Home      ARTICLE: JAPANESE TYPE 96/99 LIGHT MACHINE GUN BOLT LOCKING MECHANISM/SYSTEM
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TYPE 96 LIGHT MACHINE GUN, [Kyuroku Shiki Keiki], first produced by Kokura Army Arsenal, [Kokura Rikugun Zoheisho], in 1938.  The arsenal produced some 8,600 guns by March 1943 then converting to the newer Type 99 Light Machine Gun production.
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FORWARD:  There has been controversy for many years by various authors regarding the characteristics of the Type 96 light machine gun being duplicated from various foreign designs verses development from Kijiro Nambu original patterns.  Certain refinements and concepts however differ sufficiently for the weapon system to be classified as an original design rather than copied.  One such disputed example involves the controversy of the bolt locking mechanism whether a Nambu original or of Russian source as claimed in certain published works.  The following is a chronicle in sequence of the development/acceptance period, its purpose and background history.

AUTHOR’S PREFACE: The locking of the gun’s bolt to restrain the cartridge from rearward travel into a malfunction phase is described in Charles E. Balleisen’s 1945 book, PRINCIPLES OF FIREARMS.  Described as the “obturating” phase of the operation, he describes this function as…..”to have the bolt remain stationary while a separate member, known as the breech lock, moves laterally to engage both the barrel and breech members.” From Russian, English and allied translations, a variety of terms have been used in description of this system since it surfaced in the late 1920’s.  The Japanese term for the part itself is senshi” and translated as ‘bolt lock’ by Creswell-Hiraoka-Namba in their DICTIONARY OF MILITARY TERMS and McLaren Company’s reprint of A DICTIONARY OF MILITARY TERMS AND APPENDICES.  Throughout these works, I have used the term BOLT LOCK to coincide with this translated designation.

After the Japanese-Russian war and Portsmouth Peace Treaty of June 1905 a commerce relationship developed between the two countries.  Between 1914 and 1916 Russia purchased thousands of Arisaka rifles from Japan.  In February 1916 an agreement was reached whereby the Japanese Government agreed to purchase Russia’s Yen-based Sovereign Debt papers and also accepted a second bond issued in September.  Trade agreements were enhanced. In December, Japan’s High Army Command established the Military Exchange and Procurement Mission, and directed them on a fact finding expedition of various armament preparedness to Russia, England and European countries.

Colonel Kijiro Nambu, Chief of the Rifle Division, Tokyo Arsenal, headed the delegation. Leaving on December 3, 1916, they reached Manzhouli, Russia on December 9.  Continuing on to Leningrad on December 17 they were met by embassy officials and representatives of Mitsui, Mitsubishi and Takada, private companies involved in international armament trading.  [This group would eventually earn the title of “Merchant of Death”.]  They toured several production facilities including a rifle manufacturing factory and an ammunition producing facility.  On December 27 they left the capital and continued their journey through European countries and England then returning to Japan in late May 1917.

Mr. Kijiro Nambu, a Captain in the Imperial Japanese Army, began his career in firearms concepts during his assignment to the Koishikawa Arsenal in 1897 and proceeded to become involved in ordnance of small arms design for some 48 years terminating at the end of World War II.  His beginning pistol design evolved in the early 1900’s with the first specimen in 1902. During the following years he presented additional pistol/revolver developments for military and commercial distribution.  In 1927 his  pistol, designated Type 14 was adopted by the Imperial Japanese Army and remained a standard issue until the end of World War II.
 


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TYPE 14 PISTOL of Kijiro Nambu design, adopted by the Imperial Japanese Army in 1927 and issued to non-commissioned officers.  It was produced by his company, Nambu Rifle Manufacturing Company and Nagoya Army Arsenal. 
 
 
 

 
 
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Furthering his pistol research development, Mr. Nambu, was granted Japanese patent #89045 on November 26, 1927. It presented a different configuration in his semiautomatic pistol design from the Type 14 pistol.  A feature which followed both European, [Mauser], and American, [Savage], designs was the recoil feature which encompassed a spring system that surrounded the retracting barrel for reflex movement control.   A locking feature utilized a type of block in vertical movement and locked the barrel from movement when in battery position.
 

