by Anthony G Williams

This is adapted from Rapid Fire: The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces and Assault Rifle: the Development of the Modern Military Rifle and its Ammunition


AA anti-aircraft
accelerator a pivoting lever inside a short-recoil mechanism which acts to accelerate the rearward movement of the bolt
ACR advanced combat rifle: a competition held in the USA in the late 1980s

ACSW Advanced Crew Served Weapon (formerly OCSW); US 25mm AGL, designated XM307

AGL automatic grenade launcher (aka GMG)
AHEAD Advanced Hit Efficiency and Destruction (a proprietary Oerlikon ammunition development)
air-cooled a weapon which achieves barrel cooling by radiation direct to the atmosphere
ammunition collective name for cartridges (or equivalent)
AP armour piercing; a projectile designed to penetrate armour, or a cartridge loaded with such a projectile
APC(BC) armour piercing, capped, (ballistic capped): an AP shot with a softer cap to aid penetration of face-hardened armour (and a streamlined cap to reduce air resistance)
APCR armour piercing, composite, rigid: shot consisting of a penetrating core (usually of tungsten alloy) enclosed within a light-alloy body, which travels as a unit to the target
APDS armour piercing, discarding sabot: similar to APCR except that the body (which may be light alloy or plastic) breaks up and falls away from the penetrating core when the shot leaves the muzzle.
APFSDS armour piercing, fin stabilised, discarding sabot: similar to APDS except that the penetrating core is long and narrow and is stabilised in flight by fins
APHC armour piercing, hard core: an alternative designation for APCR
APHE armour piercing high explosive
APHHW All-purpose hand-held weapon: USA project 1959-62

API armour piercing incendiary: a dual-purpose projectile
API blowback advanced primer ignition blowback: a type of automatic mechanism
APSV armour piercing super velocity; British term for Littlejohn squeezebore ammunition (also initially used to describe APDS)
arrowhead shot APCR with reduced-diameter alloy body in centre
assault rifle a military rifle offering selective fire (both full and semi-automatic) with an effective range of at least 300 metres, and normally firing a cartridge intermediate between pistol/SMG rounds and full-power rifle/MG rounds of 7.62mm (or similar) calibre

AT anti-tank
automatic a weapon which continues to fire and reload automatically for as long as the trigger or firing button is pressed

B added to a cartridge designation to identify a belted case (e.g. 20x105B)
ball (round) a small arms projectile or bullet, i.e. not AP, I, HE, or T
ballistics the science concerning the passage of a projectile from the instant of firing to the end of its flight
ballistic cap a streamlined (usually light alloy) nose cone used to improve the ballistic coefficient of a blunt projectile
ballistic coefficient a factor which measures the aerodynamic drag of a projectile and therefore the rate at which it loses the velocity: the higher the number, the lower the drag
barrel the tube connected to (or integral with) the chamber, down which the projectile is accelerated
barrel extension the part of the barrel which extends behind the chamber, usually to accommodate a locking mechanism
base bleed a projectile which contains a slow-burning chemical in the base in order to reduce air resistance and extend range
base fuze a detonating fuze fitted to the base of an HE shell
battery a gun is "in battery" when it is at rest in a forward position in the mounting (i.e. not recoiling)
bayonet-a short knife or spike for fitting to a rifle barrel; it may be detachable or folding

BB see base bleed
BC ballistic coefficient: an indicator of the aerodynamic efficiency of a cartridge

belt (1) a raised strip around a cartridge case, in front of the extractor groove. (2) a strip of fabric or (more usually) metal, into which cartridges are fitted to facilitate feeding them into a weapon. Metal belts may be disintegrating, non-disintegrating or a continuous loop
belted case a cartridge case with a raised section in front of the extractor groove to aid location in the chamber
belt feed the use of a belt to supply ammunition to a gun mechanism
belt link a piece of metal which constitutes a part of a belt
bipod a two-legged support fitted to the forward end of a gun, for accurate firing in a prone position

