German arms designer Andreas Wilhelm Schwarzlose patented a basic design for a machine gun in 1902. He subsequently sold his patent rights to the Steyr arms factory in Austria, which produced the first guns of the Schwarzlose pattern in 1905. After two years of trials and development, the military forces of the Empire adopted the Schwarzlose machine gun in 1907; this gun was also later adopted in a range of calibers by the Netherlands and Sweden (who both manufactured Schwarzlose machine guns under licence until the 1930s), and by Greece, Serbia, Romania, Bulgaria and Turkey – all before the World War I. In 1912 it was modified with the introduction of stronger parts and slightly reshaped retarding levers (struts). The primary visible difference between original M1907 guns and modified M1907/12 guns is the lack of the gap between the hump on the receiver and the barrel jacket on the latter guns.

After the WWI and the fall of the Austro-Hungarian Empire, a great many Schwarzlose guns were adopted by smaller countries that emerged from the remains of the Empire, such as Czechoslovakia (which put the gun into production) and Hungary. Many Schwarzlose guns also went to Italy as war reparations, and subsequently saw some use during WW2, mostly in Africa in the original 8×50R caliber. Another user of Schwarzlose machine guns was Russia, which captured several thousands of Austrian machine guns during the early parts of World War One.
The Schwarzlose machine gun, although overshadowed by more famous weapons such as the Maxim or Browning, has its own merits. It is quite simple in construction, robust in service, and usually quite reliable. Its drawbacks come from its basic design, which centers on a retarded-blowback action. This action calls for a relatively short barrel so that the chamber pressure drops before the case begins to leave the chamber; otherwise it would rupture – although when the Czechoslovak army converted their old 8×50R Schwarzlose machine guns to the more powerful 7.92×57 Mauser ammunition, they had no problems associated with high pressure, even with new, significantly longer barrels. Nevertheless, most of the Schwarzlose guns retained short barrels throughout their service life. This obviously limited the muzzle velocity and thus the maximum range and possible bullet penetration at any given range, compared with contemporary guns with a locked breech. The short barrel also called for a dedicated flash hider, to suppress the significant muzzle flash which otherwise would blind the gunner at night. Finally, the lack of primary extraction required an integral oiler, which squirted a small amount of oil into the chamber just before chambering the next round. Nevertheless, the Schwarzlose was a good weapon and saw considerable use through both world wars, although during the Second World War it was mostly relegated to second-line troops, fortifications and other such uses.

The Schwarzlose machine gun is a retarded-blowback operated, water cooled, belt-fed weapon that fires from a closed bolt. The method of operation requires a heavy breechblock, connected to the receiver through a pair of knee-joint struts. When the bolt is in battery, the struts are folded forward, with their joint axis lying relatively low above the barrel axis. Upon firing, the pressure of the powder gases acts on the breechblock through the base of the cartridge case. The rearward movement of the breechblock unfolds the struts, but because of a carefully arranged redirection of forces through the struts and joints, most of the initial pressure is transferred to the receiver. Upon further recoil, joint axis rises above the barrel, and thus the recoil force is re-distributed with more and more of it being used for bolt acceleration. Upon recoil, the bolt compresses a massive and powerful return spring which forces it forward and into battery once the recoil stroke is completed. The charging handle is attached to the axis of the forward strut, and has to be rotated back to cycle the bolt.
Due to the lack of primary extraction, the Schwarzlose has to use oiled cartridges. To avoid the problems associated with factory-oiled or waxed ammunition (which tends to collect fine dust and then cause jams) the gun has an internal oiling system which squirts a small amount of oil into the chamber just before the chambering of each round. This system includes an oil reservoir, located in the receiver’s top cover, and a small oil pump, which is operated by the reciprocating bolt.
The belt feed system is very simple, and involves few parts. The major part is the star-wheel, located in the lower left corner of receiver. Upon bolt recoil, the star-wheel is rotated for one step by the interaction of the cam surfaces on the bolt and the wheel. Each cartridge has to make three steps in the feed before being presented to the bolt for chambering, therefore initial belt loading requires three deliberate pulls on the charging handle. The feed direction is from the right side only, ejection being to the left.
The trigger system also is of rather simply design. It involves a separate striker, a striker spring and a sear, mounted on the bolt. The sear is cocked by a lever attached to the rear bolt delaying strut, and this cocking movement adds to the retarding force applied to the bolt. After cocking the striker is held to the rear by the sear. The thumb trigger is located at the rear of the receiver, and once pushed by the operator, it holds the connection bar so it trips the sear when the bolt is in battery. A manual safety is located next to the trigger and blocks it unless pushed forward by the operator’s left thumb. Dual spade grips are located horizontally at either side of the receiver, and can be folded up for storage or transportation.
The most common mounting was a tripod of solid construction, with tubular legs of adjustable height and traverse and elevation mechanisms. An optional armored shield was available for this gun, which was unusual in that it also provided frontal and lateral armored protection for the thin metal of the water jacket. Alternatively, a low-height, lightweight tripod was provided for the “light” role. This tripod had no traverse and elevation mechanisms.

