CHAPTER II. (2)

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3.2-inch Guns. Sights. Ammunition. Fuzes. Range Table.

3.2-INCH B. L. RIFLE, MODEL 1885 (MODIFIED). (Fig. 38.)

Material steel
Total length 7.56 feet
Calibre 3.2 inches
Weight 829 pounds
Grooves 24
Twist of rifling, uniform 1 turn in 30 calibres
Axis of trunnions above ground 3.56 feet
Powder-chamber ellipsoidal
Vent radial
Preponderance 50 pounds
Muzzle velocity 1685 ft.-sec.
Maximum range for shrapnel[4] 6613 yards

This gun consists of a tube (a), jacket (b), trunnion-ring (c), sleeve (d), key-ring (e), locking-ring (f), base-ring (g), and breech mechanism, De Bange obturator, vent-bushing of copper.

3.2-INCH B. L. RIFLE, MODEL '90. (Fig. 39.)

Material steel
Total length 7.31 feet
Calibre 3.2 inches
Weight 794 pounds
Grooves 24
Twist of rifling, increasing 1 turn in 50 to 1 turn in 25 calibres
Axis of trunnions above ground 3.56 feet
Powder-chamber cylindrical
Vent axial
Preponderance 31 lbs.
Muzzle velocity 1685 ft.-sec.
Maximum range for shrapnel 6613 yards
Distance between sights 30.7 inches

This gun consists of tube (g), jacket (h), and breech mechanism, De Bange obturator, vent-bushing of copper.

The jacket, trunnion-ring, base-ring, and sleeve, of the model of 1885, form one piece, and the key-ring is omitted, as the tube and jacket are locked firmly together by shoulders (a, b, c) in rear and shoulders in front, with a projection on the tube that fits into a corresponding recess in the jacket.

d is the powder-chamber, f the slope from no lands to maximum lands, and e the connecting slope for seat of rotary band.

The vent-cover is a pin working in a slot in the face of the carrier-ring. (See Fig. 36.)

SIGHTS.

Fig. 38.

Fig. 39.

Fig. 40.

The Front Sight (Fig. 40) is attached to the right rim-base, and consists of the base a, the standard b, and the cylinder c, all formed in one piece. The cylinder c is a bushing open at both ends, the interior being formed of two conical frustums c' joined at their smaller bases and having at this junction cross-wires (+), d, of platinum, which give the exact centre of the sight. In the new sights the cross-wires of watch-spring are placed diagonally (X). The cross-wires are used with the peep of the breech-sight, and the point e on top is used with the open sight.

Fig. 41.

The Breech-sight (Fig. 41) consists of a tangent scale affixed to a circular base revolving in a plane normal to the axis of the piece to compensate for inclination of trunnions when on uneven ground. The scale moves laterally on its base to correct for wind and drift, and bears a spirit-level, f. Along the vertical limb, C, of the sight, which is slotted, moves an eye-piece, D, actuated by a screw, d. This eye-piece (bearing the peep-sight d') extends on either side of the slot, the lower edge being horizontal and bevelled. The one on the right is graduated into ten equal parts. (The vertical limb being graduated into degrees (0 to 15°), and then sub-divided by diagonals into sixths, a diagonal scale of equal parts reading to minutes is obtained. The rear sights now being issued have range scales in yards for shell and shrapnel engraved upon the sight in addition to the degree scale. The scale of yards for shrapnel on the rear face of the sight, left side, is arranged with diagonal lines, to be read in the same manner as the degree scale. Each diagonal embraces 250 yards of range, and there are five divisions on the upper edge of the slide, by which this space is sub-divided, so that the intervals of 50 yards in range are read directly from the scale.

The scale of yards for shell, on the front face of the sight, is marked for each 100 yards of range, and is read from an index line on the slide.

The horizontal limb, or cross-bar, e, which is actuated by the screws e'e', is graduated into spaces, each of which corresponds to a deviation equal to 1/345 of the range. (In future constructions this division will correspond to 1/1000 of the range.) This variation is tabulated in the range table under the heading "Deflection for one division of the horizontal scale."