BK Bordkanone (German): a large-calibre airborne cannon
blank a cartridge which has a primer and propellant but no projectile
blowback a type of automatic weapon operating mechanism
bolt a part of the operating system, containing the firing mechanism, which slides in line with the barrel, pushing a cartridge into the chamber and holding it there during firing
bolt carrier part of the action, which contains the bolt and reciprocates with it. It begins to move before (and finishes moving after) the bolt because its task is to unlock and lock the bolt to the barrel

bolt group the bolt assembly, including the firing pin/hammer and other items which are attached to the bolt

bolt lugs protrusions from the bolt, which are used to lock it to the barrel extension or receiver

bolt stop the part of the receiver which stops the bolt's rearwards movement

bore the inside of the barrel
bottlenecked cartridge a cartridge with a case whose diameter reduces sharply to the neck, creating a shoulder
bourrelet shell bodies are usually made slightly smaller than the bore, except for a slighter wider part which is carefully machined to fit - this is known as the bourrelet

box magazine a type of magazine in which the cartridges are stacked on top of each other (they may be single or double stacked)
Brandgranate (German): incendiary shell
Brandspreng-granate (German): high explosive/incendiary shell
breech the opening at the rear of the chamber which allows cartridges to be loaded and fired cases extracted
breechblock alternative term for bolt, normally used when its operating movement involves pivoting, or sliding vertically or horizontally
breech face the part of the barrel surrounding the breech
BRL Ballistics Research Laboratory: at US Army, Aberdeen

bullet see ball
bullpup design a rifle in which the action and magazine are behind the trigger
burst fire a control which fires a defined number of rounds (usually two or three) for each press of the trigger

butt the back face of the rifle, which is held against the shoulder on firing

buttstock the back part of the rifle, from the receiver to the butt

calibre (1) the diameter of a projectile, or of the inside of a barrel. (2) designation of the cartridge a weapon is designed for
calibre length the barrel length divided by the calibre, usually prefixed with "L"; e.g. a 40mm L/70 indicates a barrel (40x70=) 280 cm long
cannelure a groove around a small-arms bullet for receiving a crimp
cannon (modern) a large-calibre fast-firing automatic weapon, generally taken to be between 20mm and around 57mm calibre
cartridge a unit or round of ammunition, normally comprising the cartridge case, projectile, propellant and primer
cartridge case the part of the cartridge which contains the propellant and holds the projectile and primer firmly in place
caseless ammunition ammunition which does not have a cartridge case but uses solid propellant to hold the projectile and primer
centrefire cartridge fired by a primer located in the centre of the head
chain gun an externally-powered automatic weapon which uses a chain to drive the operating cycle
chamber the space at the rear of the barrel in which the cartridge is positioned and supported during firing
chemical fuze a contact fuze on an HE shell which operates by percussion
chromium plating used to protect the barrel bore and chamber
CIWS close-in weapon system; a naval short-range AA/anti-missile system, usually with automatic aiming and firing
clip a piece of metal which holds together several cartridges (normally by the case heads) for feeding into a weapon; or several cartridges held together by a clip
closed bolt an automatic weapon designed to commence the firing cycle with the cartridge already loaded into the chamber (see open bolt)
closed loop a CIWS control system which uses radar to track both target and projectiles and corrects the aim accordingly
coaxial mounting a means of mounting a secondary gun in parallel with a primary gun so that both weapons can be aimed using the same sights
combustible case a cartridge case which is designed to burn with the propellant
compensator a type of muzzle attachment for hand-held weapons, in which all of the diverted gas is directed upwards to resist muzzle rise

contact fuze a fuze which is initiated by impact with the target
cook-off the unwanted ignition of a cartridge by heat in a gun chamber
cordite a type of propellant
counter-recoil a type of gun mounting in which the gun is fired as it returns to battery, so the initial recoil force is expended in arresting the forward movement of the gun. See floating mounting and soft recoil
cowling mounting an automatic weapon mounted in the cowling of a propeller-driven fighter and synchronised to fire through the propeller disc
CQB close-quarter battle: especially urban fighting

