Construction of Field-guns.

DETAILS OF CONSTRUCTION OF FIELD-ARTILLERY GUNS (LATEST MODEL).

The guns described in this and the next chapter are built-up guns made of low steel, and all the parts are tempered in oil.

The tube enters the jacket from the front[3] and has shoulders upon it, which come in contact with corresponding shoulders in the jacket. These shoulders prevent any forward movement of the tube or rear movement of the jacket.

The tube tapers from in front of the jacket to the muzzle, which ends in a swell.

The exterior of the jacket is made up of a series of tapering surfaces.

On the interior surface, starting from the rear end, there are first, the seat for the carrier-ring in the jacket, which also contains the slotted and threaded sectors for holding the breech-block; in front of this is the tapering gas-check seat in the tube; and forward of this is the cylindrical powder-chamber, which is connected to the shot-chamber by a slope. The shot-chamber also is cylindrical and connected with the bore by a slope.

The vent being axial in the model of '90, enters the powder-chamber through and along the axis of the spindle of the obturator. In front of the gas-check seat in the model of '85 there is a cylindrical surface leading to the ellipsoidal powder-chamber, which is connected with the shot-chamber by a slope, and the radial vent enters 12½ inches from the rear face of the jacket and at the maximum diameter of the powder-chamber. The vent-piece, made of copper, is screwed into position, the part projecting above the surface of the piece being rectangular.

The Breech Mechanism.

The principal parts are the breech-block, the carrier-ring, the obturator, the lever-handle, the bronze handle, and the vent-cover.

The Block, Fig. 30, is threaded for a distance of four inches from its forward end, and the circumference of the thread is divided into six equal parts. The threads of the block are removed along three alternate sectors, as is usual in the interrupted-screw fermature, to allow the block to slide in the corresponding slotted sectors in the jacket (or base-ring in earlier model).

The threaded sectors engage in the corresponding slotted sectors in the breech-block, but one sixth of a turn of the block will engage the screw-threads of both.

The interior of the block is bored out to form the obturator-spindle recess.

At the end of the block are two lugs for the lever-handle. On the right one is a shoulder which limits the motion of the lever-handle.

The Nose is the front end of the block, slightly reduced in diameter in order to partly enter the gas-check seat.

The Stop-groove, into which the stop on the carrier-ring enters, is in the planed sector on the left-hand side.

The Latch-groove (Fig. 31) is in two parts, one longitudinal (d), at the front end of the block, and the other transverse (a), at the rear end. The stem of the latch drops into the front groove (e) when the block is withdrawn, and into the rear groove (b) when the block is revolved into its firing position, in each case unlocking the carrier-ring from the jacket—in the first case, so that it maybe swung back; in the second, to prevent the breaking of the latch when the gun is discharged.

The Locking-recess (e) is at the front end of the longitudinal latch-groove. The stem of the latch drops into it when the block is withdrawn, and thus locks the block positively to the carrier-ring.

The Guide-groove is the cylindrical recess at the rear of the block in which the guide-sectors move when the block is rotated.

The Guide-sectors (b, Fig. 32) are three projections from the interior of the carrier-ring (h), which fit in the slotted sectors of the breech-block and guide it during its motion through the carrier-ring.

The Latch-cover (i) is a separate piece which covers the latch and its spring, and is secured to the carrier-ring by two screws (j). On removing this plate the latch and spring can be taken out.

The Latch (f in Fig. 32) fits in a recess in the carrier-ring on the right side. It is acted on by a spring (b, Fig. 33), which pushes it constantly toward the axis of the carrier-ring. Its inner end or stem (a) rests on the surface of one of the slotted sectors, except at the end of its travel, when it drops into the corresponding recess in the block. As long as its stem rests on the surface of the sector its outer end or nose projects beyond the exterior surface of the carrier-ring, and, entering a recess in the jacket, locks the carrier-ring to the jacket. When the stem drops into its recesses, the nose of the latch is withdrawn by the action of the spring and the carrier-ring is unlocked. The front face of the latch has a recess (h), into which fits a hardened stud (s) that is screwed into the rear face of the jacket. This stud acting against the recess lifts the latch out of its locking-recess in the breech-block, and holds it in a position such that the stem can pass up the inclined groove. In order that the stud may act on the latch, a hole (g) is drilled through the front face of the carrier-ring for the stud to pass through.

The functions of the latch-spring have already been explained.

The Stop (c, Fig. 32) enters the carrier-ring on the left side between the lugs (e), and projects beyond the bore of the carrier-ring, entering a groove in the breech-block which is cut for it. This stop limits the travel of the block to the rear in withdrawing it, and also limits its rotation.