By means of a pivot, B, the sight proper is attached to the stem A, the axis of rotation being at the zero of the scale. The stem tapers so as to fit into the sight-socket fixed at the breech. A pin projecting from the stem, and fitting in a recess in the socket, insures the sight being properly placed on the gun.

The sight is first levelled and clamped by means of the clamp-screw a before sighting. Vertical and horizontal changes for elevation, drift, etc., are given by the thumb-screws d and e'e'.

THE POINTING ARC.

(Fig. 41a.)

This instrument, now under consideration for use with field-artillery, to replace wholly or in part the rear sight, is made principally of bronze, and comprises the arc a, the slide b, and the level-piece c.

The arc has two small seating plates, d d, secured to its base by countersunk screws.

The slide is connected to the arc by a dovetail-joint, and moves over it, the friction of a spring keeping the slide in any desired position. The tension of this spring is adjusted by the two screws on the side of the slide.

Fig. 41a.

The steel pin on the under surface of the slide moves in the groove on the upper surface of the arc, and, by abutting against the steel stop-pins e at each end of the groove, prevents the slide from being moved off the arc. The arc is graduated from 0 to 20 degrees, but readings to 2 minutes are obtained by means of the vernier, f, at the rear of the slide.

Plates, graduated in yards for shell or shrapnel, are on either side of the arc. They are removable, being graduated for the piece with which the arc is used.

The zero index-marks on the sides of the slide are supplemented by two others equidistant, plus 2 degrees and minus 2 degrees. Any one of the three may be used in setting the slide to a desired range in yards.

The top of the slide has a scale, graduated 3 degrees on either side of the zero, with sub-divisions of 6 minutes; the markings plus and minus are the reverse of those on the side of the slide. The vernier, g, on the level-piece permits of a least reading of 2 minutes being obtained. Motion is given the level-piece by the deflection-screw h.

To set the pointing arc, make the zero of the level-piece coincide with the zero of the slide-scale, and then take the required elevation in yards on the side desired. Should the piece and object fired at be on different levels, and the angle known, the index of the level is moved to indicate this angle—to the plus side if an elevation, and to the minus side if a depression; then take the elevation in yards as before.

The correction is made in this way for 3 degrees or less, but for angles above 3, up to 5 degrees, the 2-degree marks on the side of the slide must be used, the index mark of the level being moved to coincide with the mark corresponding to the number of degrees—elevation or depression—less 2 degrees. The plus 2-degree mark is used as an index when the object has an elevation, and the minus 2-degree mark when a depression.

To obtain the angle corresponding to difference of level, sight the piece on the object by the ordinary sight, using any elevation; set the pointing arc at this elevation, and move the level-piece by the deflecting-screw until the air-bubble is centred. The index of the level-piece then points to the desired angle—plus if an elevation, and minus if a depression.

If the wheels of the carriage be not on the same level the gun will shoot towards the lower wheel. A correction for this is made by a deflection-scale.

The correction for deflection due to inclination of trunnions, expressed in units of the deflection-scale, is, at any range, equal to the product of the angle of elevation and the angle of inclination of the trunnions, both expressed in degrees, into a constant multiplier. When the divisions of the deflection scale are 1/500 of the distance between the sights this multiplier is 0.1523; when the divisions are 1/1000 it is 0.3046. The rear sight must be moved towards the higher wheel.

Ammunition for 3.2-inch Gun.

The ordinary friction-primer is used for radial vents; for axial vents an attachment is made to the friction-primer of a thin brass wire about 18 inches long, looped or coiled for convenience, and having one end fastened in the loop of the friction-wire, and the other around the head of the body of the friction-primer.

The cartridge-bag is used, but experiments are now being made with metallic cases. (This proposed metallic ammunition for 3.2-inch guns comprises a projectile weighing 16½ pounds, with a suitable charge of smokeless powder to give an initial velocity of 1450 ft.-sec.)

Charge of powder 3¾ pounds I. K.
3½" sphero-hex.
Weight of projectile filled 13½"
Bursting-charge of shell 7 ounces
Bursting-charge of shrapnel 3"

Shell, shrapnel, and canister are used.