crimp a depression in the neck of a cartridge case, intended to hold the projectile firmly in place prior to firing
CTA cased telescoped ammunition: in which the projectile is contained with the cartridge case (which is often combustible)

dark trace the initial burn of a tracer, designed to give no light
deflection the angle between the position of a crossing target (usually an aircraft) and the required aiming point, which will be ahead of it
delayed blowback a hybrid gun mechanism in which the bolt is locked to the barrel on firing, is then unlocked by the mechanism, but relies on blowback for the remainder of the firing cycle (see retarded blowback)

detonation the explosion of an HE projectile
dioptre sight (American - 'diopter') a type of rearsight which provides a small hole through which the shooter looks at the foresight

disintegrating link a type of ammunition belt consisting of metal links, which fall apart as each cartridge is chambered
double base a type of propellant
drill round a cartridge which is totally inert, used to practice loading and unloading drills. It is always made easily recognisable
driving band a strip of soft metal or plastic around a projectile, which is intended to be gripped by the rifling in order to induce spin
drum a type of circular magazine in which the cartridges are held parallel to each other (sometimes used to describe a pan magazine); see helical drum and pan magazine.
DU depleted uranium; a heavy metal used in some AP shot
dual belt feed a gun with two belt feeds, each usually loaded with a different type of ammunition
dummy round a cartridge which is completely inert (i.e. no primer or propellant)
duplex loading a cartridge loaded with two full-calibre projectiles, intended to follow each other down the barrel (see multiball, triplex)

ejection the act of throwing an extracted cartridge case clear of the gun
electric ignition a method of igniting cartridges by passing an electrical current through the primer
electromagnetic gun a gun which uses electromagnetic force to accelerate a projectile (also known as a rail gun)
electrothermal-(chemical) a system which uses a plasma generator instead of a primer
elevation the movement of a gun in its mounting through a vertical arc
ER extended range
ERFB(BB) extended range, full bore (base bleed)
erosion wear on the inside of a barrel caused by hot propellant gasses and friction generated by projectiles
external or exterior ballistics the science of projectile flight from the muzzle of a gun
extended chamber see hooded chamber
externally powered a gun mechanism which requires an external source of power to operate; this is usually electric but may be hydraulic or manual, or in aircraft powered by engine gas or the slipstream
extraction the act of pulling a fired cartridge case from the chamber
extractor claw a hook, attached to the bolt, which fits into the extractor groove in order to pull the cartridge out of the chamber
extractor groove a groove around the head of a cartridge case, into which the extractor claw fits

FABRL USA ammunition project: originally Frankford Arsenal + BRL, then 'future ammunition for burst rifle launch'

FAPDS frangible armour piercing discarding sabot
feed the method of delivering ammunition to the gun
FCAR full-calibre assault rifle; one firing an intermediate cartridge with a calibre the same as a full-power rifle/MG round (i.e. 7.62 or 7.92 mm)

feed the method of delivering ammunition to the gun

FGB Flächengondelbewaffnung (German) an aircraft gun pod
fin stabilised a projectile whose flight is stabilised by fins rather than by being spun by rifling
firing cycle the sequence of loading, firing, extracting, ejecting and reloading
firing pin a spring-loaded steel pin which strikes a primer to cause ignition
FlaK Fliegerabwehrkanone (German) AA artillery; also sometimes given as Flugabwehrkanone or Flugzeugabwehrkanone
flash hider a cone-shaped device fitted to the muzzle to screen the muzzle flash from the firer

flash suppressor a device fitted to the muzzle to reduce the flash from burning propellant

flat trajectory the flight of a projectile which involves minimal drop due to gravity; associated with high velocity
flechette a long, thin bullet, which is fin-stabilised and (in small arms) contained within a sabot for firing

