37-mm Aircraft Gun Matériel M4 - TM 9-240 War Department Technical Manual

1. Scope. — a. This manual is published for the information and guidance of the using arms and services.

b. In addition to a description of the 37-mm automatic gun M4, this manual contains technical information required for the proper use, care, and identification of the materiel.

c. Disassembly, assembly, and such repairs as may be handled by using arms personnel will be undertaken by any capable armorer.

d. In all cases where the nature of the repair or adjustment is beyond the scope or facilities of the unit, the responsible ordnance service should be informed in order that trained personnel with suitable tools and equipment may be provided, or proper instructions issued.

Figure 1. — 37-mm aircraft gun M4 — left side.

(1) Caliber, 37-mm or 1.457 inch.

(2) Weight of gun without magazine pounds.

(3) Weight of 30-round magazine do (4) Weight of 30- round magazine loaded do (5) Weight of 15-round magazine do (6) Weight of 15-round magazine loaded do — (8) Over-all length of gun inches.

(10) Muzzle velocity feet per second.

(11) Cyclic rate of fire shots per minute.

(12) Capacity of recoil mechanism ounces.

(1) Weight of one round pounds 1. 93 (2) Weight of 20 rounds in packing box do 61 (3) Dimensions of 20-round packing box inches —, 151/g by lliy 16 by 13% 2 3. Cautions. — Most aircraft guns differ from other guns in that because of their inaccessibility during flight, there is no possibility of their being serviced after the airplane has left the ground. It is therefore most important that an aircraft gun be very carefully cleaned, lubricated, and placed in working order before it is assembled in the airplane. The following points should be scrupulously observed:

a. All preservatives must be removed from the gun. To do this it is necessary to disassemble the entire mechanism, including the driving spring assemblies.

b. Whenever the tube is removed from or reassembled to the gun, the lock frame must be retracted. If this is not done, the extractor will be deformed and rendered useless.

c. The recuperator must be filled with light recoil oil, U. S. Army Specification No. 2-36D, to the proper level (par. 31). Failure to do so may result in severe damage to gun, airplane, and pilot.

d. The recuperator must not be disassembled except by authorized ordnance personnel, since it is very difficult to reassemble properly in the field.

e. Before the gun is installed in the airplane, its action should be tested carefully by hand.

4. Description. — The 37-mm automatic gun M4 is an aircraft weapon. It uses the energy of recoil to load, fire, and eject projectiles automatically. It consists of two distinct parts, recoiling and nonrecoiling. The recoiling portion is composed of tube, tube extension, recuperator piston rod, lock frame, and lock frame driving spring assemblies. The nonrecoiling portion consists of the trunnion block assembly, feed box assembly, and recuperator cylinder (fig. 2).

5. Functioning. — The functioning of the various members during the firing cycle is as follows (fig. 30):

a. When the firing button is pressed by the operator, it causes the solenoid on the top cover at the rear of the trunnion block to pull the trigger. The trigger pulls the trigger bar, rotating the top of the trigger lever to the rear.

Republished by Liber Copia LLC for convenient study and reference on any device.