Schwarzlose M1907 machine gun on Dutch-made M\25 tripod, with AA sight

Schwarzlose M1907/12 machine gun on standard Austrian tripod; spade grips are folded up

Schwarzlose M1907/12 machine gun on standard Austrian tripod; spade grips are in ready position, and a shoulder stock is attached

Schwarzlose M1907/24 (Vz.24) machine gun, interwar Czechoslovak conversion to 7.92×57 mauser caliber; note that it has longer barrel and jacket

]]> http://fire-arms.info/archives/schwarzlose-m1907-and-m190712/feed 0 http://fire-arms.info/archives/chauchat-csrg-model-1915-light http://fire-arms.info/archives/chauchat-csrg-model-1915-light#comments Wed, 26 Aug 2009 15:39:44 +0000 Megan http://fire-arms.info/?p=170

French army showed some advanced thinking in terms of small arms prior to and during World War One. For example, the French were among the first to adopt and mass-issue semi-automatic rifles. They also were among the first manufacturers of inexpensive, production-oriented squad automatic weapons, namely the infamous CSRG M1915, otherwise known as the Chauchat after the person who led the development commission (CSRG stands for Chauchat, Suterre, Ribeyrolle and Gladiator – the first three being the names of the designers and the last one being the name of the manufacturer, French bicycle-making company Établissements des Cycles “Clément-Gladiator”).
The entire gun was developed so its parts can be made in almost every mechanical workshop with generic lathe equipment, and with loose tolerances. This weapon was one of the lightest in its class, being about 2-3 kilograms lighter than the Lewis LMG; but it also was the least reliable, in part because of its complicated design and in part because of the crude machining and loose fitting of its operating parts, resulting in a wide variety of jams and stoppages. It was also prone to self-disassembly under prolonged firing, if parts became worn. Other sources of trouble were an open-side magazine which easily collected dirt and dust, and an outdated cartridge with a severe taper of the case combined with a large diameter rim.
In fact, the Chauchat light machine gun is often considered as the worst weapon of its class, ever produced in quantity. Nevertheless, the CSRG was produced in great numbers in spite of availability of better (and of course more expensive) weapons, such as the Hotchkiss Portative, Lewis or Madsen, and issued not only to French troops, but also to the American Expeditionary corps in Europe, first in the original French 8×50R chambering, and then in the .30-06 US chambering. Alongside the criticisms there are more favourable reports of its successful use and it is probably fair to say that, despite its problems, it was still better than nothing. Some sources claim that as many as 250,000 8mm M1915 plus almost 40,000.30-06 M1918 were built during the Great War. Several countries (such as Belgium, Greece and Poland) even used this weapon during the early 1920s, adapted to their domestic military ammunition.

The Chauchat light machine gun is long recoil operated, selective-fire weapon which fires from an open bolt. The barrel has an aluminum radiator with radial fins, and is enclosed by a tubular jacket with cooling holes and a conical flash hider at the front. The front of the barrel jacket serves as a muzzle recoil booster, using the pressure of the powder gases acting on the muzzle to increase the recoil force.
The barrel is screwed into the front of the long tubular barrel extension. This extension is bored internally to provide a channel for the bolt with a rotating head which has two locking lugs at the front. Bolt head rotation is controlled by cam tracks cut in the bolt body, which interact with projections made on the tail of the bolt head. There are two separate return springs, co-axially located in the tubular receiver – bolt spring and barrel spring. The receiver is of tubular shape, with long box-like trigger / magazine housing attached below.
When the gun is cocked, the bolt is held back by the sear, and the barrel is in the forward position. When the trigger is pressed, the sear releases the bolt, which goes forward, stripping the first cartridge from the magazine and forcing it into the chamber. Once the bolt head comes into battery, the forward movement of the bolt body forces it to rotate and lock the bolt to the barrel. At the end of the bolt movement the firing pin strikes the primer of the loaded cartridge and discharges the gun. The recoil of the discharge the moves the barrel group (barrel and its extension) along with the bolt group to the rear. At the end of the recoil movement the bolt is held by the sear, but the barrel is free to return forwards under the pressure of its own spring. This movement causes the bolt head to move relative to the now stationary bolt body, which in turn causes the bolt head to rotate and unlock from the barrel. The barrel then goes forward, leaving the fired case on the face of the bolt head. As soon as the fired cartridge case is clear from the barrel, it is ejected through the aperture on the right side of the gun by a spring-loaded plunger type ejector. If the gun is set to automatic fire and the trigger is still held back when barrel goes fully forward, it releases the bolt from the sear, so it can load and fire the next round.
The feed system uses single-stack box magazines of semi-circular shape, necessary because of the severely tapered and rimmed cases of the French service rifle cartridge. The magazine has large openings in the right wall, probably designed to lighten it and allow an easy visual check of remaining ammunition.
The trigger system is over-complicated as it requires a special link to release the sear in automatic fire once the barrel is in battery. The combined safety / fire mode selector lever is located on the left side of the trigger housing, above the pistol grip.
Basic furniture includes a wooden butt, a separate pistol grip, and a vertical foregrip located between the trigger guard and the magazine. A lightweight folding bipod is attached to the front of the trigger / magazine housing, below the barrel jacket.
Modifications:
Chauchat machine rifle, M1918: a modification of basic M1915 design, produced in France for the US Expeditionary Corps in Europe. This version was adapted for the US 7.62×63 (.30-06) rimless ammunition, and used extended magazine housing and slightly curved box magazines that held only 16 rounds. This was even less reliable than original 8mm version, because of the different ballistic properties of the American cartridge and manufacturing problems when producing .30-06 barrels with out-of-spec chambers.

