APDS questions

[William Clodius]

In discussions of the 17pdr APDS ammunition there are numerous
references to the US tests in mid-1944 that indicated that the 17 pdr
APDS accuracy deteriorated significantly beyond about 500 yds (meters).
I am under the impression that the British were not as unhappy with APDS
perfromance as the tests would suggest. Is my impression correct? I
would have expected that 6 pdr APDS would have similar instability on
separation issues, but I have not found any discussion of 6 pdr APDS
performance. IS it known wether it had similar accuracy problems?

[Rich]

Post by William Clodius
In discussions of the 17pdr APDS ammunition there are numerous
references to the US tests in mid-1944 that indicated that the 17 pdr
APDS accuracy deteriorated significantly beyond about 500 yds (meters).
I am under the impression that the British were not as unhappy with APDS
perfromance as the tests would suggest. Is my impression correct? I
would have expected that 6 pdr APDS would have similar instability on
separation issues, but I have not found any discussion of 6 pdr APDS
performance. IS it known wether it had similar accuracy problems?

William,

It was the tests at Isigny in August 1944 that are the basis for both
sides of that evaluation of 17-pdr APDS. The rounds used there proved
grossly inaccurate. However, while US Army Ordnance evaluated that result
as expected, based upon the results of its own experience with APDS
development over the previous two years, British Ordnance attributed
the fault to a bad ammunition lot and decided to go ahead with the
issue of it to units.

The thing is, the US Ordnance assessment was correct - incomplete
sabot separation, aluminum residues in the tube from firing,
misalignment of sabots, and other factors were the problem and
were not solved until the 1950s. Yes, 6-pdr APDS had similar
problems. However, the decision to go ahead and issue it was
also correct, since they sensibly recommended limiting the
ranges they be fired at to around 500 yards; most of the accuracy
issues were only a factor at ranges over 800 yards. Then, given
the average engagement range was under 800 yards, then the result
was APDS was used generally with effectiveness. The inaccuracy of
6-pdr APDS never became an issue since it was a weapon system
typically only used at fairly short ranges anyway.

Odder still, US Ordnance identified the solution for improving
76mm/3-inch HVAP in the same tests, but the recommendation of the
officers at the test were not carried through. The inertia against
certain changes in US Ordnance was (and still is) immense. The
recommendation to increase the propellent load in the 76mm
cartridge while retaining the HVAP projectile as a standard
AP round went nowhere...until 1946 when Aberdeen tests demonstrated
it was the correct solution (along with specially heat-treated
monobloc AP rounds) for use against heavy armor and was perfectly
practical in the existing 76mm gun.

Cheers!

[William Clodius]

<sni> Yes, 6-pdr APDS had similar
problems. However, the decision to go ahead and issue it was
also correct, since they sensibly recommended limiting the
ranges they be fired at to around 500 yards; most of the accuracy
issues were only a factor at ranges over 800 yards. Then, given
the average engagement range was under 800 yards, then the result
was APDS was used generally with effectiveness. <snip>

I was under the impression that while average engagement range varied
with theatre and even terrain within the theatre, for both Italy and NWE
the average range was over 800 yards, albeit not much over 800. Also
whiatever the "average" range I was under the impression that the
Sherman Fireflies were typically placed near the rear of the British
task forces, to make them less prominent targets, which would place them
50-100 yards further back. I have, however, read little about how the
other 17pdrs/6 pdrs were used.

[Rich]

Post by William Clodius
I was under the impression that while average engagement range varied
with theatre and even terrain within the theatre, for both Italy and NWE
the average range was over 800 yards, albeit not much over 800. Also
whiatever the "average" range I was under the impression that the
Sherman Fireflies were typically placed near the rear of the British
task forces, to make them less prominent targets, which would place them
50-100 yards further back. I have, however, read little about how the
other 17pdrs/6 pdrs were used.

No, according to "Survey of Allied Tank Casualties" the average range
for NWE was 800 yards, 900 yards for Africa, and 350 yards for Italy and
Sicily. Of course that was for its engagement set, but it was a robust
study with 800 samples for NWE, 100 for North Africa, and 60 for Sicily
and Italy. Further, the sample for NWE did actually include African and
Italian losses, so it seems likely the overall "average" is likely closer
to 800 yards.

As I understand it reading the RAC notes, the Sherman 17-pdr was held
back more for a control and protection rather than a range issue, but
you also need to consider that most engagements would be with the more
common APC rather than the APDS. While APDS was common issue with
British 6-pdr by 6 June, it was only issued on any significant scale
for 17-pdr after September.

As far as 6-pdr goes, most were towed with infantry battalions or
with the 6-pdr troop of the AT regiment, which was normally assigned
to the infantry brigade. They were first line of defense for the
infantry battalion, so were on the front line, but usually in defilade
designed - and intended - to enable flank shots for maximum effect.

Cheers!