Plate testing .30-06


#1

I got a couple of rounds from this very box and a photo of the box itself (alas,only photo) in Williamsport. Question: Why are there 2 different distances mentioned on the box? How is testing conducted? Is there a certain standard distance for testing? Surely one can’t predict the distance between the soldier and the target in the battlefield.


#2

Vlad–This ammunition was not issued to the soldier in the field. It is not the same as regular AP. It was used to test the puncture resistance of Armour Plate during the manufacture and development in the factory. So, the Armour Plate to be tested would be set up at the two distances mentioned. To be able to compare one type of Armour Plate against another, the velocity of the bullet had to be controlled accurately.


#3

Ok, I thought we were testing how good a lot of AP is. Then we are testing the thickness of a plate of metal. Shouldn’t the thickness of a sheet of metal be some integral part of steel manufacturing? Or easier way, like drilling a hole, to measure it?


#4

Armour plate is made from alloy steel. Its strength, and resistance to penetration, will depend upon the alloying elements (percentage mix if you like), heat treatment and work hardening during rolling. So, a simple measurement of thickness will not test its suitability.

These plate tests are carried out on all thicknesses and types of armour plate, using bigger calibres and varying velocities. The UK used variations of 20x110mm Hispano (with a special short projectile), 2 Pounder, 6 Pounder, 17 Pounder, 20 Pounder and various APFSDS rounds for plate testing. For these larger calibres the rounds were individually hand loaded at the test range and the velocity and penetration result accurately measured for each shot. If the shot didn’t quite penetrate another round was loaded to a slightly higher velocity and the test repeated until a clear penetration resulted. The requirement was to find the shot which just did the job and use this data to compare the strength and quality of similar plate samples.

gravelbelly.


#5

You need to know the velocity to calculate the KE. 1830 fps at 150ft appears to me to be lower than service velocity but that is not important. It is only used to test. You will probably find there are similar test rounds with a range of different velocities so that the penetration can be assessed across a range energy levels without having to vary the distance.


#6

Vince/Vlad
The velocity IS reduced, IIRC the “standard” loading is in the 2700fps @ 150’ (30yards) range.
Using a lower velocity allows them to test either the bullets or the armor plate at shorter ranges. IE: they could test at 100yd and see the same penetration results as “standard” ammo at 600 yd (I don’t have a ballistics program handy, to calculate the actual range at which the velocity would be down to 1750fps).


#7

There were plate test cartridges loaded to different velocities than the ones shown. The actual velocities depended on the materials being tested (steel, plexi-glass, laminates, etc).

The ones shown were loaded to a muzzle velocity of 2000 fps +/-. This is the equivilent of a standard Cal .30 AP at 375 yards. Or, 450 yards (1830 fps) and 550 yards (1750 fps). With simple math it’s possible to determine velocities at different yardages.

Vlad, if your cartridges are correct, they should have a silver over black tip.

Ray


#8

I have a few dates of this loading but I only know the lot number of one of them (FAX 30-280) that I bought from Jim Tillinghast years ago. It is interesting in that only a single velocity is noted for each lot. There are at least 9 lots that run from 1800 f/s to 2200 f/s in 50 f/s increments.
Diebold Safe and Lock Co. (order E5186) must have made or at least tested armor plate at the time.

Lot F.A. X 30-279 Velocity 1800 f/s at 300 feet
Lot F.A. X 30-280 Velocity 1850 f/s at 300 feet
Lot F.A. X 30-281 Velocity 1900 f/s at 300 feet
Lot F.A. X 30-282 Velocity 1950 f/s at 300 feet
Lot F.A. X 30-283 Velocity 2000 f/s at 300 feet
Lot F.A. X 30-285 Velocity 2050 f/s at 300 feet
Lot F.A. X 30-287 Velocity 2100 f/s at 300 feet
Lot F.A. X 30-288 Velocity 2150 f/s at 300 feet
Lot F.A. X 30-289 Velocity 2200 f/s at 300 feet


#9

Just picked up a box of .50 M2 AP bullets for Plate Testing, just projectiles no loaded cases. This does not have velocities mentioned on box or a date, but it does say:
Hardness-Rockwell C scale 61 to 66 inclusive
Use only in loading ammunition for testing armor plate
Frankford Arsenal
The tips are silver over black band, but in Jean Huon book “Military Rifle and Machine Gun Cart” he mentions the tips with a black tip over silver band. I’m hoping its silver/black. Looked on internet, found auction from 2008 that had a loaded plate test .50 that had silver over black. Says it was for the armor advancement test program pre ww2, headstamp FA/ 41, live round that sold for $40. That date matches your box too!
Why doesn’t the 30 cal box mention Rockwell hardness if its for plate testing? I’ve heard its really RHC 63 (HV 785) for the .30 cal?
Isn’t 61 to 66 a pretty big range, shouldn’t the .50 cal box be more specific? wolfgang


#10

WGG
5 points on the Rockwell scale is not a real large spread. The high price calibration blocks have a 3 point spread once you get into the 60’s. Considering that (on the older style Rockwell machines) 3 experienced operators using the same machine, block & diamond will get 3 distinctly different readings, due to the slight differences in how they operate the machine.


#11

Wolfgang – here are a couple specimens of the .50 Cal AP-Plate Testing rounds but I have no additional information on either one. Good example of if you don’t have the box or label, you really don’t know what you have!


#12

I can confirm the lot numbers PBUTLER mentions for the Diebold tests.
In addition to that, I am aware of following tests for the Universal Cyclops stel Corp.
Lot F.A. X30-58 2730 feet/second at 53 feet order 6506 & 6520
Lot F.A. X30-272 2300 feet/second at 300 feet order 6060

Furthermore there are some pictures in Marcello’s book.
A contract ? for E.E.M.M. No. 28 FY44 (anybody an idea what that means ?)
FA X30-871 2055 feet at 78 feet
FA X30-872 2255 feet at 78 feet
FA X30-873 2455 feet at 78 feet

Also Marcello shows pictures of boxes with lot numbers between X30-300 and 400 but these are all without
any contract names.

Below is an earlier plate testing box from my collection. This one uses the M1922 bullet

If anybody has more info on lot numbers and velocities or has boxes to trade, pls send me a mail.

cheers
René