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DEFINITIONS

ACCELERATOR
A device such as a pivot lever attached to a short-recoil assembly that increases rapid movement of the rearward action of the bolt for increasing cyclic rate of fire.

AIR-COOLED
The cooling of gun components by atmospheric radiation and circulation.

AUTOMATIC
A weapon which travels through a complete operating cycle continuously from a single function of the trigger without releasing it.

BARREL LINER
An inner sleeve inserted into the barrel to prevent rapid wear from friction and heat. An ordinary application would be on automatic weapons to increase barrel life.

BATTERY [IN BATTERY]
When all component mechanisms in a firearm are in their final position, [locked], ready for firing of the cartridge.

BELT FEED
A system for feeding ammunition into automatic weapons on a continuous basis. The belts may be a predetermined length or continuous depending upon the type of belt used. Original designs were two canvas strips stitched together to form open-ended pockets for the cartridges to slide into. Extraction of the cartridge from the belt was a method to withdraw it in a backward movement, raise or lower for alignment and finally pushed into the barrel chamber. The belt was advanced automatically for succeeding round positioning.

An improved design was canvas belting with metal clips attached to hold the cartridges in place. The open top clips allowed the round to be pushed directly from the belt into the barrel chamber by the weapon’s bolt thus eliminating some of the mechanism action.

A further advance system necessitated by usage of machine guns for aircraft was designed using ‘disintegrating links’. It was composed of individual metal clips or holders for each cartridge whereby the cartridges provide the linking function themselves. Its advantages did away with the cumbersome fabric belting with potential jamming of the material during the exit stage and the elimination of empty belt storage containers. The metal clips could be automatically discarded along with the empty shell casings from the aircraft. This system was also an advantage where long and continuous runs of belting were needed in remote locations of aircraft such as enclosed wing gun mountings.

BIPOD
A two legged support of usual attachment to gun barrel and used as an accuracy tool for long range targets and/or steadiness in sustained firing.

BLOWBACK ACTION
An automatic weapon which functions through the reloading cycle from use of discharge gas pressures acting directly on the fired cartridge and against the bolt retracting assembly for movement.

BLOW FORWARD ACTION
With the bolt in stationary position, the barrel moves forward from expanding gases to open the action and eject the expended cartridge case. As the barrel returns to battery, a live cartridge is loaded into the breech and ready for discharge.

BOLT [BREECH]
This term refers to the part in most automatic weapons which supports the cartridge case for injection, discharge and extraction from the barrel chamber. Containing the firing pin it moves horizontally to assist other moves in the functioning cycle. Sometimes referred to as a breech bolt it may be confused with the description of the term Breech Block.

BOLT LOCK [VERTICLE]
Also see ROTARY BOLT LOCKING.

The part of the firing mechanism located in the receiver, which holds the bolt in place and prevents movement during the moment of cartridge ignition. The lock positioned in slots in the receiver travels vertically and is controlled by motion of the gas actuator assembly. It is a feature of the Japanese Type 96 and Type 99 series of automatic weapons. Its end function is similar in results to the rotating type of locking system as found in the Lewis Machine Guns design.

BOLT LOCKING LUG[S]
Projections on the front or rear of bolt that cam into corresponding grooves in the barrel extension or frame to lock the bolt in battery position ready for cartridge discharge. The purpose is to hold the bolt in a steadfast and locked position during high gas pressures from cartridge discharge.

BREECH
The rear end of the barrel chamber where cartridge is inserted.

BREECHBLOCK
Similar to a bolt in function it supports the cartridge case in movement and may travel in any direction by pivoting or sliding perpendicular to the barrel bore axis. The most commonly known weapon utilizing the breech block system is the Vickers/Maxim family of automatic weapons.

BREECH LOCK
The mechanism which locks the breechblock into battery position.

BULLPUP [design]
A weapon, short in barrel and mechanism, in which the action assembly and/or cartridge magazine is located behind the trigger.

