretty much standard design of the era
and finally I will point out the blindingly obvious here,
this is a British vehicle, the 17pr of course being a British gun,
these are American markings. No, I cannot explain why somebody in the past time
painted this up as an American tank destroyer.
The Americans did consider the 17pr conversion to be a good conversion,
they liked it, however
because the 90mm could be dropped into the M10 just as easily,
effectively making the M36 predecessor,
there was no need for the Americans to take the 17pr conversion.
The 90mm was in production, they already had ammunition,
so basically for the same reasons the British went with the 17 pr,
the Americans were very happy to continue with the 90mm,
which in fairness is a better gun anyway.
Tracks were common to the HVSS vehicles.
They’re 16 9/16” wide, 6” pitch.
They’re doublepinned, they’re connected by end connectors
which also function as the guide horns. The bogies themselves, 3 per side, each which has two wheels
with the distinctive vertical volute springs within them. Now the bogies could be replaced either as entire components
or as individual pieces within the bogie.
To give you an idea of the tension that goes on these springs,
if you wanted to replace just one of the volute springs
you’d have needed two five-ton jacks to do it. The system itself if you wanted to remove the whole bogie,
there are 16 bolts on the inside.
So firstly you’d have to break track, above the bogie,
just make sure that’s not resting on either the return skid
or the support roller.
By the way that’s also the indicator this is a heavy duty bogie later model
as opposed to the earlier ones which had the return roller on top. Track’s broken, undo the 16 bolts, out it comes, place on the new unit,
16 bolts back on, connect the track, you’re done. This is one of the advantages of the bogie system,
it is very easy to replace due to battledamage or anything else. The other advantage is that it takes no room inside the hull at all.
There are no springs, no bars or anything else.
And this is part of the reason the Germans were very fond
of leaf spring suspensions as well such as on the Panzer IV.
However, of course the bogie system does come with some disadvantages.
In this case, especially on the VVSS, the amount of travel that you have. Now to give an example of the problem,
although this vehicle is rated to cross a 7,5 foot trench,
it is according to the manual limited
in the maximum height of wall it can cross at 18”. A vehicle like this not being able to cross higher than 18”
is what I would call pathetic. And if you think about it though,
because of the way the wheels will travel on their support arms
anything bigger than that is basically function as a chock block,
when it hits the wheel. Now if you did add the grousers,
then what you could do is scale according to the manual a 36” wall. Which is a little bit better,
but then you got to go through all the hassle of adding the grousers
and so on which a lot of the times they didn’t bother with.
The other obvious difference between the M4 hull
and that of the M10 is that the sides are angled outwards.
Now to reduce weight they were reduced ¾” of thickness.
However to add a little bit more of protection you have them at an angle. The catch, well there was actually two of them,
obviously the vehicle is now wider.
This can lead to some difficulties in either narrow roads
or railway loading gauges and so on and so forth.
The other difference is that this is actually a very hard vehicle to climb up on
and my cameraman was noticing the same thing as well.
Ordinarily you come up to the side of the track,
you use maybe the bogie wheel as a footstep and you climb up that way.
It doesn’t work that way with this vehicle, it gets a little bit more complicated. The skirts at the bottom which come inward,
they’re ¼” thick and really they’re not going to stop much more
than a caliber 50 round.
But hey, every bit helps. They are kind of hollow underneath leaving room for the tracks,
the actual horizontal plate for the sponson is at the joint of the angles. The bosses, that you see on the hull side and turret side,
offer additional armour, applique. The armor is spaced, ¾”,
and according to the manual comes in multiple thicknesses, as appropriate. Now the reason they’re here in the first place
was that Tank Destroyer branch were kind of hedging their bets a little.
Remembering that you were supposed to have a mobile vehicle
better than tanks, but you have less armor.
The vehicle wasn’t supposed to slug it out.
What were you going to do?
Well, it turned out in the end that Tank Destroyer branch decided
“you know, just in case we’ll put the bosses on,
maybe we’ll change our mind later.”
Well, that didn’t happen in the end,
really the only users I can find of the additional armor were the British.
I’m not going to say the Americans never put it on,
but by and large they didn’t.
Track tension is a bit of a chore.
Now the first thing I have to do is I have to introduce you to Little Joe.
Little Joe is located just above the exhaust and is a very large wrench. Coming back to the idler system.