Shell.—The base-percussion-fuze shell (Fig. 42) is made of cast iron in one piece, having a band of soft brass or copper forced into a recess on the outside, ? of an inch from the base. The body and half of the head are painted black; the half of the head nearest the point is painted vermilion.

Canister.—The canister (Fig. 43) consists of a hollow cylinder of malleable iron, with one end closed by a cast head. The case is filled with from 222 to 226 balls, and a metal cover is inserted. Around the case are several slits, their ends overlapping to secure the thorough breaking up of the case on discharge.

Fig. 42.

Fig. 43.

There are several small holes in the head, through which a portion of the gas of the exploded powder-charge enters, drives forward the balls, and assists in disrupting the case.

Total weight of a round, 11 lbs. 10 oz.

This projectile is painted black.

Fig. 44.

Shrapnel.—The Frankford Arsenal shrapnel (Fig. 44) weighs 1310/16 lbs. Exclusive of filling it consists of three parts, viz., head (d), body (a), and base (b). The head is made of cast iron, bored and threaded to receive the fuze, and contains a powder-chamber which is lacquered to prevent danger of premature ignition by friction. The body is made of lap-welded wrought-iron or low-steel tubing, and is weakened for fracture by circular and longitudinal grooves on the inside. It contains 162 hardened lead balls, ½ inch in diameter, which are assembled in circular layers and held in position by cast-iron separators, which increase the effect of explosion by furnishing additional fragments. The base is made of cast iron threaded to screw into the cylindrical case, and is so formed as to provide a support for the copper band to prevent deformation of the case at this point from shock of discharge, c is the rotating band. This projectile is painted, body black, head vermilion.

Total weight, ready for firing 13 lbs. 10 oz.
Total number of balls and individual pieces 201
Bursting-charge 3 ounces

SHRAPNEL MADE BY AMERICAN PROJECTILE CO.

(Fig. 45.)

Fig. 45.

The entire case is of wrought steel electrically welded together so as to form a complete hardened wrought-steel case without joint. The powder-chamber is formed in the base by a hard wrought-steel diaphragm (d) supported by a cast-iron spider, and connected through the centre of the shell (axially) to the fuze-opening by a cast-iron tube. It is smooth-finished, and either tinned or lacquered. The shell contains 170 bullets (34 to the pound) packed in circular layers, and they are held firmly in position by a resin matrix. The bullets are introduced through a hole at c.

The exterior is painted as follows: body from the band forward, to include three fifths of head, black; remaining part of head, and part of body in rear of band, vermilion. The band is of copper.

Total weight of projectile complete 13½ pounds
Total number of balls and individual pieces 228
Weight of bursting-charge 3 ounces

The Frankford Arsenal combination fuze is used. This fuze weighs 17½ ounces; but if made of aluminum it will weigh only 7¾ oz. For field-artillery guns it is graduated from 1 to 15 seconds, the graduations being based upon the time of burning in flight. Each entire second is marked by a through-hole in the cone-cover, and each of these spaces is sub-divided into six equal spaces by holes nearly through the cover, which for the 3.2-inch gun will correspond to the following distances, viz.: 70 yards at 1000 yards range; 55 yards at 2000 yards range; 48 yards at 3000 yards range; 42 yards at 4000 yards range.

The following table gives the mean of five shots in each group:

Seconds. Range.
2 883 yards
3 1401"
5 1966"
6 2433"
8 3037"
9 3461"
12 4225"

The Frankford Arsenal Combination Fuze, 15 Seconds, Model 1894, for Shrapnel of Field-guns.

This is a time and percussion fuze (Fig. 46). It weighs 17½ oz. The time element is contained in the front part of the bronze body (a) of the fuze, and the percussion element in the rear part. The time-plunger (b) has five lugs (k) which hold the plunger in position above the firmly fixed steel firing-pin (c) after the safety-pin has been withdrawn; these lugs are broken by the shock of discharge. The safety-pin (j) passes through a hole in the upper part of the plunger, and it and the lugs are protected by the brass cap which is pierced to allow the insertion of the safety-pin.

