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From various British War Office (WO) documents and I don't have copies of the originals. A few are from images of photos of the original printed pages.
1. WO 291/238 AORG Report No.256 "The Importance of Gun Dispersion in A.P. Shooting"
(Assumed to be using 90%)
6pdr APCBC dispersion at 1000yds 5.2mins - tangent (5.2/60) x 1000 / 2.44 = 0.619.
75mm Mk.V APCBC dispersion at 1000yds 3.0mins - tangent (3/60) x 1000 / 2.44 = 0.357.
17pdr APCBC dispersion at 1000yds 5.2mins - tangent (5.2/60) x 1000 / 2.44 = 0.619.
17pdr APDS dispersion at 1000yds 12.0mins - tangent (12/60) x 1000 / 2.44 = 1.43.
Covert British 90% zone to German style 50% zone divide by 2.4387 ~ 2.44.
Note- 17pdr dispersion is assumed to include fouling from aluminum residue by using APDS rounds.
Probability Conversions link
2. AORG Memo No. 514: 90% zone Accumulated From 31 10 shot tests 1944
1000 yds 90% zone 50% zone @ 1000
17 pdr Mk1 AP, APC:line/vert 3.9min / 4.2min - tangent (a/60) x 1000/2.44 = 0.465 / 0.5
17 pdr Mk1 APCBC: line/vert 3.3min / 3.6min - tangent (a/60) x 1000/2.44 = 0.393 / 0.429
3. Weapon Research Committee: accuracy of anti-tank guns and rigidity of gun barrels", 1948 [PRO piece number WO 195/10134],
Gun Ammunition m.v. (f.p.s.) Ave m.d. of strike
6-pr 7 cwt APCBC 2725 0.9' - tangent (0.9/60) x 1000 x1.69 = 0.442 yd
Mks 4 and 5 APDS 3850 2.3' - tangent (2.3/60) x 1000 x1.69 = 1.13 yd
17-pr APCBC 2900 0.8' - tangent (0.8/60) x 1000 x1.69 = 0.393 yd
Mks 1-5 and 7 APDS 3950 2.0' - tangent (2.0/60) x 1000 x1.69 = 0.98 yd
77mm APCBC 2575 0.7' - tangent (0.7/60) x 1000 x1.69 = 0.344 yd
APDS 3400 1.2' - tangent (1.2/60) x 1000 x1.69 = 0.59 yd
There are a number of documents on shooting percentages. This will need the Ballistic Accuracy calculator to model the dispersion.
4. WO 291/238 AORG Report No.256 "The Importance of Gun Dispersion in A.P. Shooting"
Theoretical chances of a hit on a 2-ft high target representing a hull-down tank at 1,000 yards.
Gun ammo 2nd shot calc. dispersion
6-pdr HV 38% 0.76 yd
77mm APCBC 56% 0.55 yd
17 pdr APDS 17% 1.29 yd
Standard range error is 250 yd at 1000 or 25% s.d. or 19.95% mean error.
Gun First shot calc. dispersion
77mm 11% 0.64 yd
17 pdr 15% 0.47 yd
5. WO 291/751 AORG Memo No.427, 24th Nov 1944, "Comparative Dispersion of Tank Guns"
Probability of a hit when firing for effect on a target 2' high by 5' wide (M.P.I. assumed on centre of target) at
500yds 800yds 1000yds Calc. From dispersion of:
Churchill IV 6pdr APCBC 150rnds 74% 73% 62% 0.5 yd.
Churchill IV 6pdr APDS 90rnds 74% 50% 37% 0.76 yd
Sherman 17pdr APC 100rnds 88% 66% 52% 0.59 yd
Sherman 17pdr APDS 40rnds 42% 21% 14% 1.44 yd
Comet 77mm APC 40rnds 98% 86% 76% 0.38 yd
6. WO 291/1263, Firing Trials, 17pdr Sherman
"Table VI has been constructed which shows the probability of a hit on a target 5' wide by 2' high
(representing a Panther turret) at various ranges using both types of round."
Range (yards) APC % AP/DS %
1000 45.3 [0.335 yd] 14.9 [0.7 yd] (assuming 17% mean ranging error)
7. WO 291/180, Accuracy of anti-tank gunnery
Ranges in yards, target assumed to be Pz VI size.
Probability (%) of hitting static hull-down target after first round:
Gun 500 1000
6 pdr 85 43 - 0.7 yds
17 pdr 88 51 - 0.6 yds
8. Table "D." 28 Dec. '44 No. Q. 2.908
Range At Which There is a 50 Per Cent. Chance of Obtaining Hits. Hulldown target = 2' x 5'
Hulldown Q.F. 6-pr 7 cwt. Q.F. 17-pr
APCBC DS APCBC DS
First shot 500 yds [0.84] 500 yds [1.06] 600 yds [0.28] 500 yds[1.15]
Subsequent hits 800 yds.[0.77] 600 yds [1.02] 900 yds[0.68] 600 yds [1.02]
(Note. This also includes jump and throw off.)
The British seem to think the average mean range estimation error with a telescope sight was 20-25%.
Nick Moran, the Chieftain, found some documents of dispersion tests at Aberdeen Proving Ground. link
9. The US tested the 17 pdr to determine the dispersion of APCBC and APDS. They tested at 500 yds., 1000 yds, and 2000 yds. They found that mean dispersion at 1000 yds deflection: .233 mils, elevation: .219 mils. Now this works out to a 50% zone of .387 yds / .364 yds at 1000 yds. Now this would be great except they moved the center of the target to the center of the spread. This means that jump and throw-off have to be included in the calculation to compare it to German and Russian deflection numbers. To do this we have to look ahead one page to the Post War reports
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