flexible mounting a simple, unpowered gun mounting in which the gun can be moved in traverse and elevation by the gunner's hands
floating firing see counter-recoil
floating mounting see counter-recoil
fluted chamber longitudinal grooves in the chamber to permit gun gas to seep back around the cartridge case to prevent it from sticking
FMPDS frangible missile-piercing discarding sabot
folding stock a buttstock which is can be folded to lie alongside the rifle

fore grip-the grip under the barrel for the forward (non-firing) hand

FPAR full-power assault rifle; a selective-fire rifle chambered for the 7.62 x 51 NATO or other full-power rifle/MG cartridge

fragment when a bullet breaks up under the stress of impact and tumbling it is said to fragment

frangible a projectile designed to break up on hitting the target
full-calibre a projectile which fills the bore of a gun (see sub-calibre)
fuze a device for initiating the detonation ofn an HE shell

gas operated a type of gun mechanism using gas tapped from the barrel to drive the firing cycle
gas regulator a valve on a gas-operated weapon which regulates the amount of gas tapped to operate the action, according to circumstances

gas-unlocked blowback a type of gun mechanism using gas tapped from the barrel to unlock the breechblock; the remainder of the firing cycle being blowback
Gast a type of twin-barrel automatic gun mechanism
Gatling an early type of manually powered rotary gun; sometimes used to refer to any rotary weapon
GAU (American): Gun Aircraft Unit
Glimmspur (German): often written Gl'spur; a dimly glowing tracer for night use
GMG Grenade Machine Gun (aka AGL)

GPMG general purpose machine gun
grain measure of weight used in UK and USA for propellant charges and (in smaller calibres) projectiles. 1 gram = 15.432 grains
gravity feed the use of gravity to supply ammunition to the gun mechanism
grenade launcher a low-velocity gun designed to fire small HE projectiles
grooves the larger interior diameter of a rifled barrel; between the lands
gun gas gas generated by ignition of the propellant in a cartridge
gun pod a detachable pod, containing a gun (or guns) and ammunition, which is carried by aircraft
gyro gunsight a simple type of lead-computing gunsight to aid deflection shooting

hammer-a part of a trigger mechanism which pivots under spring pressure to strike the firing pin

hand grip or guard-the part of the rifle intended to be held by the firer's supporting (as opposed to trigger) hand

hang fire a delay in the ignition of a cartridge after the primer has been struck
Hartkernmunition (German, WW2) an APCR shot used in aircraft cannon
HC high capacity; a shell with an unusually large (HE) capacity
HE high explosive; the normal filling of cannon shells
head the rear of the cartridge, into which is fitted the primer
headspace the accurate location of a cartridge in the chamber ready for ignition
headstamp information about the cartridge, stamped into the head
HEAT high explosive, anti-tank; (see hollow charge)
heavy machine gun a machine gun with a calibre significantly larger than a military rifle cartridge but smaller than a cannon; in effect, 12.7-15 mm
HEDP high-explosive dual-purpose; a modern projectile which combines hollow-charge with general HE effect
helical drum a magazine in which all rounds point inwards, following a spiral track
high-angle mounting a mounting which permits a weapon to be elevated at or close to the vertical for AA fire
HMG heavy machine gun
hollow charge an explosive projectile with a cone-shaped hollow, lined with metal, in the nose, which generates an intense armour-piercing jet
hooded chamber a chamber which is longer than necessary to contain a cartridge; associated with API blowback designs
housing-encloses part of a gun action

HV high velocity
HVAP high velocity, armour piercing. US description for APCR, also used to describe early APDS
hybrid a mechanism which uses more than one operating principle

igniter charge intermediate charge which magnifies the primer burn, helping to burn the propellant
ignition the igniting of propellant by a primer
inert a cartridge or explosive which cannot fire or detonate
intermediate cartridge-a cartridge which is intermediate in power between the pistol rounds use in an SMG and full-power rifle/MG rounds

internal ballistics the science of the passage of a projectile down a gun barrel
iron sights-metal sights without an optical element, consisting of a rearsight close to the eye, and a foresight near the muzzle