Chauchat C.S.R.G. Model 1915 light machine gun, caliber 8×50R, with bipod unfolded

Chauchat C.S.R.G. Model 1915 light machine gun, with bipod folded

Chauchat C.S.R.G. Model 1918 light machine gun, caliber .30-06 US.

Type 67 was the first Chinese general purpose machine gun, developed to replace earlier Type 53 and Type 57 7,62mm medium machine guns (license-built copies of Soviet SG-43 and SGM respectively). This weapon combined features borrowed from many other machine guns, and went through a number of variations, still serving with PLA (Chinese People’s Liberation Army). Development of a new medium machine gun commenced in 1959, with first prototypes tested in 1963. At that time the concept of a new weapon was broaden from medium to universal machine gun. Adopted in 1967, it was improved with the introduction of the Type 67-1 in 1978. In 1982 PLA has adopted the Type 67-2 GPMG, which was somewhat lighter and used a lighter tripod. Type 67-2 is so far a standard general purpose machine gun of PLA. It saw limited use during closing days of Vietnam war, and few guns of this type also found its way (through the Pakistan) into the hands of Afghanistan mujaheds that fought Soviet army during early 1980s.

Type 67 machine gun is gas operated, air cooled, belt fed machine gun that fires from open bolt. Barrel is quick-detachable. It uses ZB-26 type vertically tilting bolt to lock the barrel. Feed is from right side only, using steel, non-disintegrating belts with open pockets (type 67-2 belts are assembled from 25-round pieces using cartridge as an inter-link). To avoid two-stage feed with rimmed ammunition, Type 67 uses push-out type feed, where cartridges are pushed down and out of the link by the cams in the feed module, then fed forward and into the chamber by the closing bolt. Standard belt capacity is 250 rounds, but for LMG role 100-round belts can be loaded into drum-type container which can be clipped to the receiver. Belt is said to be incompatible with any other weapon. Early Type 67 machine guns had fluted barrels; Type 67-1 and 67-2 have smooth barrels, probably as a cost-saving measure, type 67-2 barrels also are somewhat lighter than earlier ones. Furniture (pistol grip and shoulder stock) was made from wood on Type 67 and from polymer on later Type 67-1 and 67-2 weapons. Every Type 67 machine gun is fitted with integral, folding bipod, and also can be installed on infantry tripod. Type 67 and Type 67-1 tripods had legs made from heavy steel tubes; Type 67-2 tripod had lighter legs made from steel stampings.

Type 67 machine gun on tripod, with 100-round drum belt container attached to the right side of receiver

Type 67-2 general purpose machine gun on tripod; note that tripod is different from original type 67

Type 67-2 general purpose machine gun in light machine gun role, on integral bipod

Caliber: 7.62×54mmR
Weight: 11 kg (gun) + 13 kg (tripod, Type 67) or 5 kg (tripod, Type 67-2)
Length: 1345 mm
Length of barrel: 605 mm
Feeding: belt, 100 or 250 rounds
Rate of fire: 650-700 rounds/min

The Minimi light machine gun was developed by the famous Belgian company FN Herstal, in the late 1970s and early 1980s. Mass production began in 1982 in Belgium, and at about the same time it has been adopted by the US Armed forces as the M249 Squad Automatic Weapon (SAW). Since its introduction Minimi has seen widespread service, and numerous variations have been developed. First, the Para (Paratroop) version came out, with shorter barrel and tubular telescoped butt. This gun traded off some of the range and firepower for compactness and maneuverability. Quite recently, an SPW version was developed, which featured a Para-type buttstock, a barrel of intermediate length (between standard and Para models), and a Picatinny-type rail mount, which allows a wide variety of sights and scopes to be mounted. To save weight, the magazine feed option of the standard and para models has been discarded. This version, in a slightly modified form, was adopted by the US Special Forces Command (US SOCOM) as the Mk.46 model 0 light machine gun.

