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Title:	GUN, MACHINE -  JAPANESE MACHINE GUN TYPE 1 (HO-103) ARMY AIRCRAFT 12.7MM SN# 9554
Maker/Manufacturer:	BROWNING, JOHN M.
Date of Manufacture:	04/01/1944
Eminent Figure:
Catalog Number:	SPAR 2545
Measurements:	OL:120.6CM 47 1/2" BL: 79.3CM 31 1/4"

Object Description:

JAPANESE MACHINE GUN TYPE 1 (HO-103) ARMY AIRCRAFT 12.7MM SN# 9554
Manufactured by Nagoya Army Arsenal (Yanazu Factory), Nagoya, Japan in 1944 - This type of Japanese weapon is recoil-operated, assisted by a muzzle recoil booster, air-cooled and belt-fed, right hand feed. 7-groove rifling with uniform left hand twist. Muzzle velocity of 2465fps. Cyclic rate of fire approximately 900rpm. Weapon weighs approximately 51 1/2" lbs. It is a remote-controlled fired machine gun of 12.7mm (.50 caliber), and is designed on the lines of the US Cal..50 Browning Aircraft Machine Gun, Model of 1921. This Fixed ACMG was officially assigned an "HO" (cannon designation) but receiver markings labels it a ACMG. Back plate won't closed. Various small parts missing.

Markings:
Receiver: Japanese characters/19.4 (April 1944 manufacturing date)/ Nagoya symbol/9554.

Weapon transferred to the Museum on 14 May 1947.

Web site photo is showing the business end of this gun.

Notes: "...6. For further compliance with O.O. 472/5/2848, the following information is submitted. a. Although designed on the lines of the U.S. Cal..50 Browning Aircraft Machine Gun, Model of 1921, the Japanese weapons presented several differences: b. The trigger assembly is so adjusted that the weapon may be fired from a closed bolt, or open bolt. These 'various' phases may be operated from remote control but change from one phase to another requires manual adjustment. c. Selective fire feed in not provided. Each gun is designed to feed from one side only. (Right or left) d. The Japanese weapons fire a smaller cartridge than the U.S. weapons....Therefore the receiver, bolt and main assemblies are smaller and non-interchangeable....7. Too much credence should not be given to interchangeability of parts between the U.S. and Japanese weapons of this type as there seems to be a loose fit one way or the other, and if many of the parts were interchanged, numerous malfunctions would result." - G.B. Jarrett, Lt. Col., Ord. Dept., Chief, Foreign Material Branch, April 24, 1943.

