Tag Archives: 1.1″ Quadruple

Warship Wednesday, Feb. 23, 2022: The Troublesome Chicago Piano

Here at LSOZI, we take off every Wednesday for a look at the old steam/diesel navies of the 1833-1954 period and will profile a different ship each week. These ships have a life, a tale all their own, which sometimes takes them to the strangest places. – Christopher Eger

Warship Wednesday, Feb. 23, 2022: The Troublesome Chicago Piano

Official U.S. Navy photograph, now in the collections of the National Archives. 80-G-21955

Here we see the crew on a four-barreled 1.1-inch/75cal anti-aircraft gun located on the flight deck of the famed Yorktown-class aircraft carrier USS Enterprise (CV 6), ready for the moment when the word “Commence Firing” is passed. The photograph was released 3 April 1942, just a few months after the much-disliked “Chicago Piano” had its baptism of fire.

The Navy in the 1910s, rushing into the Great War, one in which floatplanes and Zeppelins were a real (even if not perceived great) threat to warships at sea and nearshore, began adding a handful of “balloon guns” and anti-aeroplane pieces to their vessels which extra deck space. This boiled down to stubby 3″/23 mounts placed on higher-angle AA mountings as well as, after 1916, Maxim/Hotchkiss Mark 10 37mm “1-pounder” Pom-Pom automatics of the type which was already in use in the Royal Navy at the time.

The Mark 10 1-pounder Pom Pom (Model E Hotchkiss), seen at Watertown Arsenal in 1916 with its deck penetrating naval mount. Note its water jacket and ability to go almost max vertical. The gun itself, in earlier formats with a more limited mounting, had been used by the Navy as far back as the Spanish-American War.

The Hotchkiss pom pom, seen in a period postcard, left, and fitted on the flush deck destroyer USS Israel in 1918, NH 102923. While these guns served in the U.S. Navy only briefly and were withdrawn soon after the war, other European powers continued to use them well into WWII.

Although the 37mm pom pom gun could be manned by a single bluejacket in a pinch, and it was capable of firing 25 shells in a minute before it needed reloading, its short-cased ammunition was limited to a range of just 3,500 yards.

Something better…

By the late 1920s, directly after Billy Mitchell’s antics, while the Navy shrugged off the possibility that land-based bombers could destroy capital ships underway, they quietly began upping their AAA capabilities with a trio of weapons.

This trifecta included the M1921 and later M2 water-cooled .50-caliber Browning heavy machine gun on pedestal mounts with “tombstone” magazine boxes. Capable of running through a 110-round belt in about a minute, it had a higher rate of fire but an even smaller round than the old 1-pounder pom pom with an engagement range of under 2,000 yards.

It was the water-cooled .50 cal that Dorie Miller became famous on at Pearl Harbor.

USS Enterprise (CV-6), view of part of the .50 caliber anti-aircraft guns gallery in action against attacking Japanese planes during the raid on the Japanese-held Marshall Islands, 1 February 1942. The wing in the background is from one of the Douglass SBD-3 Dauntless aircraft in the carrier’s air group. NH 50935

While the .50-cal was the low end of the USN’s interbellum AAA, the high end was the newly developed 5″/38 DP Mark 12 gun on Mark 21 mounts, which began reaching the fleet’s destroyers in 1934 with USS Farragut (DD-348), could fire AAC shells out to 17,270 yards with a ceiling of 37,200 feet. Early Mk 33 directors could concentrate this fire with great accuracy– for the early 1930s– and better, faster versions of the 5″/38, augmented by late 1942 with radio proximity fuses (VT fuses) would make the guns much more effective against aircraft.

This left the mid-range between the big 5-inchers and the puny .50 cals. This is the space the 1.1-inch gun filled.


As detailed in “The Chicago Piano” by Konrad F. Schreier, Jr. in Naval History, July/August 1994, the gun took six years to hammer out from the prototype to a (semi) working example:

The 1.1 gun was designed as a weapon to be used against dive and horizontal bombers and as such supplement the defensive characteristics of the caliber .50 machine gun. The first definite action in this direction took place on October 11, 1928, when the Chief of the Bureau announced a meeting of a Special Board on Naval Ordnance for October 17 to consider and submit a plan for the development and test of a machine gun of 1″ or greater. As a result of this and successive meetings, the decision was made to develop a 1.1″ machine gun.

