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British APDS tank ammunition

SG500

SG500

Well-Known Member
Premium Member
I was sorting out a shelf of stuff today and thought a group photo was needed of the British APDS tank ammunition. I realise the one one the right isn't APDS but thought it fitted in as its cored.

From left to right:

120mm as used on the Conqueror. Separate charge and projectile.
120mm Separate combustible rigid charge bag and projectile
110mm. Experimental semi combustible case with brass base stub. This comes as a fixed round.
105mm. Fixed round
20 pounder. Fixed round
17 pounder/77mm. Fixed round
17 pounder/77mm short case as used in the Comet. Fixed round
6pr7cwt. Fixed round
2 pounder littlejohn Mk 2 fixed round

ALL INERT

Dave.

IMG_1206.jpg
 
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SABOT DROOL FORMING! Great pic of some beautiful specimens, Dave! Wowzers!


Jason
 
Really nice family shot Dave, much appreciated.
Oh and lovely condition rounds to boot
Rich
 
When you compare the size of the 17pdr case and therefore volume and correspondingly the engergy given to the projectile, and compare with other 70mm-90mm rounds of the same period, you can almost visually see why the 17pdr was such an effective anti tank weapon. Then again when you compare the 17pdr to the 77mm it's amazing the 77mm penetrative performance came anywhere close (APDS or APCBC). It's positively tiny in comparison, yet delivers 85-95% of the performance. (I appreciate there are other variables than the volume of propellant)

Now compare to the volume of the conqueror case....!! good lord! ;-)
 
Interestingly, muzzle energy of 17pr versus 77mm firing APCBC is 31% higher and 35% higher on APDS. You would expect a greater difference in penetration.
 
I think that some of the figures often quoted for 77mm and 17 pdr penetration are incorrect, but they've been copied so many times they are regarded as true!

For example, the RAC Tank Museum's Fire & Movement booklet quotes penetration at 100 yards/30 degrees for APCBC as 110mm for the 77mm and 118mm for the 17 pdr. This makes no sense given the difference in power. Many years ago I researched this and dug out various other sources. As a result of which, I found that the true figures seem to be around 100mm and 134mm respectively. Figures for APDS are similarly distorted (F&M gives 165mm for the 77mm, 170mm for the 17 pdr!). I can only assume that the performance of the two guns in F&M was measured under different conditions, e.g. using different qualities of armour.

By comparison, figures in F&M for the German APCBC equivalents seem much more realistic: the 75mm L/48 tank gun (which is slightly less powerful than the 77mm) penetrates 90mm, the long 75mm L/70 in the Panther tank (marginally more powerful than the 17 pdr) is credited with 141mm.
 
Hi Dave,
please excuse my ignorance,these are way out of my comfort zone with what I collect, but how does the 2 pdr chamber in the breech with the projectile being a lot wider than the neck of the case?...

Atb
Tony
 
Tony Williams said:
I think that some of the figures often quoted for 77mm and 17 pdr penetration are incorrect, but they've been copied so many times they are regarded as true!

For example, the RAC Tank Museum's Fire & Movement booklet quotes penetration at 100 yards/30 degrees for APCBC as 110mm for the 77mm and 118mm for the 17 pdr. This makes no sense given the difference in power. Many years ago I researched this and dug out various other sources. As a result of which, I found that the true figures seem to be around 100mm and 134mm respectively. Figures for APDS are similarly distorted (F&M gives 165mm for the 77mm, 170mm for the 17 pdr!). I can only assume that the performance of the two guns in F&M was measured under different conditions, e.g. using different qualities of armour.
Click to expand...

Hi Tony - thanks for stating this - I often wondered about it too.
The muzzle velocities would confirm this beyond doubt.

I have the muzzle velocity of the 17pdr at 3950 fps. I can't find any listed for the 77mm APDS... anybody have it?

For their APCBC rounds I have M.V. of the 77mm (2575fps) being about 88% that of the 17pdr. (2900fps), with a resultant decline in penetration to about 84% of the 17pdr. I suspect a similar drop for APDS.


PS - thanks for your web site!
 
smle2009 said:
Hi Dave,
please excuse my ignorance,these are way out of my comfort zone with what I collect, but how does the 2 pdr chamber in the breech with the projectile being a lot wider than the neck of the case?...

Atb
Tony
Click to expand...

Hi, on this specimen the forward flange is slightly narrower diameter than the rear flange which is itself only just wider than the the case neck, no wider than you would expect from a regular driving band. This one actually sits with a small part of the rear flange protruding from the case like a regular driving band would, the more common version of the Mk 2 littlejohn has a rear flange which sits entirely within the case and the crimping would enclose the rear flange. So to answer the question, the projectile isn't wider than the case neck.
Hope that helps.
Dave.
 
Thanks Dave...in the photo the rear flange looks about the same diameter as the case shoulder,hence my dumb question.

Tony
 
Here is the pot of a Shot 20pr APDS Mk 3/1
 

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  • Shot 20pr APDS poy-2.jpg
    Shot 20pr APDS poy-2.jpg
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tankbarrell said:
3400 fps for APDS, 2575 for APCBC.
Fire & Movement lists the 77mm APDS as 3,675 fps
Click to expand...

So the 2575 number is about 86% of 17pdr MV,
and the 3675 number is about 93% of 17pdr MV,
while the APCBC was about 88%. Both numbers sound reasonable.
I don't have striking velocity curves for APDS - so using the curve for 76mm HVAP, using the average of those 2 numbers, I would expect the penetration of the Comet at point blank range to be about the same as a 17 pounder fired from about 600 yards further back.
That translates into a about a 30mm difference in penetration given the same range.
Hey! That matches your numbers Tony - "I found that the true figures seem to be around 100mm and 134mm respectively".
I think all the war gamers (myself included) need to redo their 77mm APDS penetration tables!
 
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