Fig. 46.

By this arrangement the plunger and its lugs are entirely protected from any blow that may be received on the nose of the fuze. The priming composition is contained in the base of the plunger (at i), and is protected by a disk of tinfoil.

The compressed powder-ring (q) is held in a groove in the body of the fuze by a brass ring, and four holes (p) permit the flame from the composition (i) to ignite it.

The cone (d), made of an alloy, is held in place by a brass clamping-nut (h) and two brass pins (l). A lip (m) on the base of the cone fits into a corresponding groove in the fuze-body and prevents the premature ignition of the powder (o) in the fuze-chamber.

A groove in the cone contains the time-train (e), which communicates through a brass tube (n) with the powder in the fuze-chamber (o).

The brass cone-cover (f) is pierced with holes numbered from 1 to 15. The holes lie immediately over the time-train and correspond to seconds of graduation. The spaces between consecutive holes are sub-divided into six parts, and countersunk at the points of division so that the fuze may be cut to sixths of a second of burning.

A brass pin projects from the body of the fuze and fits into a slot in the cone-cover; it fixes the latter in position and, together with the brass cup on top, also serves to hold the cover in place.

The flame from the powder in the fuze-chamber communicates with the bursting-charge of the shell through the grooved surfaces of the primer, plunger-sleeve, and bottom closing-screw.

The opening into the fuze-chamber through which the charge is put is closed by the screw. A conical hole in the fuze-body immediately opposite this screw permits the insertion of a steel pin for the purpose of screwing the fuze into the shell.

The percussion element consists of a brass primer (t) having three vents through which the flame may pass from the composition to the powder in the fuze-chamber.

On the side towards the firing-pin the composition is covered first with a tinfoil cup and then with a copper restraining-disk, which is separated from it .04 of an inch both for safety and to prevent the firing-pin pressing against the composition during flight. On its opposite side the primer is covered with a tinfoil ring and a paper disk.

The bottom of the fuze is covered first by a paper and then by a tinfoil disk.

The primer, plunger-sleeve, and bottom closing-screw have their sides grooved longitudinally (r, r, r) to allow the flame from the powder in the fuze-chamber to pass to the bursting-charge of the projectile. With the exception of this difference in the plunger-sleeve the plunger is the same as the one in the Frankford Arsenal base percussion-fuze "C," model 1894.

TO USE THE TIME-FUZE.

Pierce the time-train cone at right angles to the axis and through the division in the cover corresponding to the desired number of seconds. Then remove the safety-pin before inserting the projectile in the bore of the piece.

A fuze-cutter is issued by the Ordnance Department for use with the fuze.

The Frankford Arsenal Base Percussion-fuze "C," Model 1894, for Field-gun Shell.

Fig. 47.

Fig. 48.

This fuze weighs 4.88 ounces and consists of a brass body (a) which contains the complete plunger. The head of the body is closed by a brass cap-screw (b) which contains a brass primer (d) that is filled with the composition (m); and the cap-screw is closed by a brass closing-screw (c). c and d have holes through them, as indicated, for the passage of the flame from the primer to the bursting-charge of the projectile. The head is covered by disks of paper and tinfoil.

The face of the composition (m) nearest the plunger is covered by a disk of tinfoil (e) and a copper restraining-disk (f).

The Plunger consists of a steel firing-pin (i), firmly fixed in a brass igniter plunger-spindle (h), and this spindle fits in a brass igniter plunger-sleeve (g) which has a groove (t') on its lower interior surface. A split brass safety-ring (i), which holds the igniter plunger-sleeve in the safety position, is slipped over the lower end of the spindle, and then the spindle-sleeve, containing two grooves (s and t), is slipped on and firmly secured by spreading the lower end of the spindle.

The inclination of the groove (s) determines the resistance of the safety-ring, which, in this fuze, has the minimum and maximum limits of 142 and 160 lbs. respectively. (It was formerly 15 lbs.)