On December 13, 1928, Mr. C.F. Jeansen, a Bureau Engineer, began an investigation of the weight of ammunition for the gun and in March 1929 Mr. Burk and Mr. Chadwick, likewise Bureau Engineers, were designated to design the gun mechanism. The round as finally adopted weighed 2 pounds and employed a .92 pound percussion-fuzed projectile. The design of the gun mechanism was completed in 1930 and tests on the initial models were carried out in March, April and May 1931. The tests, which demonstrated a cyclic rate of 90 r.p.m., were characterized by primer blow backs, misfires, and stuck cases—as well as magazine and cradle difficulties. During the next two years, designers corrected these faults and the cyclic rate increased to 140. The design was turned over to the Naval Gun Factory for production in 1934.

The shell used, spec’d out as 28x199mmSR, was a handful, no doubt.

1.1 shell OP4 plate 16

For reference, the closest thing in the Navy’s arsenal today is the 25x137mm Bushmaster as used by the Mk38 chain gun system or its follow-on 30×173 mm Bushmaster II as used in the Mk 46 gun system.

From my own collection: a .30-06 M2 ball round as used in the M1917/M1903/M1, the .50 cal BMG as used in the M2 machine gun, and a 25x137mm Bushmaster dummy. Keep in mind that the 28×199 as used by the 1.1-inch gun is about 2.45-inches longer. (Photo: Chris Eger)

Ordnance Pamphlet No. 4 (May 1943) mentions the following about the fuzing of the 1.1-inch shell, “For AA projectiles in the 1.1-inch caliber, supersensitive nose fuzes are provided to ensure bursting action immediately in the rear of very light plate or fabric, while, for common and high capacity projectiles of 3-inch and up, time fuzes are furnished to burst the projectile at the point desired in the air.”

As noted by Tony DiGiulian at NavWeaps, “A 1934 report to the Navy General Board concluded that a single 1.1″ (28 mm) hit on any part of an aircraft would probably result in a forced landing.”

The following range table from Ordnance Pamphlet 1188 (June 1944), giving a range of 7,000 yards, although its best hope of hitting something was closer to 2,000 yards. The ceiling for the gun was 19,000 feet.

When it came to utilizing the weapon in the fleet, which took until 1938 before it reached what could be termed IOC today, the “one-point-one” was used in a four-gun side-by-side water-cooled mounting that weighed 5-tons, later ballooning to almost 9-tons in its final Mark 2 Mod 6 mount.

Quad 1.1″ (28 mm) mounting. Sketch from OP-1112. Image courtesy of HNSA, via Navweaps.

Clip-fed via four hoppers, one for each gun, the mount had a theoretical rate of fire of about 550 rounds per minute. Between all the loaders, the gun mount captain, slewers, and elevators, it required upwards of 15 men to make one of these work, and that isn’t counting clippers in clipping rooms and humpers in the magazines sending up rounds from down in the bilges.

Each 8-round clip weighed 34 pounds when loaded and empty clips can be seen being manually removed by gun crew members in this great action shot.

1.1 Chicago Piano AA gun USS Philadelphia CL-41 Operation Torch, LIFE Eliot Elisofon

USS PENNSYLVANIA (BB-38) 1.1 Chicago Piano clip hoist inside the kingpost 19-N-28408

USS PENNSYLVANIA (BB-38) kingpost. Note the two 1.1 Chicago Pianos under the tripod pagoda. 19-N-28416

USS PENNSYLVANIA (BB-38) eight-round 1.1 ready service clips, essentially the M1 Garand’s en-bloc clip on steroids

The guns were soon fitted to a range of new-construction destroyers, cruisers, and aircraft carriers in the late 1930s and early 1940s, and fitted to older battleships and carriers. 

1.1″ Quadruple Anti-Aircraft Machine Gun Mounting on the new carrier USS Wasp (CV-7), 26 February 1941. 80-G-464857


On the morning of 7 December 1941, the Piano had its first recital and was credited, at least in initial reports, with its first kill, that from the new Porter-class destroyer USS Selfridge (DD-357). Commissioned on 25 November 1936, she had four twin 5″38s, two quad 1.1s, and some .50 cals. Only the latter two got into play against the Japanese that day.

From Selfridge’s report:

This vessel participated in the defense of Pearl Harbor and the ships based therein during the air raid of 7 December 1941.

Berth occupied was X-0 on heading approximately north-east, outboard and starboard side to U.S.S. Case, Reid, Tucker, Cummings and Whitney.

Service .50 caliber and 1.1″ caliber ammunition was clipped and in ready boxes at all machine guns prior to the action. Guns were ready for instant use except for being manned and loaded.

Nine officers and ninety-nine percent of the crew were on board.