KwK Kampfwagenkanone (German): tank gun

Lafette (German): gun mounting
lands the smaller interior diameter of a rifled barrel; between the grooves
lead computing gunsight a gunsight which calculates the correct point of aim for deflection shooting
leaf sights rearsights which consist of flat pieces of metal with a notch in the top for aiming. Several flip-up 'leaves' of different heights may be provided to allow aiming at different ranges

Leuchtspur (German): tracer; often written L'Spur
linear action a gun mechanism in which the elements reciprocate in line with the gun barrel
link an element of an ammunition belt
linkless feed a method of supplying ammunition to a gun in which the cartridges are not linked together
LMG light machine gun (can be carried by one man, usually fired from a bipod)
lock time the period of time between pressing the trigger or gun button and the first shot being fired
long recoil a type of gun operating mechanism
long-stroke piston a type of gas operation in which the gas piston is attached to the bolt carrier and drives it all the way to the back of the recoil stroke (see 'short-stroke piston')

LSW light support weapon (squad LMG)

LV low velocity

machine gun an automatic weapon of less than 20mm calibre
magazine a container which holds ammunition ready for loading into a gun
magazine follower the moving part of the magazine, between the spring and the ammunition, which transfers the spring pressure to the ammunition

manually operated a gun in which the firing cycle is operated by a manual crank or lever
MBR main battle rifle

MG machine gun (German: Maschinengewehr)
micro calibre a rifle calibre smaller than the current 5.45 / 5.56mm

Minengeschoss or M-Geschoss (German): mine shell
mine shell a thin-walled, lightweight type of HE projectile
MK (German) Maschinenkanone: automatic cannon
MMG medium machine gun: a heavy gun of rifle calibre
moteur-canon (French) motor cannon: an aircraft cannon designed for mounting between the cylinder banks of a vee-engine, firing through a hollow propeller hub.
mounting the method of supporting a gun ready for firing
multiball a cartridge which contains several projectiles (see duplex, triplex)
multipurpose ammunition ammunition with a mixture of capabilities (AP, HE, I): associated with the Norwegian firm of Nammo Raufoss
muzzle the end of the barrel from which the projectile emerges
muzzle blast the violent escape of gun gas from the muzzle as a projectile leaves the barrel
muzzle booster a device fitted to the muzzle to use some of the muzzle blast to increase recoil, to assist the action of recoil-operated guns
muzzle brake a device fitted to the muzzle which deflects part of the muzzle blast to the side or rear in order to reduce recoil
muzzle energy a calculation of the energy of a projectile as it leaves the muzzle; a function of projectile velocity and weight
muzzle velocity the speed of a projectile as it leaves the muzzle

NATO North Atlantic Treaty Organisation
neck the part of a cartridge case which holds the projectile
necked-down a cartridge case which has its neck reduced in diameter to accept a smaller calibre projectile than the case was designed for
necked-up (or necked-out) a cartridge case which has its neck increased in diameter to accept a larger calibre projectile than the case was designed for

obturation the sealing of a gun breech to prevent the escape of gun gas on firing (in automatic weapons, normally achieved by the cartridge case); also forward obturation achieved by the driving bands
obus (French): shell
OCSW Objective Crew Served Weapon; US programme for a light automatic 25mm support weapon. Now known as ACSW
OICW Objective Individual Combat Weapon; US programme for a new infantry weapon combining 5.56mm and 20mm calibres
open bolt an automatic weapon designed to commence the firing cycle without a cartridge loaded into the chamber (see closed bolt)
optical sights sights using glass lenses, which may be of unit magnification (i.e. non-magnifying) or telescopic

optronics the combination of OPtical and elecTRONIC systems to provide day/night/all-weather sights
ORO Operational Research Office (US Army)

ounce (oz) UK and USA measure of weight; 1 oz = 28.35 grams.
over-bore a cartridge which has a case capacity too large for all of the propellant to be efficiently utilised