BUFFER
A resilient object located at the rear end of an automatic weapon’s recoil mechanism, which cushions the bolt in its rearward motion and generally prevents ‘shock’ recoiling of the action. The object may take the form of soft material, spring[s] or an air compression chamber all to provide smooth movement during recoil. Spring buffers can be so designed to assist in the speed of bolt return to its full forward position to increase the rate of fire. Additional resilience material can also be used to decrease the rate of fire.

CALIBER/CARTRIDGE DESIGNATIONS [metric]
Metric designation is in millimeters and indicate bore diameter and length of cartridge case. Example as the Japanese Arisaka cartridge, 6.5x50mm indicating the diameter as 6.5mm and the cartridge case length as 50mm. The designation may be followed by letters: R [rimmed], SR [semi rimmed].

CARTRIDGE CASE TYPES
For our purposes, cartridge cases are classified into 3 types. Rimmed, semi-rimless, rimless.
Rimmed. This type of cartridge has a protruding rim at the base which is several diameters larger than the case at its junction. The primary purpose is to serve as a shoulder for the extractor to rest against and “grip” for the cartridge removal from the chamber after firing. An example is the British .303 caliber ammunition.

Semi-rimless. This type of casing provides a cannelure, [extractor groove], around the base of the case allowing the extractor to grip the exposed rim base lowering extractor protrusion interference. The diameter of the base however is smaller than in front of the cannelure but larger than the rimless cartridge. The Japanese Type 92 heavy machine gun is designed to fire either their semi-rimmed or rimless 7.7 mm cartridge.

Rimless. The casing has a rim at the base with a cannelure at the junction of the rim for the entire circumference of the case. The rim generally has the same diameter or smaller than the case at its junction. Most modern small arms utilize the rimless cartridge case.

CLOSED AND OPEN BOLT SYSTEMS
Although each system has purpose of function, the open bolt system was necessitated with automatic weapon development. In general the development of cartridge firearms utilized the closed bolt system.

The closed bolt system in automatic weapons provided that when firing is interrupted by release of the trigger [or sear in fixed weapons], it allows the bolt to close with a live cartridge in the barrel chamber ready for trigger/firing pin release. Depressing the trigger allows the firing of the cartridge.

For the open bolt system when releasing the trigger interrupts firing, the bolt is held in its rearward position with a fully open chamber. When trigger is depressed the bolt moves forward picking up, chambering and firing a live cartridge without additional manual function. The open bolt system was considered essential in automatic weapons to leave an open chamber and allow air circulation for cooling. This was beneficial in preventing “cook off” or premature firing of a chambered cartridge in an overheated barrel. The major disadvantage of the open chamber was foreign material could gather, especially in lubricated areas, and cause jams, malfunctions and parts breakage.

COAXIAL [MOUNTS]
The mounting of a secondary gun, usually small caliber, next to and in parallel with a larger caliber primary gun, both on a single axis, concentrically with both weapons aiming in the same direction. Tank turrets often utilize this combination and purposely use the small caliber gun as a target spotter.

CONVERSION FACTORS
To convert millimeters to inches, divide by 25.4
To convert centimeters to inches, divide by 2.54
To convert grams to grains, multiply by 15.432
To convert grams to ounces, divide by 28.35
To convert kilograms to pounds, multiply by 2.2

COOK OFF
The reference to preignition of a cartridge in the barrel chamber generally caused by high heat absorption from the barrel. It was a common problem in early automatic weapon design, especially those firing from closed bolt position whereby a live cartridge is held chambered in a hot barrel. Eventually innovations such as water cooling, air cooling and open bolt positioning reduced the problem, however sustained firing of certain automatic weapons for an extended period of time will produce “cook offs”.

DEFLECTION
The projected angle between the position of a moving target and the required aiming, point, [lead], to accomplish contact.

