HomeARTICLE: JAPANESE TYPE 96/99 LIGHT MACHINE GUN BOLT LOCKING MECHANISM/SYSTEM
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.
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.Tradeagreements
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.
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.
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.
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.
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.
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.
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 forevaluation.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 arsenalsubmission.
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.
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.
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.
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 rampon 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.
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.
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.
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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ARTICLE: JAPANESE TYPE 96/99 LIGHT MACHINE GUN BOLT LOCKING MECHANISM/SYSTEM