PaK Panzerabwehrkanone (German): anti-tank gun
pan magazine a flat, circular magazine in which the cartridges are held pointing inwards: see drum and helical drum
Panzergranat patrone (German): armour piercing cartridge
Panzerbrandsprenggranatpatrone L'spur m. Zerl (German): armour piercing high-explosive incendiary cartridge with tracer and self-destruct
Patrone (German): cartridge
PDW personal defence weapon: a class of firearm midway between a pistol and a rifle, lighter and firing smaller-calibre ammunition than an SMG

penetration the ability of an AP shot to penetrate armour
percussion ignition a method of igniting cartridges by striking a percussion primer with a firing pin
PFHE pre-fragmented high explosive
Pfeilgeschoss (German) arrow shell: a long, fin-stabilised HE projectile
Picatinny rail-an American type of universal mounting rail, to which can be attached a wide range of sights and accessories

pintle mounting a type of flexible mounting in which the gun is mounted at the top of a vertical rod
pistol grip the grip for the firing hand, immediately behind the trigger

piston primer a special primer designed to be pushed out by gas pressure on firing, in order to operate the bolt unlocking mechanism

pivoting block a gun mechanism in which the breechblock movement is pivoted
pom-pom unofficial name for a slow-firing automatic weapon, usually of 37 or 40mm calibre
primary extraction the act of a gun mechanism in pulling a fired case from the chamber

primer a percussion cap fitted into the head of a cartridge case, used to ignite the propellant
primer pocket the part of a cartridge case into which the primer fits
progressive rifling rifling which commences with a gentle or zero twist, which gradually increases in twist down the length of the barrel
projectile any bullet, shot or shell fired from a gun
propellant the chemical which burns rapidly to generate gas which accelerates the projectile up the gun barrel
propeller disc the area swept by the blades of an aircraft propeller
propeller hub or boss the central part of an aircraft propeller, which may be made hollow to allow an engine-mounted gun to fire through it
proximity fuze a shell fuze which is triggered by the close proximity of a target
pyrophoric gives off sparks on impact and/or ignites spontaneously at high temperature
Pzgr Panzergranate (German): AP Projectile

R rimmed cartridge case (when it occurs at the end of a cartridge designation, as in 20x99R)
rail gun see electromagnetic gun
railway gun a gun mounted on a railway wagon
rate of fire frequency with which individual shots are fired in an automatic weapon, usually measured in rpm
rebated rim a cartridge case with a rim of smaller diameter than the case body
RB rebated rim (case description, added to the end of a cartridge designation, also given as RR)
RCAR reduced-calibre assault rifle: with a calibre smaller than the full-calibre 7.62 mm rounds

RCMG rifle calibre machine gun, typically of 7.5-8mm calibre
receiver the body of the gun, to which the barrel and operating mechanism are attached
recoil operated a gun mechanism operated by the recoiling gun barrel
reflector sight a gunsight in which the aiming marks are reflected onto an angled glass plate through which the gunner views the target
retarded blowback a variation of the blowback mechanism in which, although the bolt is never locked to the barrel, the initial movement of the bolt is resisted by a part of the action, to give the bullet time to leave the muzzle. This is sometimes referred to as delayed blowback (qv) although the principles are slightly different

reticle the markings visible in an optical sight which indicate where to aim, and sometimes the corrections needed for different ranges

revolver cannon a normally single-barrel gun with a rotating cylinder containing several chambers, each of which is loaded and unloaded in stages, and fired as it comes into line with the barrel
rifle grenade a grenade intended to be fired by a rifle; it fits onto the end of the barrel, and may either trap the bullet or permit it to pass through, using only the energy of the expanding gas to drive it (earlier models required a blank cartridge to fire them)

rifling the spiral grooving within a gun barrel which grips the projectile and spins it in order to ensure its stability (see progressive rifling)
rifling twist the angle of the rifling, normally expressed as the length of barrel required for the rifling to turn the bullet through 360 degrees