 
 

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PATENT NUMBER 89045 granted to Kijiro Nambu on November 27, 1927. It was the precedence for development of his Type 94 semi automatic pistol. This view shows the systems in battery, with locking feature in place and ready for cartridge discharge.

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In 1929, Mr. Nambu began development on a downsized pistol from his currently produce Type 14 in production for the Army at the time.  He had been approached by the Japanese Army to design a handgun of smaller configuration for their Air Force aviators and other military personnel such as paratroops and tank crews that would dwarf the Type 14.  Prototypes in 8mm caliber were completed in 1931 but were only minimal in size reduction.  Development continued under army ordnance guidance of a pistol with emphasis for officer usage.  From 1931-1934, prototypes were created and tested.  A final version was accepted by the Imperial Japanese Army in 1934 and put into production in June 1935.  It was designated as the Type 94 pistol.

 

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TOP PHOTO: Type 94 pistol, [1934], developed from Mr. Nambu’s patent #89045.  It was a major design change from his Type 14 pistol that followed certain European and  American patterns. 
 
 
BOTTOM PHOTO: Parts identification; 1: Slide. 2: Bolt. 3: Firing Pin. 4: Firing Pin Retainer. 5: Barrel Bushing. 6: Barrel. 7: Receiver. 8: Locking Block, [bolt lock]. 9: Recoil Spring. 10: Grips. 11: 8mm Cartridge. 12: Magazine.
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The new pistol retained his patent design feature of the recoil spring surrounding the barrel and its locking mechanism using the vertical block design.  To sequence its action the locking piece moves freely within slotted guides which is part of the barrel and located under the cartridge chamber portion.  When the barrel/slide assembly is in the final stage of battery position, the lock is directed upward by two notches located on the bottom of the slide contacting cutouts in the frame and locking the assembly in place ready to fire.  After cartridge discharge, the assembly moves rearward approximately 5mm forcing the lock downward sufficiently enough to allow the slide to continue its rearward movement for the chore of cartridge extraction and hammer cocking.  Reverse movement is actuated by the compressed recoil spring moving the slide forward to chamber a new cartridge and actuate the locking mechanism to complete the cycle.

In 1929 the “Manchuria Incident” occurred as a result of a confrontation between Chinese and Japanese troops at the South Manchuria Railway which continued with the Japanese occupying the city of Shanyang and escalating clashes between the two groups.  The Japanese had encountered a new machine gun, the Model ZBvs26, used by the Chinese who purchased them from Czechoslovakia and eventually produced their own version as the Type 41 light machine gun.  Captured specimens in the 7.92mm caliber were forwarded to Japan’s Army Ordnance Department for evaluation.  Favorability of the weapon’s performance prompted a new development in the light machine gun class away from the current Type 11 hopper fed light machine gun of Hotchkiss design.      

In June 1931 Mr. Nambu began development on a new light machine gun at the Koishikawa Army Arsenal by order of the Minister of the Army. Specifications were prepared by Japan’s Army Technology Headquarters.  Among the primary design parameters were: 6.5 mm caliber, weight under four kilos, box type magazine, interchangeable barrel, portability, spent cartridge ejection course, drum type rear sight control and provision for use of an oil container for cartridge lubrication. Mr. Nambu in his autobiography wrote: “In response to these requirements, our factory’s design, in order to reduce weight as much as possible, shortened the mechanism as much as possible by using a special bolt lock to connect the bolt and receiver. This enabled us to make the bolt itself extremely short.  Because we used this special type of bolt lock, a piston check mechanism was added.  As the bolt completes the loading of the cartridge into the chamber the piston alone again moves forward lowering the bolt lock.  This is a new design for securing the bolt to the receiver.” [Author’s note:  The “piston check mechanism” in Mr. Nambu’s quote refers to the gas piston operating rod as referenced in translation document No. 57, ENEMY PUBLICATIONS, REFERENCE MANUAL TYPE 96 LMG, 30 SEP 41 by the Allied Translator And Interpreter Section, South West Pacific Area, General Headquarters, United States Army].

Design invitations were also sent to Tokyo Gasu Denki Kogyo KK, [Tokyo Gas & Electric Company], andNippon Tokushu-ko KK, [Nippon Special Steel Company]. During the initial trials specimens submitted by the Tokyo Gas & Electric Co. and the Nippon firms were eliminated primarily because of high firing rate and the unresolved controversy of lubrication needed for adequate primary cartridge extraction.  In the final testing the Nambu design was accepted over an original arsenal submission.

