Ammunition feeds

The earliest machine guns relied on gravity to feed ammunition to the weapons. Typically, there would be some form of vertical guide above the gun into which the cartridges would slot, properly aligned with the chamber. The lowest cartridge would be suspended just above the bolt, or pressed against it, so that after recoiling to the rear, the bolt would push the next cartridge into the chamber on its return.

Reflector Screen

Ant i GJ&re hood

Sunscreen knob

Mk9 Reflector Sight

Horizontal adjustment

Sunscreen Vertical adjustment housing knob

/resistance reta/ning button

Aircraft reflector sight, British, WW2 (Courtesy: R.W.Clarke)

Reflector Screen

Ant i GJ&re hood

Sunscreen knob

Horizontal adjustment

Sunscreen Vertical adjustment housing knob

/resistance reta/ning button

CARTRIDGE HOLDING PAWLS

MAGAZINE OR HOPPER

40mm Ww2 Breech

CARTRIDGE HOLDING PAWLS

MAGAZINE OR HOPPER

INCOMING ROUND

Molins Automatic Gun

STAR WHEEL FEEDERS

STAR WHEEL AXLE

STAR WHEEL AXLE

STAR WHEEL FEEDERS

INCOMING ROUND

FEED SLIDES

FEED SLIDES

40mm Bofors

FEED SLIDE OPERATING CAM GROOVE

BREECH

CARTRIDGE FEED PAWLS

STAR WHEEL LATCH

FEED SLIDE OPERATING CAM GROOVE

BREECH

CARTRIDGE FEED PAWLS

STAR WHEEL LATCH

Gravity feed for Bofors 40mm gun ( BuOrd, VSN)

RAPID FIKE

Bofors 40mm Missouri

Gra vity feed for Mo I ins

6pdr gun (BuOrd, USN)

Gra vity feed for Mo I ins

6pdr gun (BuOrd, USN)

Rear view of Bofors 40nun 101-round magazine

(Courtesy: Celsius)

This form of gravity feed remained popular in larger cannon calibres for many decades, as it is simple and reliable. Ammunition for the original Bofors gun, for example, was held in groups of four by a light-alloy clip fitting around the head of the case. Each clip was dropped into the guides above the gun as required. In modern versions, large-capacity magazines are available together with automatic clip handling, but gravity is still utilised.

The main problem with the basic version of this method is that only a small quantity of ammunition is ready to fire at any given moment. Continuous fire requires loaders who are kept very busy scurrying to and fro, feeding the beast. It is therefore only appropriate for circumstances where the gun is stationary and there is plenty of room around it for the gun crew to operate without much fear of being gunned down - in other words, in land- or ship-based anti-aircraft weapons.

The many and various means of providing an

Right magazine _a_

Left magazine

Vertical (Hap) feed unit

Vertical Magazine Automatic Loader

Compartment feed levers (11 in total)

Right lateral feed device

Round in flap position Round in ramming position Automatic loader

Right magazine _a_

Compartment feed levers (11 in total)

Left lateral feed dcvice

Vertical (Hap) feed unit

Shift tongue

Left magazine

Lateral feed device for Bofors 40mm 101-round magazine

(Courtesy: Celsius)

Bofor 40mm Clip

extended period of uninterrupted fire account for the different types of ammunition feed currently in use. In larger calibres, this has been achieved by retaining gravity feed but arranging a device which holds several stacks of cartridges side by side, from which rounds are moved to the breech in turn. This method was used in the 57mm Molins gun carried by Coastal Commands Mosquito XVIII anti-submarine aircraft, in which gravity was assisted by a spring-powered arm on top of each bank, with electrical power being used to shift the banks into position. A modern example is the Bofors SAK 40/70E naval gun, which has a 101 -round magazine consisting of ten columns.

In smaller calibres, detachable box, drum or pan magazines have sometimes been used. In a box magazine the cartridges are stacked on top of each other, in one or two rows. A drum is a cylindrical container which holds the rounds parallel to each other. A pan magazine (sometimes also referred to as a drum) is circular but flat, with the cartridges arranged radially, all pointing inwards. All of these types usually have an internal spring which keeps the cartridges pressed against the open end of the magazine; they are stopped from falling out by lips which only permit them to slide out lengthways. A less common variation with drum or pan magazines is for them to be rotated by the gun s mechanism, as in the Lewis RCMG, or by some other external power source.