DELAYED BLOWBACK
Related directly to automatic weapons it is a design condition where the bolt is not locked at the barrel for the duration of the bullet’s travel through the barrel until the chamber pressure has decreased. The system is basically a blowback principal with the added feature of slowing down the travel of the bolt during its opening movement. This feature may be any of several designs depending upon its needed function. Most common is a type of locking mechanism, which proceeds to unlock at recoil but delays total unlocking of the bolt. This feature has also indicated improvement of heat dissipation and lessens barrel temperature activity.

DISCONNECTOR
For most automatic weapons, this unit is part of the selective fire mechanism feature and may be sometimes confused with the sear. Its function is to disconnect the trigger from its attached mechanism upon a round being fired thereby preventing an additional round discharge without trigger positive function. Its purpose is to allow only one round fired with each function of the trigger. It is usually operated by a selector switch, which can function for single round or automatic operation.

EJECTION
The forceful mechanical action of discharging a cartridge, fired or unfired, from a firearm.

EXTRACTION
The first step in the forceful action of the extraction/ejection sequence by removing a cartridge from the barrel chamber.

EXTRACTOR
A spring loaded metal hook or claw, as part of the weapon’s bolt assembly, that engages the rim of a cartridge during its chamber seating. Its function is to withdraw the spent cartridge from the barrel during the rearward movement.

EXTRACTOR GROOVE
The groove at the base end of a cartridge next to the rim which provides for seating of the extractor.

FEED STRIPS
A system for feeding ammunition into automatic weapons. The strips, or trays, are generally of light metal that the cartridges are held into in a “clipped” fashion. The strips are fed into the weapon from either side determined by design necessity. Some designs were made of strips to be latched together for continuous feeding. The ammunition is stripped from the trays by the actuating system and fed into the barrel chamber. When all ammunition is emptied from the strip it is discharged thru the opposite side of the weapon.

FIRING CYCLE

The action order of an automatic weapon as [1] loading, [2] firing, [3] extracting, [4] ejecting, [5] reloading.

FLASH HIDER [SUPPRESSOR]
A device attached to the muzzle end of the gun barrel, which reduces muzzle flash but does not reduce muzzle blast. Not to be confused with “ muzzle brake” or “muzzle booster”.

FLEXIBLE MOUNT
A nonpowered gun mounting of which the gunner can move the weapon freely in vertical, [elevation], and/or horizontal, [traverse] direction.

FIRING PIN, FLOATING
A free traveling firing pin that is held in spring tension within the bolt and remains compressed until the live cartridge is in battery, then released by the sear/hammer assembly to contact the cartridge primer for firing.

FIRING PIN, FIXED
A nipple or bead that is milled into the face of the gun bolt and contacts the cartridge primer at the last moment of battery. The bolt itself under tension serves as the activator. The system is most common in “open bolt” firing automatic weapons. [Also see closed and open bolt systems].

FLUTED BARREL
Longitudinal grooves cut in barrel exterior to maintain rigidity during weight reduction, elimination of mass and increased cooling effect on automatic weapon applications. Reference: Italian Machine Pistol MP 38/42 series.

FURNITURE
In early firearms it was referenced as the metal components excluding moving parts and barrel. In recent times it is more referred to as the wooden elements of the gun.

GAS OPERATION
One of two popular methods to provide necessary mechanism operation of automatic weapons. [See also recoil operation]. The method is trapping and controlling a portion of exploding gas propellant from a ported barrel. The gas is directed into a cylinder containing a piston connected to the bolt assembly. The resultant pressure creates the movement for the reloading cycle.

GAS PORT [ORIFICE]
A small hole drilled into the underside and toward the muzzle end of the barrel which siphons off a portion of the fired cartridge powdered gases to the bolt connected piston for reloading cycle movement. For certain weapons the speed action is controlled by a variable sized hole “gas regulator” mounted at the end of the piston cylinder.