The FN Minimi has an excellent reputation on reliability and firepower, and the latest reports on failures of M249 SAW weapons in Iraq are attributed to the age of the weapons used – most of the current issue M249 in US Army are more than 10 years old and quite worn out.
Technical description.
The FN Minimi / M249 SAW is an air cooled, gas operated, belt fed, automatic weapon. The Minimi is operated using conventional gas action with the gas piston located below the barrel, and the barrel is locked using the traditional rotary bolt. The barrel is quick-detachable, and has a carrying handle attached to it, to help for quick replacement procedure. The M249 has an alternative feed system, which allows to use disintegrating metallic belts as a primary feed option, or M16-type box magazines as a back-up feed option. The belt is feed using the top feed unit, the magazines are inserted through the magazine port, located at the left side of the receiver and angled down. The Flip-up dust cover closes the magazine port when it is not in use, serving also as a belt guide. When magazine is in place, this cover raises up and closes the belt-way to avoid dual feeds and jams. Since the belt feed uses additional power to pull the belt through the gun, the rate of fire with the belt is somewhat slower (~ 750 rpm) than the rate of fire with magazine feed (~ 1000 rpm). The latest SPW and Mk.46 mod.0 versions of the Minimi have no magazine feed module as a weight-saving measure. The belts are fed from special 200 rounds plastic boxes that can be clipped beneath the receiver. All Minimi versions fire from open bolt to ensure optimal barrel cooling between bursts.

The folding bipod is mounded under the gas chamber, and the gun has provisions for tripod or vehicle mountings. The open sights are standard, with the availability of vide variety of optical and night sights for SPW and Mk.46 versions with Picatinny rails.

FN Minimi – Belgian-made version of basic machine gun. Note the lack of the heat shield above the barrel, and the tubular buttstock.

FN M249 SAW

FN Minimi Para – a short-barreled “paratrooper” version with telescoped buttstock in extended position

FN Minimi SPW – Special Purpose Weapon, a lightened version with Picatinny rail adapters, Para type buttstock (shown folded) and belt feed only (no magazine feed installed)


FN Mk.46 model 0 – a variation of the Minimi SPW, with additional Picatinny rail on the heat shield and the different butt, developed for US Special Forces.

The history of Danish Machine guns is closely tied to one company and one name, although there were, in fact, far more names behind the whole story. The company in question was originally known as Dansk Rekyl Riffel Syndikat A/S, and the name that became a symbol of a Danish military industry was the Madsen. Vilhelm Herman Oluf Madsen was the War Minister of Denmark who, among other things, supported the development of domestic automatic arms. This development commenced circa 1890, when Jens Theodor Schouboe, a lieutenant in the Danish army, started development of a semi-automatic rifle. When this rifle was adopted by the Danish Marines in 1896, a new company was founded to produce this rifle and its derivatives for domestic use and export, and it was the aforementioned Dansk Rekyl Riffel Syndikat. Further development of the rifle continued under the leadership of Schouboe and the factory director Rasmussen, and by the 1902 the top-loading semiautomatic rifle evolved into a magazine-fed machine rifle, which in fact became the world’s first mass-produced light machine gun.
In a relatively short time Madsen machine rifles found their way into a number of European countries, being adopted or purchased in significant numbers by Austro-Hungary, France, Great Britain, Russia, Sweden, and a number of other powers. During the Great War, license manufacture was planned to be established in Russia and UK, although this did not happen in either country – in Russia because of the turmoil of the revolution of 1917 and in the UK because of financial disagreements. Nevertheless, large numbers of Madsen light machine guns (so named after the greatest promoter of the gun) were built and exported from Denmark from about 1905 and until about 1950, when mass production of this remarkable weapon ceased. It must be noted, however, that the Madsen LMG was offered through company catalogues up until mid-1960s, apparently on “made on order” basis, in ‘any military rifle caliber between 6.5 an 8 mm’, including then-new 7.62×51 NATO.Through the first half of the twentieth century several dozens of countries purchased Madsen light machine guns; those included Finland, Great Britain, Netherlands, China, Imperial Russia, Portugal, and a number of other South American and Asian countries. Of course, Denmark itself also made a good use of Madsen guns. Most users discarded their “obsolete” Madsen guns by the 1970s, although some guns were and still are used in more remote parts of the world. In Indonesia, Madsen guns were used for training until about 1980, and very recently a few Madsen guns were observed in the hands of Mexican police forces, providing fire support against heavily armed gangs during anti-drug raids.