rimfire a cartridge which is ignited by means of a percussion compound contained within the rim (see centrefire)
rimless (case) a cartridge case in which the rim is the same diameter as the case body, separated from it by an extractor groove
rimmed (case) a cartridge case with a rim which has a larger diameter than the case body
rotary cannon a multi-barrel gun with several parallel barrels rotating around a common axis, each barrel being loaded and fired in turn
rotary lock the locking of the bolt to the barrel extension by a rotary movement
round (of ammunition ) a single cartridge (or equivalent)
rpg rounds per gun
RR rebated rim (also given as RB)
rpm rounds per minute; the usual measure of rate of fire
Rüstsatz, Rüstsätze field conversion set(s) (German): not fitted at the factory

sabot a sleeve into which a sub-calibre projectile is fitted, to enable it to be fired from a larger-calibre weapon: the sabot breaks up and falls away after the projectile leaves the muzzle
SABR USA: selectable assault battle rifle (alternative name for OICW)

saddle drum a type of drum magazine in which the cartridges are held in two small connected drums on either side of the action, from each of which rounds are fed in turn
salvo squeezebore a multiball system in which the projectiles are of the squeezebore type
SAP(HE) semi-armour piercing (high explosive)
SAW squad or section automatic weapon; another term for LMG

SAWS Small Arms Weapon Systems: 1960s US study

Schräge Musik jazz or oblique music (German): a type of gun mounting used by night fighters, in which the barrels point upwards and forwards
SCHV small-calibre high-velocity: US project post-1945

SCR / SCAR USA: special forces combat (assault) rifle: 2000+ project to produce modular multi-purpose rifles for special forces

SD self destruct: an HE projectile which is designed a detonate a few seconds after firing
SDR sectional density ratio; the ratio between calibre and projectile weight: together with the projectile shape this determines the ballistic coefficient
selective fire can fire semi or fully automatically
selector switch the control switch on a gun by the which the user can select between semi or fully automatic fire; it is usually combined with the safety catch and (on some models) a burst fire mode

semi-automatic a rifle which automatically fires, ejects and reloads each time the trigger is pulled: also used to describe artillery in which the fired case is automatically ejected but a new round is manually loaded
semi-rimmed (case) a cartridge case which has a rim only slightly larger in diameter than the case body, separated from it by an extractor groove: also known as semi-rimless
shaped charge see hollow charge
shell a projectile which is hollow in order to contain HE or other contents
short recoil a type of recoil-operated gun mechanism
short-stroke piston a type of gas operation in which the gas piston only moves back a short distance, 'kicking' the bolt carrier to the rear (see 'long-stroke piston')

shot any solid armour-piercing projectile (i.e. contains no HE)
shoulder the part of a cartridge case where the diameter reduces sharply from the case body to the neck
shrapnel a type of anti-personnel artillery ammunition which consists of a shell containing metal balls in the forward part and a small bursting charge at the rear, detonated by a time fuze to explode just before reaching the target: named after its 19th century inventor (nowadays loosely used to describe shell fragments)
sights the devices used to aim a gun
sight base the distance between the front and rear sights; the longer this is, the more accurately a weapon can be aimed

silencer muzzle attachment to eliminate flash and blast; more accurately known as a suppressor

single base a type of propellant
skeleton butt type of buttstock which consists of an empty frame rather than solid wood or plastic. Usually designed to fold

slant range line-of-sight range from an AA position to a target aircraft
sliding block a type of gun action locking mechanism which moves across the breech face
sling a strap used to carry, and sometimes to steady, a rifle

small arms weapons intended to be carried by a soldier rather than fitted to a mounting

SMG sub-machine gun

smoothbored a barrel which is not rifled (used with fin stabilised ammunition)
SOCOM USA: special operations command

soft recoil see counter-recoil
SOPMOD USA: special operations peculiar modifications programme

SPAAG self-propelled anti-aircraft gun: usually mounted on an AFV chassis
spin stabilised a projectile whose flight is stabilised by being rotated by rifling
SPIW USA: special purpose individual weapon (1960s project)