When the piece is discharged the plunger-sleeve overcomes the resistance of the safety-ring and carries it to the rear; the diameter of the ring is slightly increased during its passage along the spindle, and when in the proper position for so doing it fits partly in both grooves (t and t'), binding sleeve and spindle firmly together. The point of the firing-pin now projects beyond the plunger-sleeve and the fuze is armed. When the projectile strikes, the complete plunger is thrown forward, the point of the firing-pin pierces the restraining-disk and ignites the composition.

Fig. 47 shows the position of the parts before the piece is discharged, and Fig. 48 during the flight of the projectile.

RANGE TABLE FOR 3.2 INCH B. L. RIFLE.

  • Shrapnel, 13.5 pounds
  • Muzzle velocity, 1685 ft.-sec
Range. Sight Elevation. Variations. Time of
Flight.
Fuze Scale. Change
in Height
of Burst,
1 minute
elevation
Fall. Terminal
Velocity.
Angle. Differs
from
Shell.
Range,
1 minute
elevation.
Deflection,
1 division
hor. scale.
Divisions at
which to cut
time-fuze.[5]
Variation
in range.
1 subdiv.
Angle. Inclination,
1 yard in--
yards. deg. min. min. yards. feet. seconds. units. sixths. yards. feet. deg. min. yards. f. s.
500 0 13 1 14 4.4 .97 0 4 80 .4 0 37 93 1426
600 0 20 1 13 5.2 1.18 1 0 78 0 46 75 1380
700 0 27 1 12 6.1 1.40 1 1 75 0 56 61 1335
800 0 35 1 12 7.0 1.63 1 3 73 1 6 52 1292
900 0 43 1 12 7.8 1.87 1 4 71 1 19 44 1251
1000 0 52 1 11 8.7 2.11 2 0 67 .9 1 32 37 1212
1100 1 2 2 11 9.6 2.36 2 1 67 1 45 33 1176
1200 1 12 3 11 10.4 2.62 2 3 67 2 1 28.5 1142
1300 1 22 3 10 11.3 2.89 2 5 62 2 17 25 1110
1400 1 33 5 10 12.2 3.16 3 0 62 2 34 22.5 1082
1500 1 44 6 9 13.0 3.44 3 2 58 1.3 2 52 20 1056
1600 1 55 6 9 13.9 3.73 3 4 58 3 11 18 1034
1700 2 7 7 9 14.8 4.02 3 5 58 3 30 16.5 1014
1800 2 19 8 8 15.7 4.32 4 1 55 3 50 15 995
1900 2 32 9 8 16.5 4.62 4 3 55 4 12 13.5 978
2000 2 45 10 7 17.4 4.93 4 5 52 1.7 4 34 12.5 962
2100 2 59 11 7 18.3 5.25 5 1 52 4 57 11.5 946
2200 3 13 11 7 19.1 5.57 5 2 52 5 21 10.5 920
2300 3 28 12 7 20.0 5.90 5 4 50 5 45 10 915
2400 3 43 13 7 20.9 6.23 6 0 50 6 11 9 901
2500 3 58 14 6 21.7 6.56 6 2 49 2.2 6 38 8.5 887
2600 4 14 16 6 22.6 6.90 6 4 49 7 5 8 874
2700 4 29 17 6 23.5 7.24 7 0 49 7 34 7.5 862
2800 4 44 17 6 24.4 7.58 7 2 49 8 4 7 850
2900 5 1 19 6 25.2 7.92 7 4 49 8 35 6.5 839
3000 5 18 20 6 26.1 8.26 8 1 48 2.6 9 7 6 829
3100 5 35 21 6 27.0 8.61 8 3 48 9 39 6 819
3200 5 52 22 6 27.8 8.96 8 5 48 10 12 5.5 810
3300 6 9 23 5 28.7 9.32 9 1 47 10 46 5.5 801
3400 6 28 25 5 29.6 9.68 9 3 47 11 21 5 792
3500 6 47 26 5 30.5 10.04 9 5 45 3.0 11 56 4.5 783
3600 7 6 27 5 31.3 10.41 10 1 45 12 32 4.5 775
3700 7 25 28 5 32.2 10.78 10 4 45 13 9 4.5 767
3800 7 45 30 5 33.1 11.16 11 0 44 13 48 4 759
3900 8 5 32 5 33.9 11.54 11 2 44 14 28 4 751
4000 8 25 33 5 34.8 11.92 11 5 44 3.5 15 8 3.5 744
4100 8 44 33 5 35.7 12.30 12 1 44 15 49 3.5 737
4200 9 3 33 5 36.5 12.68 12 3 44 16 31 3.5 730
4300 9 24 34 5 37.4 13.06 12 5 43 17 14 3 723
4400 9 44 34 5 38.3 13.45 13 2 43 17 58 3 717
4500 10 5 34 5 39.2 13.84 18 4 43 3.9 18 43 3 711

