[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.