SPR USA: special purpose rifle (5.56 mm sniper rifle)

Sprenggranate (German): HE shell
squeeze bore a gun in which special projectiles are fired down a tapered barrel, or fitment to the end of the barrel, thereby reducing their diameter
spire point A bullet with a finely tapered nose for the optimum ballistic coefficient

SR semi-rimmed (or semi-rimless); a type of cartridge case
stabilised mounting a mounting in which the gun is kept to a constant point of aim regardless of the movement of the vehicle or ship which carries it
STANAG STANdardisation AGreement: applies to NATO equipment
Stellite a heat-resistant material used to line gun barrels
straight-cased cartridge a cartridge case which little or no taper between the head and the neck; which therefore has no shoulder

striker a long, spring-driven firing pin

striking angle the angle at which an AP projectile strikes armour plate: two different conventions have applied; in one, a strike perpendicular to the plate is called 0°, in NATO it is called 90°
strip a number of cartridges linked rigidly together for ease of loading
sub-calibre a projectile which is smaller than the bore of the gun. For firing, it is supported by a sabot. See APDS, APFSDS and full calibre
sub-calibre training a cartridge used for training purposes in a much larger calibre (usually artillery) weapon via an adaptor
sub-machine gun a portable machine gun normally designed to use pistol ammunition
sub-projectiles projectiles which are carried by a larger projectile
suppressor muzzle attachment to reduce flash and blast

SUU (American) Suspended Undercarriage Unit: used to designate aircraft gun pods

SV super velocity; implies a lighter than standard projectile
synchronised a gun mounting fitted to a piston-engined fighter in which the gun is designed to fire through the propeller disc: each shot has to be precisely timed (synchronised) to avoid hitting a propeller blade

T tracer (when attached to a projectile designation)
taboo zone restriction on the freedom of movement of a flexible gun mounting to prevent firing at own ship or aircraft
taper bore see squeeze bore
telescoped ammunition ammunition in which the projectile is buried within the cartridge case
telescoping stock-a buttstock which can be shortened to reduce its overall length

terminal ballistics the science concerning the performance of projectiles on striking the target
time fuze a fuze fitted to an HE shell which detonates it a predetermined time after firing
time of flight the time taken for a projectile to reach its target
toggle joint a type of elbow joint used in some short-recoil gun mechanisms
TP target practice: a type of projectile or cartridge used for training
tracer a chemical compound in the base of a projectile which burns slowly, giving a visible indication of its trajectory
trajectory the curve traced by a projectile in flight
traverse the movement of a gun in its mounting through a horizontal arc
triple base a type of propellant
triplex loading a cartridge which contains three projectiles (see duplex, multiball)
tripod a type of gun mounting used with light portable weapons
Trommel (German): a drum magazine
tumble when a bullet turns end-over-end, e.g. after striking the target

trunnion Projection from a gun body used to mount the gun; traditionally at the point of balance

Übungsmunition (German): often written Üb; practice ammunition

Vierling quadruple (German): a four-barrel gun mounting
VT WW2 code letters for a proximity fuze

Warsaw Pact-an Eastern European military alliance, set up in opposition to NATO and dominated by the USSR, which existed between the 1950s and the 1990s.

water-cooled a weapon which achieves barrel cooling by means of a water jacket
Wolfram (German): tungsten

yaw when a projectile fails to fly point-first, e.g. after striking something in flight; taken to extreme, the projectile tumbles end-over-end (tumbles)


Zerleger (German): self-destroying (fuze), often written Zerl; m. Zerl means mit Zerl (with self-destruct), o. Zerl means ohne Zerl (without self-destruct)


Conversion Factors

The following approximate conversion factors will convert metric to Imperial measures:

To convert millimetres to inches                  divide by 25.4

To convert centimetres to inches                divide by 2.54

To convert metres to feet                             multiply by 3.28

To convert metres to yards                          multiply by 1.1

To convert kilometres to miles                     divide by 1.61

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