The Madsen light machine gun is a recoil-operated, magazine-fed, air-cooled weapon that fires from a closed bolt. It uses one of most unusual operating systems with a non-ramming breechblock, broadly derived from the 19th century single-shot Peabody-Martini rifles. Despite its apparent complication, the Madsen was usually of high production quality, and worked reasonably well, especially in non-rimmed cartridges. Over fifty years of production, these machine guns were manufactured in about a dozen calibres from 6.5mm to 8mm, and in a great number of variations which differed in the shape of the accessories, minor parts details etc.
The barrel of the gun is heavily finned and enclosed within a tubular jacket with a number of cooling ports. On late production guns the front of the barrel jacket also serves as a recoil booster and a flash hider. If necessary, the hot barrel can be replaced with a fresh one under field condition in reasonable time.
The basic action can be described as short-recoil operated, with a non-reciprocating, swinging breechblock. The recoiling barrel is attached to the barrel extension, which in turn holds a breechblock that is permitted to swing up and down relative to the axis of the breech. The swinging axis is located toward the rear end of the breechblock. When the breechblock is lowered below the bore axis, loading is achieved through the use of a separate swinging arm; when the breechblock is raised above the bore axis, extraction and ejection can take place. Therefore, the entire feed / lock / ejection cycle is controlled by three separate sub-assemblies – feed arm, breechblock, and extractor / ejector. Movement of all those parts is independently but synchronously controlled by cams in the stationary receiver of the gun.
Starting with the gun unloaded and the barrel locked by the breech block, the loading and firing sequence is as follows: when the charging handle is pulled, the barrel group is pulled rearwards; this causes a stud on the breechblock to follow a cam path cut in the right receiver sideplate. During this rearward movement, the breechblock is first raised up, and on the end of the stroke then dropped down, and the breech is exposed for loading. Upon completion of the rearward cycle, the cocking handle is released and the barrel group goes forward under the power of the return spring. The breech block initially remains lowered, while its controlling stud follows the lower part of the cam track; at the same time, first a special feed rammer pushes the bottom cartridge from the magazine to the right, and into the channel cut in the upper part of the breechblock; then, a fork-shaped bottom extension of the feed arm strikes the projection in receiver, so the upper part of the arm is sent forward with greater speed, feeding the cartridge on the breechblock forward and into the chamber. As soon as the cartridge is chambered, the breech block rises to a position in line with the barrel, is locked rigidly and the gun is then ready to shoot. When the operator pulls the trigger, it releases the hammer which, via a linkage, strikes the firing pin and discharges the gun. Recoil forces the barrel back against the return spring. Upon recoil, the stud on the breechblock follows the upper part of the cam track and first lifts the breechblock above the bore axis. As soon as breechblock is raised, a separate extractor / ejector propels the cartridge case from the chamber and out of the gun, through the aperture at the bottom of the receiver. At the end of the recoil stroke, the stud on the bolt follows the descending part of the cam track, lowering the breechblock below the bore axis and preparing the gun for the loading of the next round. The loading cycle continues as described above, and if the trigger is still held back and the mode selector is set to automatic fire, the gun will fire automatically as soon as the counter-recoil / loading cycle is complete.
The ammunition feed is from top-mounted curved box magazines; early guns had single stack magazines better adapted to rimmed ammunition, while some late-production guns were provided with double-stack, single-position feed magazines. Madsen magazines are somewhat unusual as their feed position is offset to the side of the magazine, because the magazine is offset to the left of the gun axis. This is necessary for the oscillating feed arm, which is located to the left of the breechblock, to be able to pick up fresh cartridges and send them up to the chamber above the dropped breechblock. Depending on the version and caliber, the magazine capacity usually varied between 25 and 40 rounds, although 30-round magazines were probably the most common.
Ejection is to the bottom, through an aperture in front of the trigger guard. This aperture is fitted with a dust cover which is opened before firing by swinging it down and rearwards.
The firing system consists of a conventional trigger which operates an internal hammer, and a manual safety / fire selector switch, located on the left side of receiver, above and in front of the trigger guard.
Standard furniture includes a wooden butt and a folding bipod, attached to the barrel jacket. A variety of folding carrying handles was provided on some versions of the gun. Additional accessories also included rear monopod, which was installed under the butt, and a variety of infantry and AA tripods and mountings. Unlike most MGs with top-mounted magazines, the Madsen does not require offset sights as the magazine is offset, away from the sight line.

Danish M/1896 selfloading rifle designed by Jens Shouboe and used by Danish marine infantry; this weapon served as a starting point for a whole line of Madsen light machine guns

Madsen model 1902 light machine gun, Denmark

Madsen model 1903-21 light machine gun, Denmark

Madsen model 1929 aircraft observer machine gun, Denmark

Madsen model 1940 machine gun, as used in Portugal

Short-barreled Madsen light machine gun, as used in 1930s and 1940s in Dutch West India colonies.