Advantages of magazines are that the ammunition is protected from damage and collecting dirt, and the feed will work at any angle or even in a

Hispano Drum Magazines

Drum magazine on Oerlikon S (Courtesy: MoD Pattern Room)

Drum magazine operation

W-SHAPED TENSION SPRING

CARTRIDGE SPACER RING

STATIONARY OUTER FEED DRUM

FEED ROTATING CAM

STATIONARY OUTER FEED DRUM

FEED ROTATING CAM

W-SHAPED TENSION SPRING

20mm Feed Sprocket

BOLT

FEED SPROCKET

INCOMING ROUND

BOLT

FEED SPROCKET

INCOMING ROUND

INNER DRUM ROTATING SPROCKET

INNER DRUM ROTATING SPROCKET

CARTRIDGE SPACER RING

Vertical Bolt Feeder

ANTI REVERSE RATCHET

OPERATING ROD

BARREL

Cam on Bolt Rotates Feed Drum and Feed Sprocket.

ANTI REVERSE RATCHET

OPERATING ROD

BARREL

Cam on Bolt Rotates Feed Drum and Feed Sprocket.

violently manoeuvring aircraft. The main disadvantage is of course that their capacity is necessarily small, both because of their bulk and because there is a limit to the amount of work a spring can reliably be expected to do.

The simplicity and low cost of the box magazine has led to it becoming the standard ammunition feed used by virtually all military rifles, submachine guns and pistols today. However, they rarely hold more than twenty rounds in large calibres, which once again calls for an energetic loading crew and limits the effective rate of fire. One of the best examples is the German 2cm FlaK 30 and FlaK 38 - the standard wartime light AA weapons

- which normally used twenty-round boxes.

The radial pan magazines were at one time popular in RCMGs, but not in larger calibres except in special circumstances, the necessarily large diameter normally being a deterrent. Parallel drum magazines have been far more common. The best known is probably the original Oerlikon S 20mm cannon, used by the Royal Navy from the Second World War until very recently, which used a sixty-round drum. The earliest marks of 20mm Hispano aircraft cannon of the 1930s also used a drum of this capacity, as did most of the Luftwaffe's 2cm MG-FF. However, while the need to change drums at frequent intervals was just about acceptable in a

WINDER PUTS FEED SPRING UNDER TENSION

MAGAZINE COVER ROTATES ALONG WITH CARTRIDGE SPACERS

WINDER PUTS FEED SPRING UNDER TENSION

MAGAZINE COVER ROTATES ALONG WITH CARTRIDGE SPACERS

Bev Fitchett Guns Magazine

CLOCK TYPE MAGAZINE SPRING

COVER LATCH

CARTRIDGE SPACERS

SPIRAL COIL OF WIRE GUIDES PROJECTILES

TO GUN

Spring-Loaded Magazine Positions Cartridges in Front of Bolt

CLOCK TYPE MAGAZINE SPRING

COVER LATCH

CARTRIDGE SPACERS

SPIRAL COIL OF WIRE GUIDES PROJECTILES

TO GUN

Spring-Loaded Magazine Positions Cartridges in Front of Bolt

Pan magazine operation (BuOrd, USN)

warship, the capacity soon proved inadequate in attention turned to belt feeds.

aircraft use. Larger drums of up to 100 rounds were

Belt feeds were actually developed very early in developed, but their bulk counted against them and the life of machine guns, and were utilised by the original Maxim. In this weapon, as with the early Vickers derived from it, the belt was of canvas with pockets sewn into it for the cartridges. As the early military cartridges were rimmed, this meant that they had to be withdrawn to the rear by the loading mechanism before being pushed forward into the chamber. Canvas also had the problem of being affected by moisture. Finally, the existence of the emptied belt flapping about clearly proved a nuisance in aircraft applications, prompting the introduction of the disintegrating link steel belt.

As its name suggests, the belt is formed of individual steel links which clip the cartridges together. The cartridges form an integral part of

Pan Magazine

Pan magazine for experimental .5" BSA

(Courtesy: MoD Pattern Room)

Pan magazine for experimental .5" BSA

(Courtesy: MoD Pattern Room)

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