DESCRIPTION

The Lewis aircraft machine gun is designed for flexible mounting. As may be seen from the photograph.

It differs from the Army type in that the radiator has been removed, and a spade grip is used instead of a regular butt stock, and it is fitted with a special mounting yoke and recoil check. The gun is fed from a magazine holding 97 rounds.

The weight of the gun is 18 pounds, and the rate of fire, 600 shots per minute. The ground type gun is described in Ordnance Pamphlet No. 1931.

These guns are usually installed in pairs or singly on a flexible mount.

Lewis guns are, packed for shipment in a wooden box 40 inches by 4 1/2 inches by 7 3/4 inches deep, containing one gun and its spare parts. The magazines are packed in a wooden box 9 1/4 by 11 1/4 inches by 9 1/4 inches deep containing three magazines. Six magazines in containers are supplied with each gun.



POINTS TO BE OBSERVED BEFORE A FLIGHT

The gun must be, in perfect operating condition, all parts cleaned and properly oiled.
The parts which need particular attention in oiling are:

Bolt.
Worm of feed operating stud.
Head of piston.
Striker post.
Slot in feed arm for feed operating stud.
Feed pawl (at pivot).
Stop pawls (at pivot).
Meeth on mainspring casing and on rack.
Threads on gas chamber land and gas regulator cup.

Make sure that the hole in the gas chamber gland registers with the hole in the gas chaimber, and the gas cylinder connection is tightly screwed onto the gas chamber.

See that the large gas port (No. 4) in the gas regulator cup is turned to the rear, thereby giving the maximum gas pressure on the, recoiling parts.

The gun ordinarily operates with a spring tension of from 12 to 14 pounds. Due to the adverse conditions under which the gun works it may sometimes be necessary to reduce the tension to insure, operation, but it should never be made less than 10 pounds.

Work the mechanism slowly back and forth several times by means of the charging handle to see that it runs smoothly.

The magazines for the Lewis gun should be very carefully inspected before being used, since a defective, magazine is almost certain to give trouble. A little oil should be applied to the bearings and to the magazine latch. The latter should be tested to see that its spring works freely, as cases have been found where the latch did not return to its proper position to lock the magazine to the magazine post.

The magazines should be spun on a loading handle to see that they revolve easily. They should then be placed upon the magazine post and rotated, in order to make sure that no part of the rim rubs on the receiver or feed cover.

The magazine gauge (see Fig. 10) should be used to test the rim of the pan and t he, position of the, interior separator pins. The pins should be examined f or straightness and firmness.

When not in use magazines should always be kept in con tainers to prevent their becoming damaged or dirty. As a general rule, they should not be piled on each other, but if it is necessary to do this, they should be turned with the hollow side, downward and arranged evenly. This will obviate damage to the rims of the pans.

Make sure that the fixed sight, where supplied, is rigid.
See that the gun is firmly attached to its mount.
Make sure that the Bowden wire control, if used, will release the trigger.

RECOIL CHECK

The recoil check is screwed to the muzzle of the gun, and with an opening for the bullet to pass through. The rear surf ace of the disk is so shaped as to deflect the gases to the rear.

The operation of the recoil check is as follows:

A portion of the gases issuing from the muzzle of the gun strikes the rear surface of the disk and is deflected back (as shown by the arrows in the cross section view). This gives a forward im ulse on the recoil check which tends to counterbalance the recoil of the barrel. In this way the recoil of the gun is limited to about 4 pounds.

TEST GAUGE FOR LEWIS MAGAZINE

The gauge consists of a steel plate punched as shown in figures 10 and 11. A loading handle is put through the large hole and inserted in the magazine center as in loading. The gauge is then turned so that the interior separator pins, appear two by two in the small openings. This checks the distance from the center and the distance apart of the pins. The outside edge of the corrugations stould appear opposite the small slit. The wider slit shows the tolerances which may be accepted; the inner or outer edge of the corrugation .should be included within the inner or outer edge of the slit.


SHELL DEFLECTOR BAG

The empty shells from the Lewis gun are caught in a shell deflector bag which is clamped to the receiver of the gun. This bag is made of.heavy canvas reinforced with wire and held in a distended position by three wire loops. The bottom of the bag is closed by a flap which may be unclasped to permit the removal of the shells. The bag will hold 97 rounds, the contents of one magazine.

ELECTRIC HEATER FOR LEWIS GUN

In order to prevent stoppages of the gun due to gummed oil caused by low temperatures when flying at high altitudes electric heaters are furnished for the Lewis aircraft machine gun, consisting of a resistance grid surrounded by insulating material.

The heater is riveted to the under side of the feed cover and is connected with a plug on the top of the cover which provides for connections with the leads. The heater consumes 36 watts at 12 volts and is fed from the generator which supplies the lighting system.