Madsen model 1948 light machine gun, Denmark

Madsen model 1950 light machine gun on universal tripod in AA configuration, from Madsen catalogue

Diagram explaining the action of the Madsen light machine gun

Data for Madsen model 1950 LMG:

During the late 1920s Waffenfabrik Solothurn, a Swiss private business that emerged in the watch-making industry but later turned to the production of small-arms parts, was bought by the German concern Rheinmetall, to serve as a research and development facility away from the watchful eyes of the Allied Control Commission, established in 1918 as a result of Treaties of Versailles. In 1929 Waffenfabrik Solothurn brought out its first practical machine gun, known by the factory as the S2-100, and in export catalogs as the MG 29. Next year Solothurn announced an updated version, the S2-200, also known as the MG 30. It was, in essence, a typical light machine gun – recoil operated and magazine fed, although Solothurn also offered a complicated universal tripod for this gun. The Solothurn MG30 earned its place in history by being adopted by Austria in 1930 and Hungary in 1931 (in both cases chambered for 8×56R ammunition), and it also served as the starting point for several German machine guns, such as the MG 15 (aircraft) and MG 34. It is also must be noted that most of components of the MG30 were produced in Austria at the Steyr factory; Solothurn carried out the final assembly and test-firing.The Solothurn S2-200 machine gun is a short-recoil operated, air cooled, magazine-fed weapon. It uses a locking ring, which is located at the end of the barrel extension, to lock the bolt. Inside the locking ring, there are six sets of locking lugs, arranged as an interrupted thread. These lugs are mated with lugs cut at the rear of the bolt. Rotation of the ring, which locks and unlocks the bolt, is controlled by rollers mounted on the outside of the ring. Upon recoil, these rollers follow cam tracks cut into the receiver. The gun is of relatively simple design, with most parts having a round cross-section. The tubular receiver is an extension of the barrel jacket. The butt hosts a tube which contains the return spring and its guide. During disassembly, the butt is unlocked and rotated to disengage it from the receiver, then removed. This permits the entire barrel / bolt group to be pulled or shaken off the receiver for replacement. Since the bolt is held attached to the barrel extension, it needs to be removed from the hot barrel and attached to the cold one before reassembly; this procedure requires a heat-insulated glove to handle the hot barrel.
The trigger is of the rocking type and allows for single shots and automatic fire. The selection of fire mode is made by pressing either the top (single shots) or bottom (automatic) part of the trigger. Ammunition feed is from curved box magazines, inserted from the left side; ejection is to the right.
The gun is normally fitted with a folding bipod, although Solothurn also produced a sophisticated universal tripod, with a remote trigger and a traverse and elevation mechanism, and recoil buffers.
Modifications:
S2-100 / MG 29: a direct predecessor to the S2-200, made in very limited numbers in 1929-30. Key difference from S2-200 is that buttstock cannot be removed so quickly.
MG 30 (Austria): same as S2-200 except for ammunition used – it was chambered for 8×56R rimmed ammunition, which required magazines of more curved shape
31M (Hungary): same as MG 30

Steyr-Solothurn S2-100 light machine gun

Steyr-Solothurn S2-200 / MG 30 light machine gun, Austria

Steyr-Solothurn S2-200 / 31M light machine gun, Hungary

Caliber	7.92×57, 8×56R
Weight	9.5 kg
Length	1162 mm
Barrel length	600 mm
Feed	Magazine, 30 rounds
Rate of fire	550 rounds per minute

]]> http://fire-arms.info/archives/steyr-solothurn-s2-100-s2-200-mg-30-31m-machine-gun/feed 0 http://fire-arms.info/archives/browning-m1921-m2-m2hb-m2b-qcb-heavy-machine-gun http://fire-arms.info/archives/browning-m1921-m2-m2hb-m2b-qcb-heavy-machine-gun#comments Tue, 21 Jul 2009 21:32:29 +0000 Megan http://fire-arms.info/?p=53

