U.S. Army 1944 Firing Test No.1

Report on Comparative Firing Program Witnessed at Shoeburyness, Essex, 23 May 1944 by U.S. Army Headquarters ETO representatives.

ARMORED FIGHTING VEHICLES & WEAPONS SECTION

APO 887

319.1 – 24 May 1944

MEMORANDUM TO: Executive Officer, AFV&W Section, Hq., ETOUSA.

SUBJECT: Report on Comparative Firing Program Witnessed at Shoeburyness, Essex, 23 May 1944.

1. Introduction: Comparative firing tests between 76mm (M1), 17pdr (Mk.I), 90mm (M1), and 75mm (Mk.V), guns were conducted against rolled homogeneous armour plate at 30º obliquity with service, APC(BC), ammunitions. The 17pdr fired solid shot, the 90mm and 76mm guns fired shot loaded with a base charge of Explosive “D”, and the 75mm fired both inert loaded and Explosive “D” loaded shot.

2. Program:

a. Phase I – The 17pdr, 90mm and 76mm were fired at 120mm homo plates (@ 30º) at 800, 400, and 100 yards to determine their comparative armor penetration characteristics.

b. Phase II – The 17pdr, 90mm and 76mm were fired at 100mm homo plate (@ 30º) backed up by a vertical 100mm plate at 500 yards to determine the relative damage caused behind [the first] plate.

c. Phase III – 75mm APC M61, inert loaded and Explosive “D” loaded, was fired at a 20mm homo plate spaced 6 inches [152mm] in front of a 50mm face hardened (1) plate at 30º obliquity at 500 yards to determine the limitations of base charge shot as opposed to solid shot in the attack of spaced armor.

3. Results – (See Inclosure No.1) The firing tests were too brief to support any positive conclusions, however the tests indicated that:

a. At close ranges the 17pdr gun has decidedly superior armor penetrating characteristics as compared with the other guns and ammunition fired.

b. Phase II – The instantaneous detonation of the relatively large base charge of the 90mm, Shell, APC M82 adversely effects the armor penetration characteristics of this ammunition against heavy armor plate at 30º obliquity. As a result, under certain combinations of range and armor thickness, it can be out-performed by inert loaded 76mm APC M62.

c. Phase III – It is possible to defeat the attack of 75mm APC M61, Explosive “D” loaded, at certain obliquities and ranges with a 20mm homo plate spaced 6 inches in front of a 50mm face hardened1 plate. This deficiency is further supported by extensive firing tests conducted under Ordnance Board Proceedings No. 26,495. (See Inclosure No.2).

4. Addendum – Blast effect of 76mm gun M1, in Medium Tank, M4A1, during firing tests. A total of four (4) rounds were observed from the tank commander’s position. Blast obscuration timed in observing a target at 1000 yards varied between 3.1 and 5.8 seconds. It is not believed that tracer could have been picked up by a tank commander with field glasses under 1500 yards. Firing was conducted in a 5 to 10 mile, 12 o’clock wind, in a grassy field. There was absolutely no dust encountered. All obscuration resulted from muzzle smoke.

RL D. BRENT, II,

Captain, Cavalry

2 Incls:

Incl 1 – Record of Firing.

Incl 2 – Summary of Ord Bd Proceedings 26495

Notes:

(1) The original wording of the report states “homo” in type but this has been crossed out and “face hardened” written in in hand writing.

Inclosure No.1

RECORD OF COMPARATIVE FIRING TEST

Shoeburyness – 23 May 1944

Rolled Homo @ 30º ; Service Velocity Ammunition

ROUND AMMUNITION*** RANGE ARMOUR
THICKNESS
BDF
FUNCT-
IONING
RESULTS**
PHASE I
1 90mm Shell, APC M82 800 yds 120mm yes PP – Depth 3″, Bulge 3/8″
2 17pdr APCBC 800 yds 120mm PTP
3 & 4* 90mm Shell, APC M82 400 yds 120mm yes PP – Depth 4″, Bulge 1½”
5 76mm Shell, APC M62 400 yds 120mm no PP – Depth 21/8″, Bulge 1/8″
6 90mm Shell, APC M82 100 yds 120mm yes PP – Depth 4″, Bulge ¾”
7 76mm Shell, APC M62 100 yds 120mm no PP – Depth 2¼”, Bulge 1/8″
PHASE II
8 17pdr APCBC 500 yds 100mm PTP – Excellent Spall Effect
9 90mm Shell, APC M82 500 yds 100mm yes PP – Depth 33/8″, Bulge 7/8″
10 76mm Shell, APC M62 500 yds 100mm no PTP
11 76mm Shell, APC M62 500 yds 100mm no PTP
PHASE III
12 75mm Shot, APC M61 500 yds 20mm
6″ in front
of 50mm
FH1
PTP
13 75mm Shot, APC M61 500 yds PTP
14 75mm Shell, APC M61 500 yds no PTP
15 75mm Shell, APC M61 500 yds yes (see note 2)

* Successive rounds, point of impact one to two inches apart.