Approximately four minutes before morning colors the Officer of the Deck witnessed the launching of a torpedo against the U.S.S. Raleigh by a Japanese plane. Almost simultaneously came a report from the signal bridge that the Naval Air Station was on fire.

The Officer of the Deck sounded the alarm for general quarters, set condition affirm and directed the engineering department to light off boilers and make preparations to get underway.

At about 0758 Selfridge .50 caliber machine guns were firing on Japanese planes, shortly followed by the 1.1″ machine guns. It is believed that these guns were the first to fire in this area.

Two enemy planes fired upon were seen to crash. One was hit by the after 1.1″ while diving on the Curtiss. The wing was sheared off causing the plane to crash near the beach at Beckoning Point. Another plane flying low on a southerly course to westward of the Selfridge released a bomb in the North Channel opposite the U.S.S. Raleigh and crashed in flames in the vicinity of the U.S.S. Curtiss while being fired on by the forward 1.1″ machine gun. A third plane, under fire by the forward 1.1″, was seen to disappear behind a hedge halfway up a hill at a location bearing about 045 True from the Selfridge. A fourth plane, hit in the underpart of the fuselage by the port .50 caliber machine gun, started smoking and when last seen was headed toward a cane field to the northward of the Selfridge. It is now known definitely however that this plane crashed.

850 rounds of 1.1″ and 2,340 rounds of .50 caliber were expended during the action. There were no personnel casualties. The only evidence of material casualty is a small conical shaped dent in the starboard side of the director which appears to have been made by a small caliber machine gun bullet.

The performance of the ship’s equipment was excellent, as was that of the crew. At no time during the raid was there a lull in firing caused by an interruption of ammunition supply. Men not engaged at the guns broke out and clipped ammunition in a most efficient and expeditious manner. The conduct of no one officer or man can be considered outstanding because the conduct, cooperation, coolness, and morale of the crew as a fighting unit was superb.

According to an October 1945 report, an estimated 43 planes (actually just 29 by all sources) were shot down on that Day of Infamy, an amazing 27 of them with .50-caliber machine guns, 8 with 5-inch, six with 3″/50, and just two with 1.1s– the latter by Selfridge.

However, the rest of the war proved the 1.1 was lacking and, unliked by almost everyone involved with it and prone to jams, its days were numbered.

Still, it went forward with the fleet throughout 1942, seeing action in all theatres. In all, the Navy assessed the 1.1 fired 57,131 rounds that year, accounting for 38 enemy aircraft, a rate of 1,503 rounds per kill.

Mail transfer at sea, circa 1942. The mailbag is high-lined between the photographer’s ship and a Benson (DD-421) class destroyer, whose after deckhouse is seen. Note Two-tone paint; 1.1″ quad anti-aircraft gun; life rafts; stub mainmast, ensign, and comm. pennant; searchlight; depth charge throwers. 80-G-K-15338.

North African Invasion, 1942. Crewmembers of one of the Northampton-class heavy cruiser USS Augusta (CA-31)’s 1.1″ anti-aircraft guns eat sandwiches at their battle station, during operations off North Africa in November 1942. Note breech of their gun at left, with ready-service ammunition stowed along with the splinter shield. 80-G-30439.

North African Invasion, 1942. A 1.1″ anti-aircraft gun on alert aboard the carrier USS Ranger (CV-4) during the Torch landings, November 1942. Note the loading hoppers and crew waiting with fresh clips. 80-G-30334.

The Lassen-class ammunition ship USS Rainer (AE-5), view of the ship’s bridge, taken at the Mare Island Navy Yard, 15 April 1942. Note 1.1″ anti-aircraft guns on each bridge wing. 19-N-29183.

Omaha-class light cruiser USS Milwaukee (CL-5) at New York Navy Yard, 7 January 1942. Note the 1.1″ anti-aircraft gun and its Mk44 director. 19-N-27090.

1.1 Chicago Piano AA gun, USS Philadelphia CL-41, Operation Torch, LIFE Eliot Elisofon

Seydisfjord Seyðisfjörður fjord Iceland June 1942, PQ-17 convoy, USS Wichita CA-45 with 5in/51 and 1.1-inch Chicago piano next to USS Wainwright DD-419. HMS Somali (F33) is in the background. LIFE Scherschel 

Another image of the above, showing the 1.1 to the top left

One was also used ashore in the Philippines that year, manned by the Army against the Japanese invasion.

