Is this a shot test

[Dale Jordan]

Is this a test shot mark on the right hand inside lower hull ? I notice this is on other carrier photos I've seen on the forum they look to be all in the same spot . Nothing on the lift side of the hull just wondering .. Dale

[Bob Moseley (RIP)]

Hi Dale - you will see on most Carriers these dimples. This was their method of quality control where .303 shots were fired at the hull to test the bullet proofing of the metal.

Bob

[Dale Jordan]

Thanks Bob . If It failed the test , I wonder if the scraped the complete hull or just replaced the armor in that area .. Dale

[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.

[gordon]

A Brinell Hardness Number ( BHN value ) will give you a decent measure of ballistic penetration resistance up to about 3/8" thick plate, since I'd expect an impression made by a 10mm Tungsten ball.

Over about 3/8" thickness, and depending on the plate production method, the physical characteristics of the metal at the centre of the cross section would be such that a BHN figure would just be a guide, and some chunkier form of testing would be required.

If I was setting it up, I'd have the plate subject to a a drop test, where a known weight was dropped on it from a known height on a particular shape and cross section of pin. It would be reasonably easy to simulate the energy input and physical characteristics of a bullet that way, and the resulting dent would look fairly similar. The result wouldn't be recorded as a pass or fail either, you would record the displacement ( depth ) at the centre of the dent, and make a separate note of any physical damage such as cracking or penetration.

Test frequency would be one or more per type of plate per heat treatment batch and per cast number ( distinguishing between the cast number, which sets the chemical composition, and the heat number, which sets the physical heat treatment characteristics )

If I had to guess, on the 81047 image above, I'd say that someone has done a drop test on the plate, and then a Brinell Hardness at the centre of the drop test mark, probably to generate consistent records as you would know both figures came from the same area of the plate.

If I had to fake up a test report;

Date: 01/01/19xx
Tester: MLU
Cast: ABC123 Bloggs Foundries
Heat: DEF456 Smiths Heat Treatment
Plate Batch: 81047 Production side plate, 5/16" thick
Impression Depth: 3/32" from 50lb load dropped 3 feet on 1/2" standard pin
BHN: 235 using 10mm Tungsten indenter at impact centre.
Notes: No evidence of cracking or penetration

[motto]

Around forty years ago I was involved in a discussion about what would and what would not penetrate a carrier hull in the way of small arms fire. This came about because there was an abandoned, stripped out, hacked around carrier hull laying around on a property where my workmates used to hold occasional social functions (read 'booze-ups').

It was decided that the only way to settle the argument was to carry out some practical testing. Subsequently a return was made to the site in the cold light of day and all of us completely sober with a selection of firearms and ammunition. Firing was at right angles (square on) and carried out at a range of 30 to 40 feet with the impact area being on standard thickness hull armour ie not frontal. To the best of my memory the findings were as follows:-

.303 Mk 7 Ball - A bit of a dent, bullet vaporised.
.577/450 Martini Henry - A shallower dent, bullet vaporised.
.303 AP (don't recall Mk No) - Consistent penetration of tungsten carbide core.
30-06 AP - Inconsistent penetration of hardened silver steel core. Core break-up.

Nothing we had would penetrate the frontal armour.

The dimple in Michaels picture is nothing like a bullet strike, either AP or Ball. The edges are too defined.

David

[Lynn Eades]

Thank youMichael, Hanno and Gordon, for you detailed posts.
Here is the rear flap from a 1938 Bren NoII, MkI, (HMH243) The two indentations would fit remarkably well the descriptions given in the last two posts, re the Brinell test.

[Richard Farrant]

The Daimler armoured vehicles made during WW2 had a much more accurate hardness test and done with a very small ball probably only a few millimetres in diameter. Every armour plate had a small area surface ground, approx. 15mm square and the ball mark within it. This way the indentation could be accurately measured for depth. Not sure if this was Rockwell or Brinell method now, without checking.

[Michael R.]