The Hinge-pin enters the lugs (e) of the carrier-ring and a corresponding lug on the jacket from below, and the carrier-ring swings around it in opening. The bore is the diameter of the ring across guide-sectors.

The exterior taper forms the surface of contact of carrier-ring with jacket.

The lugs (e) are the bearings for the hinge-pin. The carrier-ring, as its name indicates, carries the breech-block when the latter is withdrawn, and by means of it the block may be swung round out of the way for loading.

The principal parts are: the spindle (a); the front cup (f); the rear cup (f'); the pad (g); the spring (j); the nut (h); the spline-screw (k).

The spindle has a mushroom-shaped head (b), and a stem, which extends through the breech-block and terminates in a screw-thread. The breech-block is recessed correspondingly. In guns with axial vents, the vent (c), 0.2 inch in diameter, passes through the axis of the spindle, and the copper bushing (d) is inserted by pressure at the front end.

The front and rear gas-check cups are of steel, and hold between them a plastic pad made of certain proportions of asbestos and tallow and covered with canvas (with disks of copper (m) on either side in the revised model,) and a diagonally-split ring (n) of steel is used to cut off the escape of gas.

A spiral spring (j) surrounds the stem of the obturator at the rear of the block, and bears against a shoulder on the block and a nut (h) on the screw-thread of the spindle. This spring, which acts to press the spindle back, keeps the cups and pad in place, takes up any set of the pad due to firing, and prevents the fracture of the screwed end of the stem.

The spline-screw (k) holds the nut on the spindle in position and prevents its unscrewing when the pad sticks in its seat after firing.

The principal parts are (Fig. 35): the spindle (a); the gas-check ring (f); the spring (e); the obturator-nut (d); the locking-nut (d'), or the spline-screw.

The Spindle has a head (g) at the forward end, its surface being plane and its sides conical, with the larger diameter of the cone in front. The vent (c), 0.2 inch in diameter, passes through the axis of the spindle, and the copper bushing (c) is inserted by pressure at the front end.

The Gas-check Ring (f) is nearly triangular in section, coming to a point at the front. It fits accurately on the conical surface of the head of the spindle, and is slightly longer in the direction of the axis of the bore than this head. Its rear surface rests against the front surface of the block, while the rear surface of the head is not in contact with this front surface, and can only be brought in contact with it by a heavy pressure, which will expand the gas-check ring.

The Spring (e) acts against a shoulder in the block and a corresponding shoulder on the obturator-spindle, and tends to press the spindle forward.

The Obturator-nut (d) prevents the action of the spring from forcing the spindle too far forward, and also regulates the tension of the spring.

The spline-screw acts as in the de Bange system. This screw is used in place of the locking-nut (d') shown in figure.

THE LEVER-HANDLE.

(See Fig. 37.)

This handle (h) acts as a lever to rotate the block, its head acting as a cam to withdraw the block and obturator when the latter sticks after firing, and to lock the block in the carrier-ring and prevent rotation during firing. It is supported in the lugs (l) of the breech-block by a pin (e) and rotates with the pin; to which it is secured by a screw entering vertically. The head of this pin has a projection (a) which strikes against the corresponding stop on the right lug and limits the motion of the lever-handle.

THE BRONZE-HANDLE.

(See Fig. 37.)

This handle (g) is attached to the breech-block by two screws. Its purpose is to assist in withdrawing and pushing in the breech-block.

For Axial Vent.—A radial slot (a, Fig. 36) is made in the rear part of the breech-block, in which slides a piece of metal (b) having a pin (c) projecting from its forward face next the gun. This pin fits into a groove (d) cut in the rear face of the carrier-ring, which is eccentric at its lower end, so that when the block is placed in firing position the slide is raised and the vent uncovered.

For Radial Vent.—This consists of a long arm, secured in position on top of the gun so that it can slide. The under side at its rear end has a slight projection, which engages over a shoulder on the lever-handle. When the lever-handle is raised a shoulder on it bears against the end of the arm, pushes it forward and covers the vent; when the block is in firing position and the lever-handle is lowered the shoulder bears against the projection and draws back the arm, thereby uncovering the vent.

Suppose the breech closed and the gun ready for firing. In this position the threads of the breech-block are engaged in the threads of the jacket (revised model) or base-ring (model '85); the gas-check is in its seat; the lower end of the latch is at the end of the transverse groove in the block; the nose of the latch is withdrawn from its recess in the jacket, and the carrier-ring is unlocked; the lever-handle is vertical, its cam in the recess in the carrier-ring, and its lower end in the recess in the jacket.

