Friday, September 15, 2023

Yet Another Gun That Won the War

I could write endlessly about this topic.  Which war?  And from whose point of view?  Both Colt and Winchester claimed they produced the gun that won the West.  Great Britain successfully invaded over half the countries of the world using the Brown Bess musket—the same gun that Mexico used when it lost the Mexican-American War.  And Teddy Roosevelt wrote glowing reports about the Krag-Jørgensen Rifle used in the Spanish-American War.

Even if we narrow it down to a single war (in this case, World War II), there are many claimants.  The British still sing the praises of the Lee-Enfield No. 4 rifle while the Russians are positive that their Mosin-Nagant 1891/30 bolt action rifle was the best weapon in the war.  Naturally, every American knows this is all nonsense, since the M1 Garand rifle was the best rifle of the war by any realistic measure.  (I’ve fired all three and there is no doubt in my mind that the Garand really is the best rifle of the war and the Nagant comes in second.  Rifles are not the only thing the Brits have strange ideas about.)

The U.S. Army Air Corp would argue that “Ma Deuce”, the .50 caliber machine gun, was the definitive weapon of the war, and since it is still being used by almost everyone, everywhere, there is merit to that argument.  The weapon is so reliable, that recently, the U.S. Army removed from its active inventory a machine gun with a three-digit serial number that was over 70 years old.  

Today, however, we are going to look at the Gun That Won the War—at least from the point of view of the US Navy.  According to naval historians, there is absolutely no doubt that the honor goes to the Mark 12 5-inch/38-caliber gun—no surprise if you consider that almost every naval combat ship built between 1934 and 1948 carried these guns.  To that number, you can add Coast Guard vessels, armed merchant vessels, and quite a few of the ships of our allies.  Altogether, almost 8,000 of these large guns were produced.

At the end of World War I, the Navy was reevaluating the need for multiple caliber guns.  Since the navy used 14-inch, 12-inch, 11-inch, 8-inch, and multiple different guns in both 6-inch and 5-inch, the logistics of supplying the ships was difficult.  Some ships, in particular the cruisers and battleships, carried as many as many as four different gun sizes, requiring multiple storage compartments for each.  And since the crews were normally only trained to operate one type of gun, crew training was difficult.

After the war, there was growing recognition that naval ships had to have more effective anti-aircraft guns.  Since the navy was currently using a low-angle 5-inch gun for surface-to-surface combat and a different 5-inch anti-aircraft gun, it was thought that a new 5-inch gun was needed—one that could combine the better qualities of both existing guns.  

Designed the Bureau of Ordnance of the U.S. Navy, the resulting 5-inch/38-caliber gun was a revolutionary design that became the most widely used naval gun of the war.  The Mark 12 was used for ship-to-ship action, it was a deadly anti-aircraft weapon, and it was even used effectively for shore bombardment.  It had a maximum range of almost 16 miles and was effective against aircraft up to 37,000 feet—a height that only the German Arado jet bomber that was introduced late in the war could exceed.  The resulting naval weapon was still being used as late as the Falklands War.

Note.  The caliber of firearms and rifles can be a little confusing, primarily because there was no set authority on determining definitions, and the popular names arose through traditions that varied not by the countries where the guns were developed, but sometimes to the branch of the service that developed them.  In general, for handguns and rifles, caliber is a measurement of the bore size of the weapon.  A .38 caliber revolver fires a pistol round measuring .357 inches wide, .38 inches is the width of the loaded brass case.  On naval cannons, the caliber is a reference to the length of the barrel, as measured by multiples of the muzzle bore.  So the 5” 38 caliber naval gun has a barrel that is 38 times as long as the 5” bore, or 190”. 

The gun, with the highly accurate Mark 37 fire control system to aim it, was a semi-automatic weapon.  When fired, a hydraulic system absorbed part of the recoil, and ejected the spent powder case, cocked the firing mechanism, and opened the breech.  The gun was then loaded by hand, and an electric/hydraulic ram closed the breech.  While the gun was rated to fire 15 times a minute, a well-trained crew of from 15 to 27 men could fire the weapon every three seconds.

The Navy quickly began using the Mark 12 in larger numbers than originally intended, with most large ships replacing all of the intermediary sizes of guns with the new Mark 12, simplifying the logistics of ammunition storage.  The USS Iowa, for example, famously had 9 massive 16-inch guns, but also had 20 Mark 12 5-inch guns.  These were the largest guns carried on aircraft carriers during the war.  The cruiser USS Atlanta, pictured at left, carried sixteen of the Mark 12 guns.

As effective as these weapons were, a major improvement was introduced in 1943.  When the 5-inch guns were used against enemy aircraft, the shells were not intended to actually hit the aircraft, but a timed fuse was set to explode at the altitude of the attacking plane and shrapnel from the exploding round was supposed to destroy the aircraft.  Naturally, with a ship frantically maneuvering during combat, a fast moving airplane, and a rocking ship….well, even with the superb Mark 37 fire control system, on average a thousand rounds were fired for every enemy plane destroyed.  No wonder then that the total number of rounds fired was in the millions!

What was needed was a smart fuse—one that would explode automatically when it got within range of the enemy plane.  Both the British and the Germans were working on a fuse that used a small radar transmitter and receiver that would detonate when the radar unit indicated that the speeding shell was in range.  Making the fuse was relatively easy (they could even be made relatively inexpensively), but making a fuse that could withstand the 20,000 G’s the fuse would experience when the gun fired was seen as impossible.  The best design the British had come up with could withstand 100 G’s, about what a baseball experiences when a major league pitcher burns one over home plate.

The United States has a standard solution for such problems:  Just keeping throwing money and men at the problem until you find a solution.  In this case, it was millions of dollars and 10,000 researchers working at and around John Hopkins.  Most of those involved were not even sure just what they were trying to build.  Take for example the men whose job it was to climb to the third floor of the Pratt Library and toss prototypes out the window to land on the concrete below.  

By 1943, the VT or Variable Timer fuse was ready.  It wasn’t actually a “variable” timer, that was a bit of espionage subterfuge to fool the enemy.  For the same reason, the fuse wasn’t allowed to be fired over land until very late in the war lest the enemy find a defective round and copy the design.  The one exception to this rule was in England where 120 V-1 “buzz bombs” were landing daily.  After the introduction of the VT fuse, 79% of incoming V-1 cruise missiles were destroyed.

In the Pacific Theater, the VT fuses and the Mark 12 gun were immediately effective and were largely responsible for the success at shooting down enemy planes, particularly during the Battle of the Philippine Sea—“The Great Marianas Turkey Shoot.”  Anti-aircraft gunnery at night was improved 370% as soon as the new proximity fuse was delivered.  

As Admiral Forrestal said after the war:

The proximity fuze has helped blaze the trail to Japan. Without the protection this ingenious device has given the surface ships of the Fleet, our westward push could not have been so swift and the cost in men and ships would have been immeasurably greater.

Okay, maybe the 5-inch gun didn’t really win the war, maybe it was just a tremendous help in winning the naval war.  But consider what would have been the result of the war if both Germany and Japan had developed both the 5-inch gun and the proximity fuse early in the war.  It is doubtful that the Allies would have been able to secure air superiority, meaning no strategic bombing, no D-Day invasion, and a more protracted period of war.

I've changed my mind, maybe the Mark 12 5-inch gun did win the war, after all.

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