The development of a large-caliber heavy machine gun in USA was initiated in 1918, at the direct request of General Pershing, the commander of the US expeditionary corps in Europe. He requested a heavy gun capable of destroying military aircraft and ground targets such as tanks and armored cars. The task of developing such a gun and ammunition was passed to John Browning (then based at Colt’s factory) and the Winchester Arms Co. respectively. The basic pattern of the new heavy machine gun was sealed in 1921. Officially adopted in 1923 as “machine gun, .50 calibre, M1921”, this water cooled, belt fed gun became the prime AA weapon for the infantry and the navy.
In the year 1930 US Army adopted a slightly modified .50 caliber M1921A1 machine gun, and further work on this gun concentrated on the development of a universal weapon suitable for most roles. The key design changes were made by Dr. Samuel G. Green, who redesigned the basic receiver so it could be used in conjunction with either water-cooled or air-cooled barrels, encased in a water jacket or short perforated sleeve respectively. He also developed a switchable left or right side belt-feeding unit. The US Army adopted the new, improved fifty-caliber machine gun as the M2, in a water-cooled anti-aircraft version, an air-cooled ground mount version and as an aircraft weapon. Since the original air-cooled barrels were too light to provide any degree of sustained fire in ground applications, heavier barrels were soon introduced for the ground-mounted guns, so this weapon became the “M2 Heavy Barrel” or M2HB for short. In 1938 the barrel of the M2HB was lengthened to provide more striking energy and longer range, and in this form the M2HB was made in great numbers during the Second World War.US arms factories turned out a little less than 2 million M2 guns in all versions between 1941 and 1945, of which over 400,000 were made in M2HB configuration for ground use.
After the WW2, .50-caliber Browning guns found a wide acceptance across the world, and today are still widely used as ground and vehicle guns in most of NATO countries and many others. Production of new M2HB guns is continued in USA and Belgium.Browning M2HB machine gun is belt-fed, air-cooled machine weapon capable of semi-automatic and automatic fire. The M2HB fires from a closed bolt at all times, and uses a short-recoil operated action with a vertically sliding locking block, which rises up to lock the bolt to the barrel extension, and drops down on recoil to unlock the bolt from the barrel. It also has a bolt accelerator, made in the form of  a lever located at the bottom of the receiver. Upon recoil, once the barrel is unlocked from the bolt, it strikes the accelerator, so the kinetic energy of the recoiling barrel is quickly transmitted to the bolt, improving the reliability of the weapon. Barrels are screwed into the barrel extension and are not quick-detachable on standard M2HB weapons; furthermore, once the barrel is installed in the weapon, the headspace must be adjusted prior to firing, or the weapon may fail to fire or produce a serious jam. However, quick change barrel (QCB) kits were developed by several companies during the 1970s and 1980s, and every M2HB weapon can be converted to a QCB version with the replacement of only a few parts, including the barrel. The rear part of the barrel is enclosed in a short, tubular, barrel jacket with cooling slots. The back of the receiver houses a bolt buffer, and additional buffer is used to soften the movement of the heavy barrel. On infantry guns, the cocking handle was invariably installed on the right side of the weapon, but slots were made on both sides of the receiver for tank installations which may require a left-side cocking handle.
Browning M2HB machine guns use a disintegrating steel belt, with the feed switchable from one side to the other through the re-installation of certain parts in the feed unit. The belt feed is of the two stage type – every cartridge is first withdrawn from the belt toward the rear by the pivoting extractor lever, attached to the bolt. Once the cartridge is clear of the belt, it is lowered into a T-slot cut into the bolt face, and pushed forward into the barrel. Spent cartridge cases are forced down the T-slot and out of the weapon through an opening at the bottom of the receiver by the following cartridges, or by the pivoting belt extractor lever (for the last cartridge case). A rotary switch is used to select the track for left or right side feed.
Since the gun fires from a closed bolt, it has a separate firing pin, powered by its own spring, and hosted inside the bolt along with the sear and cocking lever. Upon the recoil stroke of the bolt, the cocking lever pulls the firing pin back until it is engaged by the sear. Once the bolt is fully in battery (locked closed), a pull on the trigger raises the trigger bar so it acts on the sear and releases the firing pin. The standard firing controls consist of a push-type thumb trigger and sear release buttons located between the dual spade grips. Alternatively, an electric solenoid trigger can be installed for mounted vehicle applications. The M2HB has an unusual method of providing semi-automatic fire (probably added to the basic design as an afterthought) – it has a bolt latch, which locks the bolt to the bolt buffer in the open position after each shot. Therefore, if gun is fired in semi-automatic mode (single shots), for each shot the operator must first release the bolt forward by pressing the bolt latch release, located next to the thumb trigger (as the gun fires from a closed bolt). After the bolt is released and the gun is loaded, the operator may push the trigger to fire a single bullet. If the automatic mode is desired, the bolt latch must be turned off and locked by turning its lock to the left. In this position it will not engage the bolt and the gun will fire continuously as long as the trigger is pressed. It must be noted that original M2HB guns had no manual safeties; however, the recent M2E2 upgrade, developed by General Dynamics, includes, among other items, an additional manual safety located next to the trigger.
Standard sights consist of a folding blade front and frame-type rear. The rear sight is mounted on the receiver, the front sight is located at the front of the receiver and protected by an arc-shaped sight protector. Additionally, various types of telescopic and night sights can be installed using appropriate mountings.

John Browning testing his prototype .50 caliber heavy machine gun, circa 1919

Twin AA mount with Browning M2 water-cooled machine guns in action

Browning M2HB air-cooled machine gun on M3 tripod

Browning M2HB-QCB air-cooled machine gun of current manufacture with quick-change barrel, on M3 tripod

Caliber: .50BMG (12,7×99mm)
Weight: 38 kg MG, 58 kg complete with M3 tripod
Length: 1650 mm
Length of barrel: 1140 mm
Feeding: belt
Rate of fire: 450-600 rounds/min

