I've recently found out some interesting information about UK OOB007 Weapon 038 17 Pounder Gun.
Normally, I wouldn't comment on it; because there's a risk of the subject devolving into everyone advocating for their own specific nationality (as can be seen in the World of Tanks / War Thunder boards); and I do like the SPCAMO approach of using generic data wherever possible; because it "normalizes" everything to the same baseline and represents a level of abstraction in simulating a very messy business called war.
But in this case, the discrepancy is large enough, I think, to merit discussion.
Recently (I don't know when exactly), the Canadian government finished a 10 year project to digitize scores of microfilm reels and place them online.
https://heritage.canadiana.ca/view/o...2/4878?r=0&s=5
On 24 March 1945, the War Office in Whitehall, in a memorandum issued to every major British Formation (21AG, 15AG, AFHQ, CINC Middle East, India, PAIC, ALFSEA), said:
Both trials and operational experience have shown that 17-pr D.S. Shot is inaccurate. As a result of further accuracy trials with a mixture of APCBC and DS shot, it has been found that DS shot leaves a deposit in the bore and when this deposit has accumulated sufficiently the accuracy of subsequent rounds is seriously affected. After as few as 15 DS rounds the accuracy with APCBC may become appreciably worse than that with D.S.
...
All 17-pr guns which have fired DS shot must therefore be regarded as suspect as regards accuracy.
They suggested limiting the issuance of APDS shot to specific guns in a battery to minimize the issue; and that "further trials are being carried out....you will be notified of the conclusions from these trials as soon as possible."
https://heritage.canadiana.ca/view/o...2/4876?r=0&s=5
Several months later, on 19 May 1945, Whitehall issued a followup memorandum afer trials, and basically said:
The basic accuracy of the 17 pounder was:
APCBC shot average 90% zone was 4.3 ft diameter at 1000yds
DS Shot average 90% zone was 8.2 ft diameter at 1000 yds
Essentially, the 90% zone is just that -- the area in which 90% of shot will be expected to pass through.
"The amount of degradation varies from gun to gun, but it was found that after firing only 10 rounds of D.S. shot the 90% zone in a certain gun had increased by 9.7-ft. Thus, if the initial accuracy of this gun was as given in para 2, the 90% zone to be expected with APCBC after firing the 10 rounds of DS would be 14-ft."
They found:
Provided that the fouling by DS is not allowed to progress too far it can be removed by successive rounds of APCBC. The fouling caused by 5 succesive rounds of DS shot may be expected to be removed by the next 10 APCBC rounds. Accuracy will not therefore be endangered by firing odd rounds of DS shot provided that the majority of the shooting is done with APCBC.
There was also apparently firing trials done in the Summer of 1944 with two Fireflies against a target roughly the size of a Panther turret and issued in WO 291/1263 and WO 165/135, both dated 22 September 1944 and mentioned by Nick Moran in the Chieftain's hatch:
https://worldoftanks.com/en/news/chi...armour-part-1/
400 yds
APC hit 90.5%
APDS hit 56.6%
600 yds
APC hit 73.0%
APDS hit 34.2%
800 yds
APC hit 57.3%
APDS hit 21.9%
1000 yds
APC hit 45.3%
APDS hit 14.9%
1500 yds
APC hit 25.4%
APDS hit 7.1%
As I mentioned earlier, the discrepancy is big enough I think, to warrant discussion, because 17 pdr APDS shot is powerful enough (28 pen) vs normal APCBC (17 pen) that without lowering accuracy to compensate, it makes the weapon artificially powerful.