Is this a shot test

[Justin Pollard]

Hello Dale,

From what I've worked out the steel was test shot before the plate was fitted to the carriers, probably during manufacture whilst the plate was just flat, as I have seen test marks where it would be impossible to do once the hull was welded together.

Regards
Justin.

[Michael R.]

How interesting. This "test shot" business ... is this a country specific quality assurance method?

I am intrigued by the thought that a rifle round was discharged against a hull plate, and the same plate eventually ends up as a portion of an assembled hull. Is this an urban legend or factual?


There are regularly spaced hardness standard testing marks on Canadian light armour plate as well as the more commonly visible and commented on straightening marks. The American owned company responsible for heat treating and straightening 45,000 tons of wartime production Canadian light armour plate stamped their company logo into the plate. Some side plates on Canadian U.C.'s also display a four digit serial number.

As for an assembled Canadian production vehicle showing hardeness testing tool marks attributed to a fired rifle round, or a documentation trail to support the theory, that is quite elusive.

Bob, Justin, can you elaborate?

[rob love]

I think I have to concur with Micheal on this one, unless someone comes up with some other evidence. I think this is an old wives tale.

I have used left over carrier armour as targets at shooting matches. In one case, hundreds of rounds of all calibers were fired at the front armour off a mk1. The Boyes rifle penetrated as to be expected, and one smaller round penetrated through the armour near where the vision slot was (I'll assume that the cutting process for the slit weakened the armour very locally) but other than those, all any of the small arms did was scratch the paint.

I have also noted the dimples on the right side armour to be very evenly laid out. So, as Micheal said, does anybody have documentation as to what exactly the hardness test was?

[Lynn Eades]

Hi. The "test" on Australian, New Zealand and Early British built carriers, leaves an obvious dent in the plate. It is nicely rounded, and I do not believe for 1 second that, it is the result of being shot at by a bullet from a firearm. I do believe it is the result of a mechanical device, something like a spring or air propelled bolt, designed for the purpose. Bob where is your evidence? I dont recall (this is my out) seeing anything like it on Canadian armour.

[Nathan Clark]

I agree with Bob on this one, I believe that the test holes were done with a firearm, most likely with a 303 as Bob suggested. My proof to this theory is the fact that all test holes done on 1824 in particular still have trace elements of lead in the test holes and they are not all unison in size or shape. If they were done with a punch or a rivet gun etc. all the holes would be perfect and unison in shape. I know for a fact that the holes were put in 1824 before construction and are not battle or post-war related because they are mostly in spots that would be impossible to shoot or 'test' once the carrier was assembled. The steel in a LP2a would have been designed to stop rounds up to .303 in calibre so if you were going to test the steel during construction, if would have been quite simple to just discharge a .303 at it and find out wouldn't it?

Nathan

[Michael R.]

Well, I suppose if you expected your carrier to be fired upon by the standard .303BRIT round, it may be reasonable to perform a proof test to that standard. A .303BRIT standard bullet would have a jacket made of a material that encases a lead core. Could one expect the adversary to be equipped and shooting at you with 7.92x57 or perhaps 7.7x58 ? Those rounds would likely be fired from a distance and angle other than what we see in the LP2A. Close range and at right angles would be a worse case scenario. Not to mention 20mm Solothurn ... Quite interesting Nathan. I do not doubt the possibility that a rifle round may have created the mark shown: I am simply intrigued that it enters production.

Why would a factory invest time and material to produce an armoured vehicle without having knowledge ahead of time that the material meets standard?

It is a common practice to test assorted armour under simulated field conditions on post production items, in particular at set periods of time during service life. Once the armour has been struck by a round, it is not deemed appropriate to return the item to stock for service issue.


Here is an image showing an example of a heat treated Canadian Universal Carrier side plate, displaying what I believe is the hardness test dimple,(update, not from a bullet strike) along with strike marks left from the straightening process, and the control or registration number of the production plate. The number is not related to the lower hull number, upper hull number, serial number or WD number. On the sample shown, the opposite side plate of the Carrier has a non-sequential number.


There are numerous wartime examples showing Canadian Universal Carrier armour was defeated by enemy small arms fire. Here is an image of a captured Canadian made MKI* that has gone through the retrofit program to the MKII UCW standard. You can see the side plate has been struck at an acute angle and defeated. June, 1944, France. Ignore the red circles, they identify the deep wading plate pads over the MKI* folding armour.