GAS REGULATOR
Automatic weapons in their rapid firing cycles are subjected to a variety of metallurgical changes of heat and friction which effect the operation. This coupled with ammunition variety performance requires a means of adjusting the reciprocating action of the bolt assembly for smooth performance under such conditions. The gas regulator is one of the items that provide such an adjustment. It is mounted into the piston cylinder with a series of holes sizes for rotary adjustment. The gases from the barrel gas port pass through one of the regulator holes to accomplish the function.

GRAVITY FEED
Ammunition is fed into the weapon’s mechanism by gravitation.

HEADSPACE, CARTRIDGE
A most critical dimension especially in automatic weapon mechanisms. Headspacing is generally termed as the distance from the face of the bolt or breechblock to the shoulder of the barrel where the cartridge case seats or that part of the barrel chamber that stops forward movement of the cartridge case. Headspace for rimmed cartridges is defined as the distance from the face of the bolt or breechblock to the face of the barrel. The distance for rimless cartridges is measured from the face of the bolt or breechblock to the front [upper shoulder] of the barrel cartridge chamber. Although critical this tolerance is very minute as measured in single digit millimeters.

Excessive headspace allows the cartridge not to be fully seated or to become unseated from the barrel during its ignition. The resultant is over expansion or bursting of the shell casing. Insufficient headspace may prevent the breechblock or bolt from fully seating in its forward position and prevent the locking mechanism from functioning causing the weapon not to fire. Over heating and metal expansion is a common cause of this condition where adequate means are not provided to compensate for the problem.

IGNITION
The igniting of cartridge propellant by its primer.

MACHINE GUNS, LIGHT, MEDIUM, HEAVY
The term “machine gun” in itself generally refers to an automatic weapon of less than 25 mm although some international references use 20 mm as dividing point between terms of gun and cannon.

The subject of classifying a machine gun as light, medium or heavy has been in controversy since machine guns were invented. Manufactures used the term as a tool in describing them for promotional purposes. Governments and military coined the terms as pertaining to weight and/or caliber. Each had a legitimate motive in their terms for classification however when automatic weapons became a worldwide industry, individual countries followed and maintained their own definitions without a common
boundary among the various nations.

European nomenclature used a method of classifying shoulder weapons with bipods as light machine guns. Tripod mounted small caliber machine guns were classified as medium machine guns and heavy machine guns were of a caliber larger than .45 and generally considered in the 12.7- 13.2 mm class.

The United States labeled the shoulder; bipod mounted Browning BAR as an automatic rifle; [The French called theirs a machine rifle]. Bipod or tripod mounted air-cooled small caliber weapons were known as light machine guns. Small caliber water-cooled and the .50 caliber water and/or air cooled were termed as heavy machine guns. All of these definitions were not without exception.

It is difficult to standardize on a universal definition for each category, as the caliber vs. weight is a contradiction in itself when comparing automatic weapons by their true nomenclature from different countries. An example is of the Model 1900 series of Hotchkiss machine guns. It was termed by the using European countries as a heavy machine gun although the calibers were in the 8mm range. When the Japanese started producing the weapon in Japan and in the smaller caliber of 6.5mm they continued the term use of heavy machine gun thusly setting a technical nomenclature pattern based on weight. This continued throughout their army’s development of automatic weapons even with caliber sizing changes. Bipod, tripod, shoulder fired, caliber sizing was so diversified in their army’s weapon armament only a few types were formally categorized. The designations, which have been previously recorded, are generally terms labeled by the United States and allied nations for identification purposes.

For purposes of these works the usage of terms to categorize a certain machine gun is of formal Japanese identification and those not categorized will be described in detail in a manner to identify the intended purpose.

MACHINE [AUTOMATIC] CANNON
Automatic weapons in the 25mm to 40 mm are generally classed as automatic or machine cannons.

MACHINE PISTOL
An automatic weapon which in general terms utilizes pistol or revolver ammunition.