 



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CROSS SECTIONAL of Type 96 Light Machine Gun developed from Mr. Nambu’s application on February 6, 1935. Patent #112691was granted on October 10, 1935. This view was taken from the weapon’s manual illustrating the action in battery position. 

 
 
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The accepted design included similar features of the Czechoslovakian Model 26, Light Machine Gun and the British Bren gun.  The method of bolt locking did not follow the Czech weapon design, which utilized a tilting feature which proved disadvantageous during sustained firing by distorting barrel accuracy.  Mr. Nambu’s design was a squared hollow piece which the gas/piston rod passes through, serving to control the locking piece. The bolt lock’s uniqueness prompted Mr. Nambu to patent the concept.  Patent #117662 was issued on March 30, 1936.  The patent also included a sear safety lock to prevent functioning of the sear if the bolt lock is not fully seated in place when the action is closed and ready to fire the cartridge.

 Some additional features of the Type 96 light machine unique in concept and function were the bolt assembly, barrel locking system and trigger mechanism.



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EXCERPTS from patents 112691 and 117662. 
 
RIGHT PHOTO shows the bolt lock and sear safety bar. 
 
 
LEFT PHOTO illustrates from accompanied explanation, the gas piston operating rod/bolt lock/firing pin relationship with the top figure showing the assembly in battery position.

 
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The sequencing of the Type 96 Light Machine Gun operation from the open bolt position, starts with pull of the trigger, allowing the gas/piston operating rod and bolt assembly to move forward while stripping a loaded cartridge from the magazine. As the bolt reaches near the “in battery” position, the bolt lock, guided by slots in the receiver frame is moved upward by a beveled ramp on top of the operating rod, into a slot in the bottom of the bolt, locking it in place with the sear safety bar proofing the position. After cartridge discharge, vented gas pressures force the bolt/operating rod rearward.  As pressure drops during minute free movement, the bolt lock is forced downward by a beveled ramp on the bottom of the operating rod, delatching the sear safety bar.  The bolt/operating rod assemblage continues its rearward travel performing extraction and movement to the full open bolt position ready for trigger action to start a new cycle.

The bolt lock system was also incorporated into the new 7.7mm caliber Type 99 light machine gun system which went into production in 1940. In late 1944 towards the end of World War II production the sear safety bar was eliminated, followed by the bolt lock mechanism in its entirety.

In Russia, Vladimir Grigorevich Federov, a graduate of their Military Artillery Academy, in 1905 converted a bolt action Mosin rifle to automatic mode.  A prototype was manufactured at the Sestroretsk small arms factory followed by a second version in 1912.  Neither was adopted, however the Model 1912 version continued in further development and by 1913 experiments began with the Japanese 6.5mm cartridge.  In 1916 the improved model featuring selective fire was accepted for production in the Japanese caliber.  It was titled the Federov Avtomat.

Sergei Gavrilovich Simonov in 1917 became employed as a mechanic assembling the Avtomat assault rifle at the Sestroretsk factory.  Graduating from Moscow Higher Technical School in 1924 he became an ordnance inspector at the Tula Arms Plant in 1926.  He later became the head of the prototype shop at the Federov design bureau involved in evaluating various designs of automatic rifles for acceptance into the military. He was accepted as a member in the Communist Party in 1927.

 


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SERGEI GAVRILOVICH SIMONOV’S Model AVS36 automatic rifle, the first of his designs was accepted by the Russian Military in 1937 in caliber 7.62x54R. Only about 1000 were produced before the military replaced it with the Tokarev Model 1940 assault rifle. 

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In 1930 he completed a prototype weapon which would be accepted by the Red Army in 1937 and titled AVS, [Avtomaticheskaya Vintovka Simonova….Automatic Rifle Simonov]. The weapon was gas operated, selective fire and loaded from a 16 cartridge capacity magazine.
 


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MODEL AVS36 CROSSECTION shown in battery position.  The bolt locking mechanism has similarity with the Japanese Type 96 Light Machine Gun’s bolt locking system.

 
 
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