SECTION I : DESCRIPTION

 1. CHARACTERISTICS.—The 37-mm gun, M1916, is a flat trajectory weapon of the field-gun type which fires highexplosive shells or low-explosive shells that weigh slightly more than a pound. Five general methods of transporting the weapon are—

1.  a. Gun and cart attached, drawn by mule or horse. 
2. b. Gun and carriage unlimbered, drawn on wheels by the gun squad. 
3. c. Gun disassembled into three loads consisting of gun and cradle, tripod, and wheels and axle, the first two loads being carried and the wheels and axle being pushed. 
4. d. Gun and carriage unlimbered and carried in a truck. 
5. e. Gun and carriage broken down for pack transport.

 DESCRIPTION.—

1. A. Barrel assembly.—(See figs. 1, 2, 3, and 4.) The barrel assembly consists of the following principal parts: Barrel; breech ring, which is screwed on the rear end of the barrel forming a recess for the breechblock; breech block, which closes the chamber for firing and carries the ex tractor mechanism and some of the firing mechanism; jacket and jacket shoe which form the rear support for the barrel, the shoe forming also a guide for the barrel during recoil; clip, which forms the front support and guide for the barrel. 
2. B. Cradle.—The cradle is located below and supports the barrel. It is provided with trunnions and a bracket for attachment to the carriage, and carries a bracket on the left side for attachment of the sight. The recoil cylinder of the cradle contains the recoil mechanism. A hole is provided through the front cap for filling the recoil cylinder with oil. On the right rear upper surface of the cradle is the drain plug which closes the overflow hole.
3.  C. Tripod.—The tripod comprises the following principal parts: Two trails, front leg, pintle, pintle socket, elevating mechanism, and traversing mechanism.
1. (1) The trails, right and left, are made of steel of channel iron sections. Riveted to the front of each trail is a trail head, and to the rear end a trail spade. Axle stay clamp blocks, movable in the mortises formed by the trail reenforcement plates, are provided to which the axle stays are hooked when the gun is on wheels. A traversing screw bush ing for attachment of the traversing screw through which this screw passes when the trails are closed is on each trail. Also on each trail is a lunette swivel through which the rammer is placed when the gun is drawn by hand, and a singletree eye which is used for joining the gun to the cart.
2. (2) In addition to the description given in (1) above which is common to both trails, on the left trail are two trail brace chain eyebolts for securing the trail brace to the trail. On the right trail are the front and rear shoulder guard brackets, front and rear sponge staff fastenings, and trail brace lock ing plate. The front and rear shoulder guard brackets carry the shoulder guard when it is not in position for firing. The sponge staff fastenings, front and rear, are for carrying the sponge staff. The rear fastening has a plunger and spring which hold the sponge staff in place. The train brace locking plate holds the trail brace when the trails are spread.
3. plate holds the trail brace when the trails are spread. (3) The front leg is attached to the pintle socket by two front leg pins. Two elevations in mounting are possible through provision of two different holes for the lower pin. Attached to the lower end of the leg is the front leg float, an enlarged bearing surface to minimize sinking in wet or loose soil when firing from the tripod.
4. (4) The pintle socket affords the central connection be tween tripod and axle by engaging the pintle socket bearing (by means of the stud formed on pintle socket). To it also is attached the front leg. The pintle socket and trails form a joint, the three parts being joined together by the pintle bushing which passes through them, forming a common axis pin
5. (5) The pintle, or gun mount, is in the form of a yoke, the upper ends being fitted to receive the cradle trunnions. The pintle is projected downward from the yoke, forming a pivot which fits into the pintle bushing. Projecting through the pintle bushing, the lower end is tapped to receive the pintle retaining plug which holds it in place. The front leg shackle is suspended from the pintle retaining plug to which it is fastened by the front leg shackle screw.
6. (6) The elevating mechanism is supported on the rear end of a Y-shaped frame which is secured to the pintle at its upper and lower ends. The elevating screw passes through the elevating screw nut which is threaded to receive it, and it in turn is pivoted in the elevating screw nut bracket. Ele vation is secured by turning the elevating screw handwheel attached to the upper end of the elevating screw.
7. (7) An elevating screw nut clamping lever is provided below the elevating screw nut to lock the elevating gear in po sition. Above the handwheel is the elevating screw latch housing which engages the elevating screw latch catch bracket on the under side of the cradle.
8. n the under side of the cradle. (8) Traversing is accomplished by lateral movements of the elevating screw and nut bracket and the Y-shaped frame, the front ends of the latter being securely attached to the pintle carrying the cradle and barrel. In rear of the point where the elevating screw nut pivots, the elevating screw nut bracket forms a fork and engages the traversing screw nut housing. A traversing screw nut threaded to engage the traversing screw is placed in the traversing screw nut hous ing, and may be revolved by a traversing handwheel at tached to the nut. This turning causes the lateral movement or traverse as the traversing screw is prevented from rotat ing by the traversing screw lock located in the right travers ing screw bearing.
4. D. Axle and wheels.—The axle has a spindle at each end to which the wheels are fitted. At its center on the lower side is the pintle socket bearing into which the socket stud is placed when the tripod is attached to the axle. An axle cou pling pin, attached to the axle by a chain to prevent loss,passes through a hole in the socket stud, securing the tripod to the axle. On either side of the pintle socket bearing an axle stay is attached. These are hooked into the axle stay clamp blocks on the trails and assist in securing the axle to the tripod. The axle lock which is assembled underneath the pintle socket bearing fits between the flanges of the pintle socket or may be swung out of engagement with it, and is held in the desired position by inserting the axle coupling pin on the proper side of the axle lock stop. When the gun is supported on the wheels in firing the axle lock must be swung out of engagement with the pintle socket (un locked) . At all other times, and especially during transpor tation of the gun on wheels, the axle lock should be engaged with the pintle socket (locked).