As a side note, you can see this Carrier being driven by the adversary, as it is brought along side of a Sherman. See minute 7:49 in: http://www.youtube.com/watch?v=Dpb9_YS3CzE

[Hanno Spoelstra]

Originally Posted by Michael R.

It is a common practice to test assorted armour under simulated field conditions on post production items, in particular at set periods of time during service life. Once the armour has been struck by a round, it is not deemed appropriate to return the item to stock for service issue.

Here is an image showing an example of a heat treated Canadian Universal Carrier side plate, displaying what I believe is the hardness test dimple, along with strike marks left from the straightening process, and the control or registration number of the production plate. The number is not related to the lower hull number, upper hull number, serial number or WD number. On the sample shown, the opposite side plate of the Carrier has a non-sequential number.

I agree, the dimple is a sign of the hardness testing method, most likely the Brinell Hardness Test:

Brinell hardness is determined by forcing a hard steel or carbide sphere of a specified diameter under a specified load into the surface of a material and measuring the diameter of the indentation left after the test.The Brinell hardness number, or simply the Brinell number, is obtained by dividing the load used, in kilograms, by the actual surface area of the indentation, in square millimeters.The result is a pressure measurement, but the units are rarely stated.
(...)
The Brinell hardness test was one of the most widely used hardness tests during World War II. For measuring armour plate hardness the test is usually conducted by pressing a tungsten carbide sphere 10mm in diameter into the test surface for 10 seconds with a load of 3,000kg, then measuring the diameter of the resulting depression.

The number most likely is the lot or batch number of the batch of plates going through the hardening process at the same time. Typically only a few samples of a batch are tested, and if the samples fail the test the whole batch is rejected or reworked. The batch number is used to ID the plates that need to be rejected or reworked.

Testing each plate by firing a bullet sounds like a laborious, dangerous, costly process with unreliable results as there is too much variation. To rule out variation in hardness testing, men like Brinell, Rockwell and Vickers developed standardized tests with reliable measured outcomes.

For what's my €0,02 worth, anyway.
Hanno

[Paul Dutton]

Originally Posted by Michael R.

Well, I suppose if you expected your carrier to be fired upon by the standard .303BRIT round, it may be reasonable to perform a proof test to that standard. A .303BRIT standard bullet would have a jacket made of a material that encases a lead core. Could one expect the adversary to be equipped and shooting at you with 7.92x57 or perhaps 7.7x58 ? Those rounds would likely be fired from a distance and angle other than what we see in the LP2A. Close range and at right angles would be a worse case scenario. Not to mention 20mm Solothurn ... Quite interesting Nathan. I do not doubt the possibility that a rifle round may have created the mark shown: I am simply intrigued that it enters production.

Why would a factory invest time and material to produce an armoured vehicle without having knowledge ahead of time that the material meets standard?

It is a common practice to test assorted armour under simulated field conditions on post production items, in particular at set periods of time during service life. Once the armour has been struck by a round, it is not deemed appropriate to return the item to stock for service issue.


Here is an image showing an example of a heat treated Canadian Universal Carrier side plate, displaying what I believe is the hardness test dimple, along with strike marks left from the straightening process, and the control or registration number of the production plate. The number is not related to the lower hull number, upper hull number, serial number or WD number. On the sample shown, the opposite side plate of the Carrier has a non-sequential number.


There are numerous wartime examples showing Canadian Universal Carrier armour was defeated by enemy small arms fire. Here is an image of a captured Canadian made MKI* that has gone through the retrofit program to the MKII UCW standard. You can see the side plate has been struck at an acute angle and defeated. June, 1944, France. Ignore the red circles, they identify the deep wading plate pads over the MKI* folding armour.

As a side note, you can see this Carrier being driven by the adversary, as it is brought along side of a Sherman. See minute 7:49 in: http://www.youtube.com/watch?v=Dpb9_YS3CzE

If you look at the test dimple on the first pic you can make out a small "punch" mark in the middle. That dimple doesnt look like a .303 test hit, too even! On a "hit" you would have some distortion around the outer edge as all rounds dont break up the same on impact. Thats my Tuppence (Nickles...!!!) worth.