Various components to be done here,
firstly you have to unscrew these two locking bolts.
You then screw in the spreader bolt,
and this opens up the casing around the idler arm.
These two little holes here are supposed to hold a retaining clip,
which holds this locking clamp here.
Knock this out of the way it frees up the serrations.
You can then use Little Joe and a couple of lads
to lever the idler wheel forwards and backwards.
When you’re done put back the locking plate,
back onto the clip, loosen the spreader bolt,
tighten the clamps and finally you’re done.
While we’re back here we can also see one of the easiest identifiers
of a Mk 1 or Mk2 Achilles and that is the exhaust. So on this diesel powered system, you have two short little exhausts.
If you were to look at the V8 powered one,
there is actually a large baffle or grill at the rear under the slope. And the other obvious difference is going to be on the engine deck,
but 9 times out of 10, if you’re standing next to the vehicle,
you can’t see the engine deck. Other things here obviously you have your tow pintle
for towing whatever it is someone decided it was a good idea to tow.
A couple of mounts here for your tow cable
and of course all the tools are located at the top of the rear slope.
So after great difficulty and off camera to save my embarrassment
I’ve finally managed to make my way up onto the engine deck of the M10.
This brings us straight to the travel lock.
The external one, there is an internal one as well.
Or since this is a British vehicle, I guess the gun crutch , it’s the same thing.
It’s like fume extractors, bore evacuator, trunk, boot and so on.
I confuse the heck out of people over here with my Englishisms. Anyway the problem with the M10 in movement
was that there was an issue with the gun,
basically bouncing around, even with the internal travel lock.
As a result it was pretty much mandated that if you were moving at all,
unless you really expect contact around the corner,
spin the turret over the rear, use the travel lock. Now the problem with this is that this is a purely manual traverse turret.
And you can imagine how much fun you would have had
trying to crank the turret around every time,
just because you thought you had to go somewhere. Other features up on here, firstly you can also see the
difference between a diesel powered M10 and the petrol one.
We already mentioned the exhaust, the other one is the engine deck.
The ford V8 has slightly larger grills,
but similar enough the diesel ones fold up and outwards. On the outside you can see that there are
3 ports per side for diesel, oil and water. The engines themselves, it is a general motors Model 6046,
they are twin six-cylinder, two-cycle diesels, water cooled of course. Combined total 375 horsepower, 2100 RPM.
Each engine is 425cubic inches.
This would be enough to tootle the vehicle along at 30 mph.
in a sprint.
The sustained speed according to the manual is 25 mph.
The two engines are entirely independent with their own
cooling, fuel, generation systems and so on.
They can be run independently, simply disconnect one by use of the clutch
and you can limp along with the other. The engines were labeled, LC and LA.
LC for the left engine, LA for the right
and all the parts for each engine had that LC or LA identifier.
I’m not entirely sure why,
because you would’ve thought they were fairly identical, but anyway.
Each engine takes 32 quarts of oil.
Add in 24 more quarts for general lubrication systems.
The air cleaners, you can see them between each side
they are of the wet type they each take 21 quarts. The power train 38 gallons, yes gallons of lubricants.
And finally the water cooling system is 15 gallons each,
that’s quite a substantial amount of POL you got to keep track of there. POL is Petroleum, Oil and Lubricants.
Also known as Class 3 in today’s army.
Finally for fuel there’s an upper 69 gallon tank on each side,
a 14½ lower on each side creating a grand total of 167 US gallons.
This gave the vehicle a cruising range of about 140 miles.
Other thing while I’m up here I’ll just mention the counter weights.
Initially the first vehicles had the grousers for the tracks mounted on them.
The vehicles were equipped with 26 grousers, 10 for each track and 6 spares.
However the turret was out of balance,
they had to add wedge counter weights,
the grousers were then moved to the hull sides. The later model counter weights are these duck bill type,
they’re a little bit longer, they extend out further,
but they do add a little bit of space for some stowage. There is a two shot external fire extinguisher handle
located on the left rear of the engine deck. While I’m on the counter weight you’ll see a number
of these little sticks around the ring of the turret.
You simply put them all up and you attach a canvas cover,
it gives you a little bit of overhead protection against the elements.
So now we’ve moved into the turret
and I’m just going to leave you with this image as we break for Part 2.