Did I cause a misunderstanding in my previous post? Regarding the image of the numbered armour plate with dimple and straightening hammer tool mark impressions: I am quite confident this dimple tool mark impression was made following the heat treating process, and that it was done by a method similar to the Brinell or Rockwell testing protocol. This same plate has these test marks at regularly spaced intervals. It has nothing to do with a rifle cartridge bullet being fired from a barreled weapon or other device for testing purposes.


As Hanno indicated:
"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" (paraphrased)

Reference: CALCE and the University of Maryland, sourced 25 May 2013 from WWW at URL: http://www.calce.umd.edu/TSFA/Hardness_ad_.htm, quoting from http://www.wargamer.org/GvA/background/hardness1.html (does not load)


Posted in response to:
"If you look at the test dimple on the first pic you can make out a small "punch" mark in the middle. That dimple doesn't look like a .303 test hit, too even! On a "hit" you would have some distortion around the outer edge as all rounds don't break up the same on impact."
and:
"The dimple in Michael's picture is nothing like a bullet strike, either AP or Ball. The edges are too defined."

[Mike Cecil]

I believe the testing was done on the plate at the manufacturer, not once the plate was cut up into hull sections, or after it was assembled. The test was specific to ABP3 (Australian Bullet Proof No.3) plate, as this type of plate manufacture/formula was unique to Australia. As far as I can tell from the limited info I've located so far, the testing was done with a test rig and was supposed to simulate a bullet strike by service Ball ammunition, but did not actually use a ball projectile. I've been unable to find any diagrams or descriptions of the test rig, but it was built so the testing was repeatable and consistent, ie was a valid comparative measure of the brittleness and armour qualities of each ABP3 plate. You will find that all the marks - which I agree do not look anywhere like a Ball round impact at 2500-odd fps - are the same and show a flat 'punch' mark, rather than exertion of steady pressure or the impact of a pointed bullet.

ABP3 had a tendency to become very brittle if the final quenching process was done at a slightly varied temperature - early Cruiser tank hulls consistently failed the test because of the difficulties of maintaining the correct temp across such a large structure, whereas flat plate was comparatively easier to control.

ABP3 is unique to Aust armoured vehicles, so I doubt that the exact same rig with a captive pin was used in the UK or elsewhere. Certainly, it appears to be a variation on the standard test method, with pressure, speed of application etc tailored to test the qualities of ABP3, particularly brittleness.

Mike C

[David Dunlop]

Michael.

That test mark you showed was on six locations on one side of my Mk II Cdn Carrier - two, top and bottom rear, centre and front (upper front missing when this piece of plate was cut out. The other side of the carrier had the test marks in the same locations, but each location was a grouping of three marks in the pattern your middle three finger tips would make. The marks were more 'random' on the rest of the carrier - single marks or none at all.

Mike.

You are correct in that these tests were done by the plate manufacturer, prior to delivery to the vehicle maker (at least that is how it worked here in Canada with the plate made for the Carriers built by Ford). The armour plate was time-consuming to make and expensive for the day. It had to be right before going into production. A neighbour of my parents many years ago had been an engineer at the Ford Windsor plant during the war and he told me that when the pattern torch had cut back the side armour at the upper front ends, these small pieces were then used in the fabrication of the armour shrouds surrounding the fan/rad assembly, immediately aft of the front bulkhead. Waste not, want not.

David

[gordon]

Originally Posted by Richard Farrant

The Daimler armoured vehicles made during WW2 had a much more accurate hardness test and done with a very small ball probably only a few millimetres in diameter.

Just another explanatory note here, although the ball used to make the impression was 10mm diameter, the resulting impression could be just 2, 3, or 4 mm on most surfaces, so that would fit quite well.

The surface grinding Richard mentions was to clean up any surface roughness and remove any effects of surface hardening, as the hardness value can drop quite dramatically if you remove as little as 1/32" of metal from the surface.

[David Dunlop]

Rummaged in an album this morning and found a photo of the three cluster hardness test on my old carrier, along with a couple of photos of it 'as found' in a farm yard. The chap had five young grand kids and played in it a lot, but the instruments and mirror were complete and untouched. Used to end great stuff 20 years ago! Harder to do now!

David

[Bob Moseley (RIP)]

Hi all - I have lived with this story for many years. I cannot exactly remember where I heard it but I am sure one source was a WW2 Carrier test driver. However the gauntlet has now been thrown down and the truth needs to be revealed. Watch this space.

