OT What-If History Discussion: USS Iowa vs. IJN Yamato

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Iowa had radar controlled fire control system, Yamato did not.

Game over.

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This isn't a real debate is it? Murica' frick yeah

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This isn't a real debate is it? Murica' frick yeah

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IIRC, we found some steel like the Yamato's at the end of the war and were only able to penetrate it after it was shot point blank.

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TWO BALLISTIC TESTS:

PROJECTILE USED:

U.S. Navy 2700-lb 16" Mark 8 Mod 6 AP with inert filler ("BL&P") (last version of this projectile manufactured during WWII)

OBLIQUITY: Near-normal (0°)

TEST #1 on 16 October 1946 (IMPACT #33443):

POINT OF IMPACT: Upper center near joint with turret roof at 0.33° obliquity from normal where plate was 25.99" thick.

STRIKING VELOCITY: 1992 feet/second (607.2 m/sec)

RESULT: Complete penetration and plate snapped in two through impact between side edge and upper end of curved gun port hollow. Hole more-or-less cylindrical, with little difference between front and back of plate. Numerous small cracks also put in plate around impact. No damage to projectile indicated, though projectile had considerable remaining velocity and ended up in the Potomac River, never being recovered. Considerable amount of lamination noted in hole (layering effect parallel to face, much like pages in a book glued together). The upper portion of this broken plate is now on display at the U.S. Navy Memorial Museum at the Washington Navy Yard, Washington, DC, just in front of the old Gun Factory building which houses much of the museum today.

TEST #2 on 23 October 1946 (IMPACT #33459):

POINT OF IMPACT: About halfway between first impact and base of plate, centered between cutout for gun port and left edge of plate, at 0.5° obliquity from normal where plate was 25.98" thick.

STRIKING VELOCITY: 1707 feet/second (502.3 m/sec)

RESULT: Projectile nose tip only penetrated 21" (53.34cm) into the plate, though punching a hole entirely through. Projectile was completely undamaged (merely lost its windscreen and AP cap, as usual). Plate had exactly the same thing happen to it as with the first test, with numerous small cracks, many laminations, and a complete break through hole between left edge and curved gun port cutout.

CONCLUSIONS:

The U.S. Navy Ballistic Limit (complete penetration minimum velocity with this projectile at normal) estimated at 1839 feet/second (560.5 m/sec), plus or minus 3%, which gives it about a relative plate quality of 0.839 compared to U.S. Class "A" armor (estimated, as no such super-thick plate was ever made in the U.S.). This was about the same as the best WWI-era British KC-type armor, which was what the Japanese were trying for--they had not attempted to make improved face-hardened armor, as the U.S. Navy did during the 1930's, for actual ship installation.

The plate was excessively brittle internally, with too much "upper bainite" crystal structure due to too-slow cooling. This was due to using the same pre-WWI British Vickers KC-type armor-hardening techniques on plates over 17" (55.8cm) thick, for which they were never intended. This problem was solved during WWII, but no more VH was ever made except for some thin experimental plates. Brittleness did not seem to reduce resistance to penetration, though cracking might cause problems due to hits that ricocheted off.

Note that one of these experimental plates--7.21" (18.3cm) VH plate NPG #3133--was patterned on Krupp KC n/A (probably from data traded with Germany during WWII) and was tested by the U.S. Navy at the NPG using 335-pound 8" Mark 21 Mod 3 and Mod 5 (the latter with the super-hard AP cap, which turned out to be required to penetrate that plate intact) during this same test series. It was found to be THE BEST PLATE OF ITS THICKNESS RANGE (6-8" (15.2-20.3cm)) EVER TESTED BY THE U.S. NAVY, even though its steel was of the same rather poor quality as the other VH plates tested!!! This caused the U.S. test conductors to state that obviously they did not understand what it took to make a high-quality Class "A" plate, since the 7.21" VH plate should not have been so good from everything they thought they knew about face-hardened armor!!! Obviously the Japanese could make armor as good as anyone if the specifications had required it!

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At about 40,000 yards, the U.S. Navy 16"/50 firing a 16" Mark 8 Mod 6 AP projectile (the later Mod 7 and Mod 8 designs were post-WWII, so I usually do not count them and they were no better ballistically, to my knowledge) will hit at about 45° downward angle and 1607 feet/second (489.8 m/sec). Just as with a point blank hit at 2500 feet/second (762 m/sec) and 45° obliquity, this hit too will barely hole the plate as the projectile is hitting at 0° (normal) obliquity, though not completely penetrate it. Any slight barrel wear will lower the muzzle and striking velocities and no holing will occur at THESE OR ANY OTHER ranges, as mentioned. However, this is so far above any real fighting range (even with radar it is hard to see the target due to the earth's curvature interfering, especially in any kind of imperfect seeing conditions) that I do not even consider it in my computations, while putting the gun barrel up to almost touching the enemy turret is also a pipe dream in real life! Thus, no holing or complete penetrations, ever, though possibly some cracking of the plate and possible jamming of the turret if the crack-off plate piece is dislodged badly enough.

Therefore, these plates are the only warship armor plates that could not be completely penetrated by ANY gun ever put on a warship when installed leaning back at 45°, as they were in the actual turrets!!! Even to completely hole the plate all the way through at that inclination requires a brand new 16"/50 Mark 7 or German 38cm SK C/34 gun at point-blank range firing the latest versions of their respective AP projectiles; it might be cracked at a lower striking velocity, but no hole put entirely through it! AND THEY SAID GUNS HAD COMPLETELY OVERMATCHED ALL ARMOR--*NOT SO*!!!

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Another major debate has always been what would have happened if the Bismarck had faced the HMS King George V one on one without being damaged and still operating at 100%.

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