In all projectile tests against armor, projectile must completely penetrate the armor plate specified at the obliquity and striking velocity specified with no damage that would reduce the explosive effectiveness of the projectile after penetration (no cracking into or breakage open of the explosive cavity, the base plug still seated tightly, and the fuze still functional - this last was determined in these fuze-less tests by examining the distortion/cracking/breakage of the lower projectile body and base plug after the test).

The tables below give the range of acceptable possible test conditions: Striking Velocities (Vs) in feet/second for given plate thicknesses and impact obliquities (Ob), where right-angles is Ob=0 degrees. Which one to use was determined by the U.S. Naval Proving Ground ballistic test controller at the time of the test.

Only 1 failure allowed in the 3 projectiles fired (retest possible if allowed by test controller).

Some Mark 29 & 30 projectiles had no filler or fuze. US Army M66 0.016-delay fuze was used when filler added.

In 10,000 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile for fragmentation test from 1^st lot only (unless further tests needed for some reason); 12 projectiles for flight test from 1^st lot of new contract (range table verification) and 6 for flight test from each 5^th lot thereafter (quality control).

Maximum Striking Velocity (Vs) in any test was 2,550 ft/sec.

In 500 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile for fragmentation test from 1^st lot only (unless further tests needed for some reason); 12 projectiles for flight test from 1^st lot of new contract (range table verification) and 6 for flight test from each 5^th lot thereafter (quality control).

Maximum striking velocity in any test was 2,200 ft/sec.

Mark 19 was primarily for guns in older heavy cruisers prior to the BALTIMORE Class (could be used in all U.S. Navy 8" guns, if needed, though). Similar Mark 20 was for U.S. Army 8" Coast Artillery guns (8" Field Artillery did not use AP projectiles), but Navy guns could fire them.

In 500 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile for fragmentation test from 1^st lot only (unless further tests needed for some reason); 6 projectiles for flight test from 1^st lot of new contract (range table verification) and 3 for flight test from each 5^th lot thereafter (quality control).

Maximum striking velocity in any test was 2,500 ft/sec.

These were for the new BALTIMORE and DES MOINES Class heavy cruiser guns only. They were too long and heavy for the older cruisers’ magazines.

In 500 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile for fragmentation test from 1^st lot only (unless further tests needed for some reason); 6 projectiles for flight test from 1^st lot of new contract (range table verification) and 3 for flight test from each 5^th lot thereafter (quality control).

Maximum striking velocity in any test was 2300 ft/sec.

These were for new ALASKA Class cruiser guns only. The remaining 12"-gunned battleships still used their old 12" Mk 15 MOD 6 "Midvale Unbreakable" (1916-vintage) shells, usually with new Mk 21 Base Detonating Fuzes.

In 500 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile for fragmentation test from 1^st lot only (unless further tests needed for some reason); 6 projectiles for flight test from 1^st lot of new contract (range table verification) and 3 for flight test from each 5^th lot thereafter (quality control).

Maximum Striking Velocity in any test was 2,300 ft/sec.

Mark 20 had a short windscreen for TEXAS Class magazines.

In 500 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile or fragmentation test from 1^st lot only (unless further tests needed for some reason); 6 projectiles for flight test from 1^st lot of new contract (range table verification) and 3 for flight test from each 5^th lot thereafter (quality control).

Maximum Striking Velocity in any test was 2,500 ft/sec.

Mark 5 were for COLORADO Class guns. Mark 12 were almost identical projectiles for US Army Coast Defense guns (different fuzes and no-dye-bag windscreens). Later, some Mark 12 projectiles were changed back to Navy-standard Mark 5 Mod 6 projectiles with Navy Mk 21 Base Detonating Fuzes.

In 500 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile for fragmentation test from 1^st lot only (unless further tests needed for some reason); 6 projectiles for flight test from 1^st lot of new contract (range table verification) and 3 for flight test from each 5^th lot thereafter (quality control).

Maximum striking velocity in any test was 2,400 ft/sec.

These were for the new 16"/45 & 16"/50 "light-weight" guns only. At 4.5-calibers in length, they were too long for the COLORADO Class magazines.

In 500 projectile lots (except for initial lots, as specified by BuOrd).

3 projectiles for ballistic test from each lot; 1 projectile for fragmentation test from 1^st lot only (unless further tests needed for some reason); 6 projectiles for flight test from 1^st lot of new contract (range table verification) and 3 for flight test from each 5^th lot thereafter (quality control).

Maximum striking velocity in any test was 2,400 ft/sec.

• ^1.11.2The Class "A" armor used here was not regular U.S. Navy WWII ‘Thick Chill’ Class "A" armor, which was not made in thicknesses under 4" (thinnest part of a 4-6" tapered cruiser belt armor plate) or 5" (uniform-thickness cruiser armor plate). The armor in these tests was US Army light-tank-and-armored-car-type face-hardened chromium-nickel armor which was made using a form of the Harvey process with a cemented (high-carbon- content layer) extremely hard face about 1-1.5" thick and a ductile homogeneous-armor-type normal-carbon-content back layer with a step-function hardness drop at the back of the hard face (no gradual softening in a thick face layer behind the cemented surface layer, as with usual Navy Class "A" armor).
• ^2.12.22.3These Class "A" tests above were shifted up by Revision "J" due to a 1.025% average resistance increase in the quality of Class "A" armor.

This article is copyrighted 2011 by Nathan Okun and is reproduced on NavWeaps.com with permission.

24 July 2011

Benchmark.