Bob

[eddy8men]

i remember during my REME trade training a machine called an izod impact tester. it was basically a weighted pendulum with a ball bearing on the end that hit the test piece with a known amount of force this enabled the material to be rated for hardness by measuring the depth of the indentation. i'm sure carrier armour would have been tested with a machine like that but i'm also sure that most dents you see on a carrier are caused by bullet strikes. my carrier has plenty of dents of varying sizes and 3x 11.5mm holes in the left side panel caused by what i assume to be armour piercing rounds from a boys rifle. if the dents were caused by a measuring machine then the dents would be uniform and all the same depth but if a dent is ragged or oblong it make sense that it was caused by a bullet.
the first pic shows 2 bullet holes on the left panel and the second pic shows the strike marks on the opposite side, the third pic shows a quite large dent but with a flat bottom ? and the last pic shows another penetration hole near the top of the armour that has bent the side with the force of it.

rick

[Ian Patrick]

The front armour plate on my LP2A carrier and some other LP2/2A carriers I've seen have test marks that appear to have been caused by a bullet-like impact.

These appear to be reasonably consistently located in the same spot(s) on various different carriers which would seem to indicate that the test was undertaken either after the carrier was assembled or at least when the front armour plate had been cut to shape. Logically this would indicate the testing was done at the carrier assembly plant rather than the steel manufacturing plant.

These marks have not been caused by a ball striking the plate but appear to be from a small diameter sharp object hitting the plate with some force.

Any ideas?

Ian

[Ian Patrick]

Another test mark from a different carrier, SA Railways LP2A 2515.

[45jim]

Gentlemen,

No armour plate destined to be assembled onto or into a vehicle is proofed by actual ballistic testing. Any marks you see on your carriers either are a result of mechanical testing of the hardness using conventional test methods at the steel works or a result of "life experience" during the past 70 years.

Armour plate is produced just like any other blend of steel. It is composed of a carefully balanced mix of iron, carbon and other additives smelted into ingots. Later, those ingots are either cold or hot rolled into plate which is further heat treated to achieve the hardness and mechanical properties set down in the relevant specification. The standards, methodology and instruments used to confirm the hardness of armour plate are the same used for any production run of steel.

Armour plate production today is not much different. Plates are manufactured and heat treated in "heats" and a sample of the "heat" is tested to ensure the hardness meets the standard and metallurgy is scientifically examined, also a sample is sent to a ballistic test range to verify its performance. As the volume of successful testing increases the amount of testing will be reduced. Early in production every lot may be tested but later it may be every two or every three, depends on the demand of the customer.

Ballistic testing is "destructive testing" while hardness testing (in steel anyway) is considered "non-destructive testing" so there is no way that shot plates are going to end up on a carrier. As you can imagine with any scientifically designed standard, hardness is calculated as "averages" so many impacts may be taken on a single surface to get an accurate reading. Ballistic testing is the same, we often fire 10 rounds (or more) at a target at various velocities to ensure we have an accurate value of the Ballistic Limit (BL).

If you are curious, you can look up MIL-A-46100, this is the NATO specification for 500BHN armour plate steel. It details everything including the type of testing required and the ballistic limits samples must achieve. You will notice that the plate is tested for Brinell hardness, Impact testing (Charpy V-notch), bending test and finally ballistic sample testing. This is not a classified standard.

There are certainly other blends such as RHA (rolled Homogeneous armour) which is somewhat softer and more ductile than 46100, but this standard originated in WWII and closely reflects what was used on the carrier.

[carrierbarry]

Rick

Those dent marks are just from your driving.
I've seen you in Tesco car park.

Ha ha !!!

[eddy8men]

hey barry if you think the carrier is bad you should see my works van

rick

[David Herbert]

Rick,

Your van doesn't count, it has been used by builders, who are widely known for their destructive properties. If it had been shot at it would be only partly destroyed. The Cromwell looks good though!

David

[Paul Dutton]

I thougt that living m manchester all vans wold have been `shot tested` at sometime in their lives!!!!