RANGE TABLE FOR 3.2-INCH B. L. RIFLE.

  • Shell, 13.5 pounds
  • Jump: 20' at 1°. 30' at 10°
  • Muzzle velocity, 1685 ft.-sec
Range. Site Elevation Variations. Time of
Flight.
Fall. Terminal
Velocity.
Range,
1 minute
elevation.
Deflection,
1 division
hor. scale.
Angle. Inclination
1 yard in--
yards. degrees. minutes. yards. feet. seconds. deg. min. yards. f. s.
500 0 12 14 4.4 0.96 0 36 95 1450
600 0 19 13 5.2 1.17 0 45 76 1408
700 0 26 12 6.1 1.39 0 54 64 1366
800 0 34 12 7.0 1.61 1 5 53 1326
900 0 42 12 7.8 1.84 1 16 45 1287
1000 0 51 11 8.7 2.07 1 28 39 1250
1100 1 -- 11 9.6 2.32 1 41 34 1215
1200 1 9 11 10.4 2.57 1 55 30 1182
1300 1 18 10 11.3 2.82 2 9 27 1151
1400 1 28 10 12.2 3.09 2 25 24 1121
1500 1 38 10 13.0 3.36 2 41 21 1094
1600 1 49 10 13.9 3.64 2 59 19 1070
1700 2 -- 9 14.8 3.92 3 17 17 1048
1800 2 11 9 15.7 4.21 3 36 16 1029
1900 2 23 9 16.5 4.50 3 56 15 1011
2000 2 35 8 17.4 4.80 4 17 13 994
2100 2 48 8 18.3 5.10 4 38 12 979
2200 3 2 8 19.1 5.41 5 -- 11 964
2300 3 16 7 20.0 5.72 5 23 11 949
2400 3 30 7 20.9 6.04 5 47 10 935
2500 3 44 7 21.7 6.36 6 11 9 923
2600 3 58 7 22.6 6.69 6 37 9 912
2700 4 12 7 23.5 7.02 7 3 8 901
2800 4 27 7 24.4 7.35 7 30 8 891
2900 4 42 7 25.2 7.68 7 58 7 881
3000 4 58 6 26.1 8.01 8 27 7 871
3100 5 14 6 27.0 8.35 8 56 6 861
3200 5 30 6 27.8 8.69 9 26 6 851
3300 5 46 6 28.7 9.03 9 57 6 841
3400 6 3 6 29.6 9.37 10 29 5 832
3500 6 21 6 30.5 9.71 11 1 5 823
3600 6 39 6 31.3 10.06 11 34 5 814
3700 6 57 6 32.2 10.41 12 8 5 806
3800 7 15 5 33.1 10.77 12 43 4 798
3900 7 33 5 33.9 11.13 13 18 4 790
4000 7 52 5 34.8 11.50 13 54 4 782
4100 8 11 5 35.7 11.87 14 31 4 774
4200 8 30 5 36.5 12.25 15 9 4 766
4300 8 50 5 37.4 12.63 15 47 4 758
4400 9 10 5 38.3 13.02 16 26 3 750
4500 9 31 5 39.2 13.42 17 5 3 743

                                                                                                                                                                                                                                                                                                           

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