MAGAZINES See Chargers, Clips and Magazines

MUZZLE BOOSTER
A device attached to the muzzle end of the barrel, which utilizes the explosive discharge gases for a more rapid movement of the recoil mechanism during the mid portion of the firing cycle to increase the rate of firing.

MUZZLE BRAKE
A device attached to the muzzle end of the barrel so designed as to deflect a percentage of the propellant gases in a variety of direction to lessen the recoil shock.

OPEN BOLT SYSTEMS See closed and Open Bolt Systems.

RATE OF FIRE
The timed repetition of firing between rounds in automatic weapons. Usually described in and referred to as rpm.

RECEIVER [FRAME]
The main body of a firearm that contains the operating mechanism of which the barrel and stock, if any, are attached.

RECOIL OPERATION
A common system for controlling the cartridge movement of automatic weapons. [See also gas operation]. This method utilizes the cartridge propellant explosion pressure to drive the shell casing rearward against the bolt forcing it rearward sufficiently to eject the spent round and reload the next round into the chamber. The combination of recoil spring pressure and chamber pressure drop timing provides bolt travel at a controlled speed and smooth rate.

ROTARY BOLT LOCKING
Also see Bolt Lock.
The rotating of a bolt in position to a barrel extension or forward portion of the receiver to lock it in place for firing of the cartridge.

ROTATING MOUNT See flexible mount.

ROUND
A single cartridge of ammunition.

R.P.M. Rounds/revolutions per minute.

SEAR
The sear, as part of the firing mechanism is the unit linked between the trigger and the bolt, firing pin assembly or hammer, which under spring pressure, moves clear by trigger function and allows discharge of the round.

SELECTIVE FIRE
The means in which a full automatic weapon that fires continuously with a depressed trigger, can be changed by a lever control to fire only one round each time the trigger is depressed.

SEMI-AUTOMATIC [autoloading, selfloading]
A weapon which travels through a complete operation cycle each time the trigger is depressed.

SUB-MACHINE GUN See Machine Pistol.

SYNCHRONIZATION
An automatic weapon with a timing system adapted to fire between the rotating propeller blades of piston driven engine aircraft.

TYPE OR MODEL
The character is found on many Japanese ordnance items of various descriptions from handguns to cannons. There has been controversy for many years among language students and military collectors as to the proper English designation of either model or type.

The Japanese character is written as Shiki. According to Japanese-English translation dictionaries of the World War II era, among other definitions it includes the English word model without the mention of type. A 1942 “Dictionary of Military Terms” translates Shiki into meaning type or model. The dictionary’s English translation for the word type is Shiki, however the word model does not mention Shiki in its definition. The character Kata is shown in both the English definitions and defined as type, pattern, mark, model.

An English translation of a manual published by Nagoya Army Arsenal in April 1940 refers to the subject: as Model 94 Pistol. Translation date is unknown. The Office of the Chief of Ordnance, Washington D.C. in their publication of August 1945, “Translations of Japanese Ordnance Markings” uses the Shiki word as type and states: “Only one character is used to indicate type classification. “ This character is ‘Shiki’. It appears on artillery shells, bombs, small arms, howitzers, fuses, etc”…. However in their table of type designation using the word Shiki, they translate it as model and again in their table of numbers Shiki “meaning is model”. The “Handbook on Japanese Military forces” War department [U.S.] Technical Manual TM-E-30-480, October 1944- September 1945 in the equipment section refers mostly to ordnance items as models such as the Model 96 and 99 light machine guns. The section on weapons however refers to them as types. This includes small arms, cannon, artillery, ammunition and heavy armored equipment. The book “The Machine Gun” by Lieutenant Colonel George M. Chinn in volume 1 refers to the Japanese Weapons as types, and in the same section refers to the same weapon as models. The photo captions also refer to them as models.