To Open the Breech.—Grasp the lever-handle (h, Fig. 37) with the left hand, thumb down, and raise it until it strikes the stop, then rotate the block as far as possible to the left; lower the lever-handle: its cam (d), acting against the surface (r) of the carrier-ring, will withdraw the gas-check if it sticks in its seat. This rotation of the block pushes the latch into its recess and locks the carrier-ring to the jacket. Grasp the bronze-handle (g) with the right hand, thumb to the right, and withdraw the block until it comes up against the stop. In this position the stem of the latch drops into the locking-recess, locking the block to the carrier-ring, and at the same time unlocking the carrier-ring from the jacket; swing the block and carrier-ring around to the left and insert the projectile and charge.

To Close the Breech.—Seize the bronze-handle with the right hand, thumb to the right, and swing the carrier-ring and block around until the carrier-ring is in its seat, grasping the lever-handle with the left hand, thumb down, at the same time, and raising the handle until it strikes the stop. The carrier-ring should be brought up to its seat sharply, but without slamming, and should be held firmly for an instant, otherwise the ring may start back slightly from the jar and the retracting-stud fail to hold the latch-pin high enough to allow the block to move forward.

When the carrier-ring strikes its seat the retracting-stud enters the hole in the front face of the ring, and, acting on the recess in the latch, lifts the latch to its travelling position, that is, lifts it out of the locking-recess and holds it in such a position that when the block is pushed forward, the lower end of the latch will strike the inclined surface at the front of the longitudinal groove.

Raise the lever-handle until it rests against the stop, and push the block forward until it stops. During this travel the lower end of the latch has moved up the inclined surface of the longitudinal groove and has locked the carrier-ring to the jacket.

Revolve the block one sixth of a turn until it strikes the stop; lower the lever-handle to its proper position, when everything will be in the condition first described, the vent will be uncovered, and the gun will be ready for firing.

When the block is revolved one sixth of a turn the lower end of the latch gradually drops into its groove, unlocking the carrier-ring, which remains so during firing.

INSTRUCTIONS FOR DISMOUNTING.

1. Raise the lever-handle and turn the breech-block to the left.

2. Take out hinge-pin screws and remove the hinge-pin.

3. Withdraw the breech-block with carrier-ring.

4. Take out the latch-cover screws and remove the latch-cover, latch-spring, and latch.

5. Take out the stop-screw and remove the stop.

6. Take off the carrier-ring.

De Bange Obturator.

7. Remove the spline-screw and take off the nut.

8. Take out the spindle.

9. Take out the spring.

10. Take off the obturator cups and pad.

Freyre Obturator.

7. Remove the spline-screw and take off the nut.

8. Take out the spindle.

9. Take out the spring.

10. Take off the gas-check ring and face-plate.

INSTRUCTIONS FOR ASSEMBLING.

De Bange Obturator.

1. Put the obturator cups and pad in place on spindle.

2. Put in the spring.

3. Put in the spindle.

4. Screw on the nut, and put in the spline-screw.

Freyre Obturator.

1. Put the gas-check ring and face-plate in place.

2. Put in the spring.

3. Put in the spindle.

4. Screw on the nut, and put in the spline-screw.

5. Put the carrier-ring on the breech-block.

6. Put in the stop and screw.

7. Put in the latch, the latch-spring; put on the latch-cover and screws.

8. Insert the breech-block with carrier-ring into the gun.

9. Put in the hinge-pin and screws.

10. Lock the block.

Experiments are now being made with the view of introducing metallic ammunition, and it is possible that a breech mechanism similar to the Driggs-Schroeder or the Gerdom will be adopted. A general description of each is therefore given, and also the proposed method of supplying ammunition.

The breech-block (b), weighing 31 lbs., has bands (c) on top and sides that fit in corresponding grooves in the jacket; these bands have an inclination of 2½ degrees to the front and upward to secure complete obturation and facilitate locking and unlocking.

There is a transverse hole (i) through the block for the main bolt (d); it is lengthened in a nearly vertical direction so that the first motion of the operating-handle causes, by the action of the main cam (e), the block to descend and disengage the bands from the grooves in the breech, after which the block rotates to the rear and rests on the tray. Guide-bolts (k), screwed through each side of the curtain, project into guide-grooves (l) cut in each side of the block and confine its movement.

The main cam, firing-pin and spring, and sear and sear-spring are contained in the block, the front face of which bears a heavy removable plate (a).

The firing-pin has under its rear part full-cock and half-cock studs; and the sear, actuated by its spring, presses up against it and engages the studs in succession as the firing-pin is forced to the rear by the action of the main cam against the lug on the under side of the firing-pin. The point of this lug always rests in the circular groove in the upper rear face of the main cam.

