Monday, July 4, 2011

Old concepts, new designs

Originating from the MG42, the German MG3 machine gun can truly be called an old soldier in the world of small arms design. The Russian RPK-74 is in concept a 7.62mm RPK scaled down to 5.45mm ammunition. The American M60, however, was a machine gun that caused considerable problems and was therefore very unpopular with its users.

The Maschinengewehr MG3
The MG3 is a modified version of the German MG42 belt-fed, air-cooled machine gun adapted to fire 7.62mm NATO Ml3 or DM 6 disintegrating link or German DM 1 continuous link. (When continuous link has been fired, the empty belt hangs off the gun for reloading later; disintegrating link unclips itself as it is fired.) It is in service in many countries including Chile, Denmark, Saudi Arabia, Norway, Austria and Portugal. The Sarac, an MG3 copy, is built in the former Yugoslavia, and the MG3 is made under licence in Greece, Iran, Italy, Pakistan, Spain and Turkey. The MG3 began life as the MG42/59 in 1959, and after 1968 went into mass production as the MG3.
Bundeswehr soldiers with the MG3. The gunner is using the trigger extension grip for the gun's sustained fire mount. The litter of empty cases shows that this post-war clone of the MG42 has a high rate of fire. Its quick-change barrel is replaced after 150 rounds.

The MG3 fires from an open bolt and has a short recoil barrel with the bolt locking into the barrel extension via two rollers. Like the MG42, the MG3 has a quick change barrel. The normal drill is to replace it after a 150-round burst. However, in contact this rate can be increased to 200 to 250. As a GPMG the MG3 has a very high rate of fire - between 700 and 1,300 rpm.

The RPK-74
The Soviet Ruchnoi Pulemet Kalashnikova-74, or RPK-74, was developed along with the AK-74 assault rifle as a ten-man squad-level light-support weapon firing the new, small-calibre 5.45mm ammunition. The RPK-74 was adopted by the Soviet Army in the late 1970s and is still in use with the Russian Army today. The RPK-74 has a cyclic rate of 600-650 and a practical rate of 150 rpm. The maximum effective range is 460m/503yd.
The RPK-74 is similar concept to the British light support weapon: an infantry rifle with a longer barrel and bipod to give a squad an automatic weapon for engaging targets at longer range

Internally the RPK-74 is almost the same as the AK-74 rifle - a select-fire, gas-operated, rotating bolt-locked weapon - but it has a heavier and longer fixed barrel with a bipod, and redesigned buttstock. The RPK-74 can be fed from 45-round box magazines or standard AK-74 30-round magazines. Drum magazines holding 75 rounds similar in design to those of the RPK were also developed. They are much in demand with Russian troops in Chechnya.
Versions of the RPK-74 with a side-mount for the 1LH51 night-vision scopes are called RPK-74N. The first RPK-74s were manufactured with wooden pistol grips and fixed buttstocks, but current guns have polymer grips and side-folding polymer buttstocks.

Entering service in the late 1950s, the American M60 GPMG was designed towards the end of the 1940s. Its design drew on a number of German wartime developments including the MG42 machine gun and FG 42 automatic rifle. It had no gas regulator, which sometimes resulted in the gun jamming if fouled or, less usually, in a "runaway gun". This occurred when the working parts went back far enough to feed, chamber and fire a round but not far enough to be engaged by the sear, so that even if the pressure is taken off the trigger the gun keeps on firing. In these conditions the only option is to hold on to the belt to prevent it from feeding.

The M60 can be mounted as a sustained fire gun or on vehicles and has a quick-change barrel and integral bipod. Both the M60 and M60E3 have a cyclic rate of 550 rpm.
A grizzled US soldier in Vietnam has belts of 7.62mm ammunition ready for use for his M60, draped over a tree trunk to ensure that they do not foul in the mud on the jungle floor.

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