/ FLIGHT, July 27.

A MODERN AIRCRAFT GUN i

Features of the Pickers K Machine Gun as Supplied to the R.A.F. : Compactness

and High Rate of Fire

DE S P I T E the renaissance of shell-firing a r m a m e n t and the marked t rend towards guns of larger calibre, the small-bore, high-speed machine gun still holds pride of place in the aeronaut ical a rmoury . Great

Britain, more than any other country, has developed in­stallations of mult iple machine guns, bo th fixed and in power-driven tur re ts . Flight, with the co-operation of Fi t . L t . T . Le G. Pynches , of Vickers-Armstrongs, was recently permit ted to visit t he company ' s factory a t Cray-ford and to inspect the Vickers Class K machine gun, one of the latest weapons to be adopted by the R . A . F . , and probably the most successful gun of i ts type in the world.

On the top floor of the immense camouflaged main build­ing at Crayford we met Major Kilner, general manager, of

BjfajL

Action of the K gun : (I) Piston and breech block have been propelled forward by the tension of the main spring. Breech block is in locked position, and the cartridge has

been fired by the piston having pushed forward the firing pin.

(2). Piston and breech block have commenced to move backwards. The rear of the breech block has been brought downwards from engagement with »he locking shoulder.

(3) Piston and breech block in their rearmost position. The piston has been brought to rest against the buffer and is about to go forward

the Southern Works , who handed us over to Mr. P . R. Higson, the chief designer, and Mr. R. Wan-for, product ion manager.

The unique features of the Model K were ex­plained by Mr. Higson with the aid of a sectioned gun. This weapon, which has a muzzle velocity of 2,400 f t . / s e c , is qui te ex­ceptionally compact , and has a ra te of fire between 950 and 1,200 rounds a minute . The unusually smooth action, combined wi th a low recoil force, makes the gun easy to con­trol and aim with accu­racy. There are no exter­nal moving par t s which might injure the gunner, and the gun has a mini­m u m of exposed surface. Ammuni t ion is fed from a spring-loaded drum which normally holds 60 or 100 rounds, bu t which, for fixed installation, can accommodate 300 or 600 rounds in very large, flat magazines. Instal led in a fixed-gun fighter, weapons of this sort score over belt-fed models in t h a t the feed ar rangements a r e n o t affected by " G . " The gun m a y be dismantled in a few seconds wi th the aid of a cartr idge and a pen­knife.

The action c a n be studied in the accompany­ing diagrams. When the gun is cocked (by pulling back a handle on the left-hand side), t h e breech block is retained a t the rear of t h e " r e c e i v e r , " or breech casing, on a projec-

FLIGHT, July 27, 1939. ?

The complete Vic-kers K gun with ring-and-bead sight. A reflector sight is now fitted. The bag collects the

"empties ."

tion at the back of a piston. On the trigger being pressed, this piston is propelled forward by the force of the com­pressed main spring, carrying with i t t he breech block, which pushes a cartr idge from the magazine into the barrel chamber. As the piston continues to move forward, the rear of the breech block is engaged by an angular pro­jection on t h e rear of t h e piston, and is forced upwards to abut in front of a locking shoulder on the main body of the gun. Thus , the breech block is positively locked against the base of the cartr idge in t h e barrel chamber . A floating firing pin in the breech block is then struck by a projection on the rear of the piston and the cartr idge is fired.

As the bullet is nearing the muzzle a port ion of the pro­pelling gases escapes downward through a small hole in the barrel, and is deflected by a gas block to impinge on the head of the piston (housed benea th the rear pa r t of the barrel), driving i t t o the rear, compressing the main spring, and unlocking and wi thdrawing the breech block from the barrel.

During the rearward movement of the breech block the empty case is extracted from the barrel and ejected into a bag on t h e side of t h e gun. The cycle of operat ions is repeated unti l t he trigger is released or the ammuni t ion exhausted. A safety catch is incorporated in the hand­grip.

Complete wi th flash el iminator the gun is 40m. long, and, fitted with sights, deflector and bag, weighs 22 lb .

Although normally used as a directly operated free gun the Model K can have remote control for tur re t or wing mounting, or can be fitted with a stock for ground defence.

Considering the comparat ively small section of the main building devoted to K-gun product ion, t h e ra te of ou tpu t is highly creditable. Space does not permi t a description

of the manufactur ing pro­cesses, though it may be ment ioned t h a t there are 140 operations on the " receiver " alone. Mr. Wanfor explained t h a t girls have been found best suited to perform a number of the more delicate operat ions.

On completion, the guns are sent down an electrical hoist to the proving ground, where two proof rounds are fired. These cartridges have'

a 25 per cent, more powerful charge t han s tandard ammuni t ion . The guns are then str ipped for inspec­t ion, reassembled, and are passed ou t for " a u t o ­mat ic " tests in a horizontal position, a t 80 deg. elevation and 80 deg. depression. Nex t t hey are s tr ipped and cleaned prior to the accuracy trial, which is conducted in the underground range. After a final strip they are inspected both by t h e com­

pany ' s representatives and the Air Ministry. Thus is reliability in service ensured.

Showing now the K gun can be used from the shoulder. It may also be mounted on a tall tripod for anti-aircraft work.

Opening and Re-opening

A PUBLIC-USE licence has now been issued for the new Oxford aerodrome, which lies about two miles south-east

of Woodstock. This aerodrome, which is controlled by the Oxford Corporation, has a maximum run of 1,425 yd. in the S.E.-N.W. direction, and a minimum run of 1,020 yd.

At the same time a private-use licence has been reissued for East Heslerton aerodrome, near Scarborough. Mr. J. R. Micklethwait, who is a director of the Yorkshire Aeroplane Club, is taking a special interest in this aerodrome with the idea, we believe, of starting a new C.A.G. centre there East Heslerton has been officially out of action during the last year or so.

A few days later a private-use licence was also issued for Swindon aerodrome at Watchfield. This is controlled by Mr. A. J. Walter, who is the agent in this country for the Piper Cub and is operating a Civil Air Guard club there.

Using Reverse /^\NE particularly valuable use for reversible-pitch airscrews ^ is not usually considered—that in small-space manoeuvring of multi-engined flying-boats. By adjusting the airscrews on one side to reverse pitch, leaving the other two in fine pitch, it would be possible to turn a flying-boat almost within its own

length. At the same time, by reversing all four airscrews, rapid deceleration, when necessary, would also be possible.

The Propeller Division of the Curtiss Wright Corporation claims that its electrically operated reversible-pitch airscrew has reached a practical stage in its development, which has been carried out with the co-operation both of the Civil Aero­nautics Authority and the United States Navy. Apparently the increase in weight is negligible. The necessary pitch-change is accelerated by the voltage booster unit, which is also used for rapid feathering.

A Sports Major

LUTON AIRCRAFT are at present working on a sports ver­sion of the Luton Major. This, it will be remembered,

is a cabin tandem-seater strut-braced high-wing monoplane, and the new sports model will be generally similar. The engine fitted, however, will be a Gipsy Minor, giving an addi­tional 30-odd h.p. to that of the Mikron fitted to the standard Major; the undercarriage will be of the cantilever type; and the wing area will be reduced from 35ft. to a little over 30ft.

The dimension figures and loadings will be : Span, 30ft. 2in.; length, 23ft. gin.; weight empty, 700 lb . ; and all-up weight, 1,220 lb. I t is estimated that the top speed will be 126 m.p .h . ; the cruising speed, 112 m.p.h . ; the landing speed, 47 m.p .h . ; and the range at cruising speed, 325 miles.