** Results:
PTP = Projectile passes through plate.
CP = Complete Penetration – projectile failed to pass through plate, but light visible through hole or crack in plate.
PP = Partial Penetration – failure to make crack or hole in plate through which light3 is visible.

*** Lot Numbers:
90mm Shell APC M82 – OOP 6
76mm Shell APC M62 – OOP-1-2
75mm Shot APC M61 – 12-22415-26 KOP
75mm Shell APC M61 – GR-3-4

Notes:

(1) FH = Face Hardened, the FH has been added in hand writing.
(2) Result for this round reads: “Projectile passed through first plate and base charge detonated between plates – Only spall and fragmentation effect on surface of second plate”.
(3) The word ‘light’ has been added in hand writing.

Inclosure No.2

ARMORED FIGHTING VEHICLES & WEAPONS SECTION

APO 887

SUMMARY OF CONCLUSIONS FROM ORDNANCE BOARD PROCEEDINGS No. 26495

1. 75mm APC M61 Inert loaded and Explosive “D” loaded have similar maximum perforative performances against single homogeneous plate.

2. Against a spaced plate assembly consisting of 20mm homo4 plate in front of 50mm FH plate, the shell failed at all velocities up to the velocity of the gun. The same shell, but with empty fuse succeeded against this target at velocities above 1780 f/s (equivalent to a range of about 850 yards with a MV of 2050 f/s). The failure of the filled and fused shell must be attributed to fuse action and detonation between the plates.

3. Against 70mm homo plate at normal or 60mm and thinner plates at 30º the shell was as successful as shot and gave detonations at distances of up to 20 feet in rear of the target5.

4. The effect of 5mm and 8mm skirting plate in front of 30mm homo plate did not affect the performance and successful functioning of the fuse6.

Notes:

(4) This possibly is a typo and should have been altered to Face Hardened – it is unclear if both plates were face-hardened, or just the second (50mm thick ) one.
(5) 70mm plate at 30º is equal to a thickness of 81mm on the horizontal plane. The records of these firings are not included in the documentation.
(6) The records of these firings are not included in the documentation.

CONSOLIDATION OF DATA FROM ORDNANCE BOARD PROCEEDINGS 23114 AND 26594

75mm APCBC M61 – HE filled versus Inert loaded

75mm APCBC M61 - HE filled versus Inert loaded

75mm APCBC M61 - HE filled versus Inert loaded

ETOUSA OUTGOING MESSAGE

ORIGINATOR: ETOUSA.

DATE: 24 May 1944.

ACTION TO: AGWAR.

INFO TO: CG AGF.

TEXT: Recent firing tests indicate twenty mm homo plate spaced six inches from fifty mm FH plate at thirty degree obliquity will defeat service velocity seventy-five mm APC M sixty-one at five hundred yards by functioning base fuze.

(signed Eisenhower)

Also tests witnessed indicated instantaneous functioning of HE filling in ninety mm APC M eighty-two does not permit satisfactory armor penetration performance on one hundred mm homo plate at thirty degrees at five hundred yards.

(Reference ETOUSA cable WL dash two one nine two and British ordnance board proceeding number two six five nine four)

If tests in US indicate above deficiencies cannot be corrected immediately it is requested all seventy-five mm seventy-six mm and ninety mm APC shipped for ETO be inert loaded.

DISTRIBUTION: Ord O, G-3, G-4, FUSAG, SHAEF.

ORIGINATING DIVISION: AFV&W Section.

PRECEDENCE: Routine.

NAME & RANK: W. J. Reardon, Col, Cav, 1039.

This signal was prepared as a result of these tests but not actually sent (possibly because of the potential morale effects if it had leaked out or become public knowledge, or because the tests were not considered adequate for this conclusion to be made).

This information above was supplied to me by Jim O’Neil (Arizona, USA), the original source is declassified documents made available in 1974 and 1988.

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