Via the Moore Report: 

Also, late in January 1941 a 1.1-in quadruple mounted automatic weapon intended for shipboard service, together with several thousand rounds of ammunition, was turned over to the Defense by the local Naval authorities. Under supervision of the Machine Gun Defense Commander that weapon was emplaced on an especially constructed concrete base atop Malinta Hill. A small Crossley automobile motor, a tank and a small boat pump, all salvaged, were used in the water cooling system.

Manned by a detachment of men selected from the 3d Battalion, 60th Coast Artillery (AA) and trained by a Naval gunner, it was assigned to Mobile for tactical control and first got into action on or about 11 February. Although its effectiveness was reduced because there was no director available, the “one-point-one” rendered good service-mainly through its apparent effect on enemy morale, and particularly in the zone lying between the minimum and maximum effective ranges respectively of 3-in guns and .50-caliber machine guns-until it was destroyed by enemy artillery fire a few days prior to the capitulation.

Fading away, 1943-45

The Piano soon gave way to the much more effective 20mm/80 Oerlikon, 40mm/60 Bofors, and various marks of updated DP 5-inch high-angle guns, the new trifecta.

Kodachrome showing 5″/38 guns firing in gunnery practice, on board an Essex class aircraft carrier in the Pacific, circa 1944-1945. Note 40mm gun barrels in the foreground, also firing, and manned 20mm flight deck gallery beyond. 80-G-K-15382

Nonetheless, the 1.1 was still seeing combat into 1943 and later as many of the old mounts were still afloat and on ships forward-deployed in combat zones.

A 1.1-inch quad anti-aircraft machinegun mounting located on the starboard side amidships of the Brooklyn-class light cruiser USS Nashville (CL-43). Photographed 11-13 May 1943, before or just after the 13 May bombardment of Japanese positions on Kolombangara and New Georgia islands. Note the metal shroud installed around the barrels of this gun mount. NH 97963 cropped

80-G-54554: Battle of the Kula Gulf, July 5-6, 1943. Aboard USS Honolulu (CL 48). Shown is the night gunnery by the 1.1 gun crew on superstructure lit by gunfire.

Check out this rare color footage, from the light cruisers USS Helena (CL-50) and the USS St. Louis (CL-49) in June 1943, showing a 1.1 gun crew in action against Japanese aircraft.

For 1943, the Navy assessed 10,727 1.1-inch shells that had been fired in anger, accounting for four enemy aircraft. Although a further 18,138 shells were fired in 1944 and 45, the system would claim just two additional kills in the last 20 months of the war. In all, the 1.1 fired 85,996 rounds during the conflict for 44.5 kills, just two percent of all enemy aircraft downed, at a rate of 1,932 rounds per hashmark.

By comparison, during World War II, the Navy experience was that it required an average of 11,143 rounds for a .50 caliber machine gun to bring down an aircraft. The .50 caliber weapons on ships were credited with 65.5 aircraft kills for 729,836 rounds expended. This, at least, shows that round-per-round, at least the 1.1 was more effective than the .50 cal.

It was also more effective than the 20mm Oerlikon, which although it downed 617.5 aircraft (28 percent of those on the balance sheet) during WWII, it needed a mean of 5,287 rounds for each of those kills. Ironic.

Only the larger caliber 40mm, 3-inch, and 5-inch mounts were able to best the rounds-to-kill ratio of the 1.1.



At least one was recycled for use by the Japanese during WWII, perhaps the one mentioned in the Moore report.

Dismounted and wrecked U.S. Navy 1.1″ anti-aircraft gun mount, photographed on Corregidor after its capture by the Japanese in May 1942. Copied from the Japanese book: “Philippine Expeditionary Force,” published in 1943. Courtesy of Dr. Diosdado M. Yap, Editor-Publisher, Bataan Magazine, Washington, D.C., 1971. NH 73589

Others still stand guard on the doomed American wrecks on the bottom of the Pacific, especially those from 1942.

These are the two quad guns just aft of the exhaust. USS Lexington, via RV Petrel

USS Astoria CA-34’s 1.1-inch guns. , RV Petrel

USS Hornet CV-8’s 1.1 inch 75 cal Mark 1 anti-aircraft guns. Note how good the waterlines look, even after 80 years underwater. RV Petrel

USS Wasp (CV-7)’s quad 1.1 Chicago Piano. RV Petrel

Few remain in museums, with the 1.1 retained in a few battleship parks, the last fans of the sad Chicago Piano.

1.1 Chicago Piano AA gun on museum ship USS North Carolina

Lastly, the guns showed up in CGI format in the recent film, Midway


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