In around 1921 the Czechoslovak army also started a quest for a light machine gun. Early trials included foreign designs such as Berthier, Browning BAR M1918, Darne, Hotchkiss, Madsen and St.Etienne, and several domestic designs. Of those, the most important was the Praha II LMG, a lightweight, belt fed weapon built at Česka Zbrojovka (CZ) Praha (Czech Arms factory in Prague) and designed by brothers Vaclav and Emmanuel Holek. In the following year the Holek brothers abandoned the belt feed in favour of a top-feeding box magazine, and the resulting weapon, known as the Praha I-23, was selected. Since CZ-Praha was a relatively small factory with limited industrial capabilities, it was decided to transfer the production of the new light machine gun to a more advanced arms factory in the city of Brno, known as Zbrojovka Brno, or ZB in short. This transfer resulted in a long series of court trials over royalties, between the owners of the design (CZ-Praha) and the manufacturer (ZB).
Despite the legal troubles, manufacture of the new weapon had commenced at the ZB factory by late 1926, and it became the standard light machine gun of the Czechoslovak army by 1928. Universally known under its factory designation ZB26 (the military designation in the Czechoslovak army was lehky kulomet Vzor 26, or LK Vz.26 in short), this LMG became one of the most successful infantry small arms of the interwar period. It is believed that the ZB factory turned more than 120,000 ZB-26 guns between 1926 and 1939 in a variety of calibers (the most popular being its original 7.92×57 Mauser). It was exported to twenty-four European, South American and Asian countries, both in its original form and in the slightly improved ZB30 version. Large batches of ZB light machine guns went to Bolivia, Bulgaria, China, Rumania, Turkey and Yugoslavia. Exports continued up until 1939, when Hitler’s Germany took over Czechoslovakia. The Germans quickly recognized and adopted a good weapon when they saw it, and the ZB26 immediately became the MG 26(t) in German service. The Waffenwerke Brunn (the German name for ZB during the occupation) kept turning out the ZB26 LMG in significant numbers, and these machine guns were issued to Waffen-SS and various occupation forces. It must also be noted that the ZB26, in its improved ZGB33 version, eventually became the Bren, an extremely successful light machine gun widely used throughout the British Commonwealth between the late 1930s and the 1980s.

The ZB26 is a gas operated, air cooled, selectively fired, machine gun. It has a finned, quick-detachable barrel and fires from an open bolt. The action of the gun is powered by a long-stroke gas piston, located below the barrel. The gas block is mounted at the muzzle end of the barrel and also serves as the front sight base. The action is locked by tipping the rear of the bolt (breechblock) upwards, and into a locking recess in the receiver. The return spring is located in the butt of the weapon, and is connected to the bolt carrier / gas piston via a long rod; additionally, there is a short spring buffer located around the return spring at the juncture of the receiver and butt, which softens the impact of the bolt group at the end of its rearward stroke. The charging handle is located at the right side of receiver and does not reciprocate when the gun is fired.
The ammunition feed is from top-mounted box magazines. These are made from sheet steel and hold only 20 rounds in a two-row configuration. The magazine housing has a sliding dust cover which is slid forward to load the gun. Spent cartridges are ejected downwards. The ejection port is normally closed with its own dust cover which opens automatically once the trigger is pressed. The trigger unit permits both single shots and automatic fire, selectable through a safety / fire mode selector lever situated at the left side of the pistol grip. The gun fires from an open bolt and the spring-loaded firing pin is operated by a projection on the bolt carrier, once the bolt is fully in battery and locked.
Because of the overhead magazine, the sight line is offset to the left, and the front sight is mounted on a base which protrudes upward and to the left from the gas block. The rear sight is attached to the left side of receiver, and has a range adjustment mechanism controlled by a knurled rotating knob. Standard furniture consists of an integral folding bipod, which is attached to the gas cylinder tube, and a wooden butt with a spring-buffered buttplate and a folding shoulder rest plate. Despite the fact that the ZB26 was intended for the light machine gun role, it was also offered with a sustained-fire tripod, and provided with a sufficient supply of full magazines and spare barrels it could serve (to some extent) as a medium machine gun. The same tripod was also adaptable for the AA role.

Modifications.
ZB30: an improved version of the basic design, which appeared in 1930. Basic improvements included the addition of a gas regulator to the gas block and a barrel of somewhat different shape, with a changed interface with the receiver (so the barrel cannot be installed improperly). Other changes include different markings on the safety / fire mode selector. The ZB30 was manufactured under licence in Rumania, Yugoslavia and Nationalist China.
ZGB33: a modified ZB30 adapted to use rimmed British ammunition (.303 British / 7.7×57R). Basically, a prototype for the British Bren machine gun

Experimental Praha I-23 light machine gun, developed by Holek brothers at Prague arms factory in 1923

ZB vz.26 light machine gun, right side

ZB vz.26 light machine gun, left side

ZB 30 machine gun

Caliber: 7.92×57 mm Mauser
Weight: 8,9 kg
Length: 1168 mm
Length of barrel: 600 mm
Feeding: box magazine, 20 rounds
Rate of fire: 500 rounds/min