The Government Technical manual TM-E-30-480 in the communication equipment section refers to model as the basic designation of an item and type for its secondary usage such as “Model 94, Type 1 Transmitter”. The Department of the Army [U.S.] Technical Manual, FM 9-1985-4 of March 1953, includes type as the basic designation and model as the secondary usage. Example: Type 100 Model 2, 20-mm.

To trace the history through some chronological order it would be of benefit to observe a published history of firearms from an early start through conversion to the apparent common usage of type as the proper and generally accepted translation of the character Shiki. Perhaps the most common known works is “Small Arms of the World”, by W.H.B. Smith who started with his first book in 1943. His forward does reference closeness with U.S. military and other foreign manuals. When referring to a firearm the term model is used such as the Model 94 pistol. The 1948 version of the book refers to all of the firearms in the Japanese section with number designations as models. By 1973 the tenth edition lists all weapons from handguns to machine guns as types with the appropriate number designation. The author’s note in the 1943 edition mentions briefly the Japanese method of weapon identification “by class name” followed by the adoption year associated with a particular emperors reign. An example is cited of the Ariska rifle adopted in 1905 and called the “Year” or “Pattern” 38. These same comments continue through the 1948 fourth edition.

It is apparent the term model was first used in the identity of ordnance especially firearms. The western world long before the Japanese involvement of firearms had identified firearms with the term use of model. Major world powers such as France, Germany, Italy, Russia and the United States used the term as a primary identification of firearms. The one major power exception was Great Britain, who chose to follow their long-standing tradition of utilizing the Roman term of Mark.

To add some meaning to the historical significant of usage reasoning requires some background of the Japanese introduction and involvement in their firearms history. In 1859 a reoccurring movement introduced foreign sources of firearms to Japan. Their first adoption in 1880 was firearms from western countries of France, Germany, Great Britain Holland, Russia, Portugal, and the United States, some with and some without a primary identity other than style of firearm and year of public appearance. Those firearms sourced with a particular system used model as the primary identification such as the model 1873 Winchester rifles supplied by the United States.

It follows that in keeping identity with foreign designation of firearms the first Japanese produced firearms in their arsenals in 1880 was termed the Model 13 rifle and continued with the Model 22. By 1895 when the first Magazine-fed rifle began production at Koishikawa Arsenal, it was officially designated as the Type 30 infantry rifle. In 1893 after importation of large quantities of Smith & Wesson Model series of Russian revolvers, Japan’s Koishikawa Arsenal started production on an S &W patterned revolver. It was officially designated as Type 26. These appear to be the first of indications by the Japanese using the official term type in their firearm designations.

An additional example in transition of identity is Japan’s use of the Model 1900 Hotchkiss Machine Gun manufactured by the Hotchkiss firm of Paris, France. The Japanese used the Model 1900 extensively in the Russo-Japanese War of 1904-1905. Then under a license agreement with the Hotchkiss firm they started production in 1914 in their own arsenals with their own version and officially designated it as the Type 3.

The Imperial Japanese Navy in their ordnance designations used type and model for separate meanings starting in the 1920’s and continued with it through World War II. Type followed with a year designation was used to identify the weapon itself as in Type 92. When inscribed on a weapon, model indicated a permanent change to the gun such as removing, adding in the casting or machining process or modifying with die changes. An example, as in Model 2. This meaning should not be considered the same as the term modification as they are two separate identities. Modification indicates a nonpermanent change such as various attachments; ammunition feed positions and conversions for specified usage.

It is apparent that the Japanese Government with arsenal development and production had decided upon a term separating their own designed and manufactured firearms from those of foreign adoption in previous years. If this was the intent it had taken a long time to obtain acceptance of the specific term as its many years of warring during the growth period caused confusion and prevented widespread recognition. Perhaps translators have contributed most to the problem, as their interpretation is just that.

For purposes and standardization in these works, unless otherwise noted, type will be the prime designation with model as secondary where the two terms require symmetry in describing a series of changes.

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