"Army Type 1 (HO-103) 12.7mm Fixed Aircraft Machine Gun (ACMG), sn 9554 - This Army Type 1 (HO-103) 12.7mm Fixed Aircraft Machine Gun (ACMG) was made at the Yanazu Factory of Nagoya Army Arsenal, in Yanazu-Mura, Hashima-Gun, Gifu Prefecture, Japan. Although this ACMG officially was assigned an 'HO,' or 'Cannon,' number by the Japanese, '1 Type,' appears in the gun's identifying markings which are located on the top cover plate of the receiver, at the rear. The first line of the receiver markings, nearest the feed cover, reads, '1 Type Fixed (Aircraft) Machine (Gun).' Immediately behind this marking towards the rear appears the single Kanji character 'Z,' or 'Otsu,' which indicates that the gun is equipped with right hand feed. Behind this mark appears the gun's manufacturing date, in this case, 'Showa 19.4,' or April, 1944. The Showa Era is the period of the reign of the Emperor Hirohito, which began in 1925. The number to the left of the period in the manufacturing date represents the manufacturing year with respect to the beginning of the Showa Era; the number to the right of the period in this date represents the month of manufacture. The manufacturing date is followed by the Nagoya Army Arsenal symbol, which represents two fabulous fighting fish positioned head to head within a circle, and which is derived from the feudal Nagoya Castle crest. The gun's serial number appears behind this symbol.
The Amory Type 1 (HO-103) 12.7mm Fixed Aircraft Machine Gun is essentially a Japanese copy of the air-cooled, belt-fed U.S. Browning .50 Caliber ACMG, although the Japanese gun exhibits obvious design differences from the Browning weapon with respect to cartridge used, firing modes, feed mechanism, and buffer mechanism. The Italian Breda 12.7mm x 81mm SR cartridge, also known as the .5 in. Vickers-Armstrong V/565, is used in the Army Type 1 (HO-103) ACMG, and this cartridge has a muzzle velocity of approximately 2500 feet per second, somewhat less that the 2850 feet per second muzzle velocity of the1 (HO-103) ACMG is charged by a hydraulic mechanism in its remote mountings, and is charged manually when close at hand. There is no provision for adjustment of the feed block to allow selective feed on the Japanese weapon, as there is on the U.S. Browning; each Type 1 (HO-103) ACMG was manufactured to feed from one side only. A disintegrating steel link feed belt was used. The adjustable oil buffer of the U.S. Browning is replaced with a spring-actuated buffer on the Japanese gun. A muzzle booster is employed to enhance the gun's cyclic rate of fire, which was estimated to be approximately 900 rounds per minute.
The Army Type 1 (HO-103) 12.7mm Fixed Aircraft Machine Gun was the mainstay of cowling or wing armament on many types of fighter aircraft used by the Japanese Army Air Force, but the gun appeared in the armament of bombers as well. Occasionally the gun was used in flexible mountings, contrary to its nominal purpose. The Type 1 (HO-103) ACMG appeared in the armament of the major types of Japanese Army Air Force fighter aircraft such as the Kawasaki Ki-61 Hein (Swallow), the Kawasaki Ki-100 Army Type 5 Fighter, the Nakajima Ki-43 Hayabusa (Peregrine Falcon), and the Nakajima Ki-84 Hayate (Gale).
In January of 1938 the design of the Japanese Army Type 1 (HO-103) 12.7mm ACMG originated in the Laboratory of Chuo Kogyo Kabushiki Kaisha, Ltd., in the Kokubunji Factory located in Hondashinden, Kokubunji-machi, Kitatama-Gun, Tokyo-To, and in December of that year a first model was tested. Initial production of the Type 1 (HO-103) ACMG did not begin at the Kokubunji Factory until 1940 however, and only 10 guns were produced in that year, according to company records. Presumably production of the gun was begun in the Yanazu Factory of Nagoya Army Arsenal at about this same time, but this presumption is yet unconfirmed by documentation or by actual guns specimens examined to date. Certainly by 1941 the Type 1 (HO-103) ACMG was in full scale production at both manufacturing sites and the gun was being installed regularly as principal armament in combat aircraft, even though the gun's design was not perfected. Testing and design development of the Type 1 (HO-103) ACMG began shortly after the design's inception by the Army's Air Technical Laboratory at Tachikawa and continued until war's end. As problems encountered with parts design and gun functioning were surmounted, they were replaced with problems caused by shortage of raw materials. Despite the many problems, meticulous field maintenance of the guns coupled with regular replacement of worn and fatigued parts made the Type 1 (HO-103) ACMG a successful design and an effective first-line weapon. U.S. Army interest in the Type 1 (HO-103) ACMG prompted testing of the weapon at Aberdeen Proving Ground and produced a comparative study of the Type 1 (HO-103) ACMG and the U.S. Browning .50 Caliber M1921 ACMG, principally to discern the interchangeability of parts between the two weapons. The study concluded that parts interchangeability was very limited and hence insignificant.
Company records of production of the Type 1 (HO-103) ACMG at the Kokubunji Factory of Chuo Kogyo Kabushiki Kaisha, Ltd. indicate that 14837 of these weapons were produced there between 1940 and 1945, but documented information about the Type 1 (HO-103) ACMG production at Nagoya's Yanazu Factory is not available. However, judging form serial numbers of Type 1 (HO-103) ACMGs examined, total production at the Kokubunji Factory of Chuo Kogyo K.K., Ltd. and the Yanazu Factory of Nagoya Army Arsenal are the only known manufacturers of the Army Type 1 (HO-103) 12.7mm Fixed Aircraft Machine Gun." - Professor Ed Libby, Ph.D.
"The Japanese were already using a 12.7mm Browning-type aircraft machine gun known as the '12.7mm Type 1 Machine Gun - Army.' With minor differences this weapon was similar to the early model of the US .50 caliber Browning machine gun. It fired at the rate of 900 rounds per minute, with a muzzle velocity of 2,500 feet per second." - Goldsmith, Vol. II.

"In the United States, during World War II, the development of the Browning short recoil action was limited to calibers up to .50, although the Browning long recoil type was manufactured in 37-mm bore. As a matter of interest, it should be noted that the Japanese thought so highly of the short recoil action that they adapted it to large calibers. Their 20-mm Browning gun was in very extensive use in the Pacific war. The action was also made in 30-mm and 37-mm sizes." - Chinn

References:
Chinn, George M. THE MACHINE GUN. Vol. III. Department of the Navy. Washington, D.C. 1953.
Goldsmith, Dolf. THE BROWNING MACHINE GUN: RIFLE CALIBER BROWNINGS ABROAD. Vol. II. Collector Grade Publications. Cobourg, Ontario. 2006.