The extractors (j), one on either side, lie flat against the rear face of the tube of the gun and in recesses in the front face of the block. They revolve on pivots which work in recesses in the curtain. The rear sides of the tails of the extractors and the lower front corners of the breech-block form cam surfaces so arranged that when the block rotates to the rear the extractors extract and eject the cartridge-case.

The spring lock on the handle prevents the main bolt and block from moving, when the breech is closed, under stress other than that applied directly to the handle.

TO DISMOUNT.

1. Back out the guide-bolts far enough to clear the guide-grooves. 2. Half-cock. 3. Take off handle. 4. Tap the main bolt gently to start it and withdraw it completely, supporting the block with the hand. 5. Lower the block out of place, tilting it slightly to the rear so as to clear the extractors.

THE BREECH-BLOCK BEING OUT, TO TAKE THE MECHANISM APART.

1. Full-cock the firing-pin before removing the face-plate. 2. Remove face-plate. 3. Ease firing-pin forward and remove finger-catch. 4. Take out main cam, firing-pin, and spring. 5. Push sear-plug in a little, turn it until the stud is fair for coming out, and remove it and the sear and spring.

TO ASSEMBLE THE MECHANISM.

Proceed in the reverse order. Put in successively the firing-pin spring, the firing-pin, and the main cam. The front side of this cam is marked "out." The firing-pin must be full-cocked before putting on the face-plate and then let down to half-cock. An arrow on the head of the main bolt being brought in line with the arrow on the curtain indicates the proper "square" for the hexagonal bearing in the cam.

Gerdom Rapid-firing Breech Mechanism.

The breech-block has two threaded and two plain sectors (each 90 degrees) with corresponding sectors in the breech of the gun, so that the block is locked or unlocked by a quarter of a turn. The block contains a firing-pin which, with its spring, is inserted from the front end of the block, which is then closed by a threaded cap. The centre hole in this cap permits the striking end of the pin to come through to the front in certain positions of the block and to hit the primer. The rear end of the block is countersunk to receive the operating-lever, the locking-latch and its spring, the cocking-lever and its hinge-pin, the trunnioned collar, the notched cap, and the sear and its spring.

The extracting-device engages in front of the cartridge-head and grips it for more than one eighth of its circumference. Its motion is guided parallel to the axis of the piece by two cylindrical arms working in slots cut in the breech. Swinging the carrier-ring around its pivot causes the extracting-device first to act as a wedge to loosen the cartridge-case, and then by a rapid motion the case is thrown out of the gun, or far enough to the rear in the breech to be easily removed by hand.

The operation of the mechanism of the gun is as follows:

The operating-lever is seized with the left hand, and a handle on the right rear face of the carrier-ring with the right hand. The lever is pulled slightly more than 90° to the left.

The first motion of the lever unlocks the cocking-latch; the remainder of the motion rotates the block in the carrier-ring, disengaging the screw-threads. During this motion of rotation the cocking-lever has pulled back the firing-pin, which is held in position by an edge of the sear engaging under a notch on the screw-cap.

The carrier-ring is then swung to the left by the handle in the right hand.

The block moves to the left with the ring and passes partly through the slot out of the breech and uncovers the bore.

The first motion of the ring loosens the cartridge-case, as before described, and then ejects it. The new charge is then thrown in, no care being taken to seat it; the ring swung to, and the block rotated and locked.

As soon as the block is locked, pulling the sear fires the gun.

FIXED AMMUNITION.

Smokeless powder will be used, about 1¾ lbs. forming the charge.

The shell, cast iron, weighs 16 lbs. and also contains a bursting-charge of 8 oz. of powder.

The shrapnel will be similar to the Frankford Arsenal shrapnel now manufactured, but longer and heavier (16 lbs. 10 oz.), and will break into about 240 pieces (balls and fragments).

The metallic case, brass or aluminum, has the projectile inserted in it to the distance of 1.75 inches, the base of the projectile being separated from the powder-charge by a felt wad. The total length of a round is 18.33 inches.

Experiments with charges of Troisdorf powder from 1 lb. 8 oz. to 2 lbs. 1 oz. have given with the 3.2-inch gun velocities from 1765 to 2032 ft.-sec.

Supplying Ammunition.—It is proposed to have boxes that can be readily opened and closed containing a certain number of rounds, about ten for 3.2-inch gun, carried by the supply-train. When a battery requires ammunition, the boxes will be taken from the ammunition-wagon, opened and the chests filled. The empty metallic cases with the battery are then placed in the boxes, which are securely closed, loaded on the ammunition-wagon and returned to the depot by the officer in charge; and are from there returned by the ordnance officer to the Frankford Arsenal to be again filled and prepared for service. The cost of supplying ammunition by this method will be less than it is now.

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