RIFLED CANNON.
384. The rifled cannon at present in service are--
PARROTT.
-------------------------+-------+--------------------+---------+---------+
DENOMINATION. |WEIGHT.| CHARGE. | WEIGHT | WEIGHT |
| | | OF | OF |
| | | SHELL. | SHOT. |
-------------------------+-------+--------------------+---------+---------+
| lbs. | | | |
6.4-inch, or 100-pounder | 9,700 | 8 lbs. rifle. | 80 lbs. | 70 lbs. |
5.3-inch, or 60-pounder | 5,400 | 6 lbs. rifle. | 50 lbs. | 60 lbs. |
4.2-inch, or 30-pounder | 3,550 | 3-1/4 lbs. cannon. | 29 lbs. | 30 lbs. |
3.67-inch, or 20-pounder | 1,750 | 2 lbs. cannon. | 18 lbs. | 20 lbs. |
-------------------------+-------+--------------------+---------+---------+
DAHLGREN.
-------------------------+-------+----------------+---------+----------+
DENOMINATION. |WEIGHT.| CHARGE. | WEIGHT | CHARGE. |
| | | OF | |
| | | SHELL. | |
-------------------------+-------+----------------+---------+----------+
| lbs. | | | |
4-inch, or 20-pounder, | | | | |
bronze howitzer | 1,340 | 2 lbs. cannon. | 18 lbs. | 0.86 lb. |
3.4-inch, or 12-pounder, | | | | |
bronze howitzer | 880 | 1 lb. cannon. | 11 lbs. | 0.50 lb. |
-------------------------+-------+----------------+---------+----------+
385. CHARGES FOR PARROTT'S SHELL.
-----------------+----------+----------+----------+----------+---------+
| 8-INCH. | 100-PDR. | 60-PDR. | 30-PDR. | 20-PDR. |
-----------------+----------+----------+----------+----------+---------+
| lbs. oz. | lbs. oz. | lbs. oz. | lbs. oz. | lb. oz. |
Long | -- | -- | 3.4 | 1.8 | 1. |
Short | -- | 3.11 | 2.2 | -- | -- |
-----------------+----------+----------+----------+----------+---------+
386. SHELL AND SHOT GAUGES.
---------------------------+----------+----------+----------+----------+
| 100-PDR. | 60-PDR. | 80-PDR. | 20-PDR. |
---------------------------+----------+----------+----------+----------+
Greatest | 6.36 | 5.27 | 4.17 | 3.64 |
True diameter | 6.35 | 5.26 | 4.15 | 3.63 |
Least | 6.33 | 5.24 | 4.14 | 3.61 |
---------------------------+----------+----------+----------+----------+
387. In the rifle-guns of Mr. Parrott, provisionally adopted, it is
intended to retain the full charge of powder which a smooth-bore gun
of the same calibre would have with a round shot. The projectile for
the rifled gun is to be usually ten times the weight of this
charge.[41]
388. To obtain greater initial velocity, projectiles of less than the
full weight have been provided--solid shot of 70 pounds for the
100-pounder, with the front end "chilled." Such projectiles, though
not suited for long ranges, will be effective at 1,000 yards or less,
and are well calculated to act against oblique surfaces of iron.
389. The powder for the 100-pounder and 60-pounder should be of Rifle
(or, as formerly called, No. 7):--for the smaller calibres, 30-pounder
and 20-pounder, of Navy cannon powder. The cartridge-bags are the same
as those prescribed for similar calibres of smooth-bore guns.
390. The Parrott guns have been arranged for the use of a certain kind
of projectile, supplied by the inventor. These have reference not only
to the calibre and mode of rifling, but to the design of the gun
itself. For these reasons, the inventor objects to the use of any
other than his own form of projectile in the guns of his invention.
This request has been acceded to in the heavier calibres. The shells
of Schenkl and Hotchkiss have also been used, however, in the smaller
calibres.
It is not considered expedient to describe these projectiles, and it
is therefore directed that the Commander, Executive Officer, and
Gunner shall make themselves thoroughly acquainted with their
construction, and the percussion and time fuzes issued with them,
before sailing. The Ordnance Officer will furnish them with any
information on these subjects in his possession.
391. The projectiles consist of shells, shrapnel, and solid shot. All
rifled projectiles used in the Navy are of the expanding class; that
is, forced into the grooves by the action of the charge of powder, and
require no other precautions in loading than common spherical shells.
392. It is, however, essential--
1st. That the base of every rifle-projectile, especially the Parrott,
shall be thickly greased before entering it into the gun.[42] For this
purpose common pork slush, prepared by several washings in hot fresh
water, may be used.
2d. That the bores of all guns shall be frequently washed, the
grooves of rifled guns cleaned of all residuum and dirt, and a moist
sponge invariably used. After firing, the bore should be oiled with a
sponge.
The attention of Commanding Officers is especially called to this
requirement; and the Bureau desires that the action of Parrott's and
other rifle-projectiles fired under the above conditions, may be
carefully observed and reported; for it is believed that nearly all
the failures of projectiles in actual service result from the grooves
being filled, after a few rounds, with a hardened residuum of powder.
393. It is also necessary that the shell shall be close home on the
powder, otherwise the necessary expansion will not take place, and the
shell will tumble immediately after leaving the gun, utterly
destroying its range and accuracy.
394. In order to be certain that the projectile is properly home, the
rammer-handle must be marked to indicate it.
395. It is very important that dirt, sand, or other foreign substances
should not be carried into the gun on the sponge or the projectile, or
by the wind in batteries on shore.
In using guns on shore, a canvas muzzle-bag, a soft wad, or a light
stopper of wood, suggest themselves as means of security during the
interval between loading and firing the gun. The cover or stopper
might be removed, or left to be blown away at each discharge.
The longer the interval above alluded to, and the higher the elevation
at which the gun is kept, the more important and necessary are these
precautions.
396. Much care is taken to give the projectiles uniformity of size;
and if the powder is of suitable quality, those now supplied will
almost invariably take the grooves. Should difficulty in this respect,
however, be experienced, it may be remedied by separating the brass
ring from the iron at three or four points of the circumference. This
should be done with a cold chisel, very slightly, and so as not to
interfere with the loading. It is only necessary to sever the contact
of the two metals.
397. As the projectile slides in the gun with very little friction,
particularly when greased, the gun should therefore be elevated and
eased out when firing to leeward, that the shot may not be started
from its seat. An experiment to test this, showed that running a
100-pounder out with the force of its crew against the forward hurter,
the gun being level, started the shot forward nearly two feet.
Placing a grommet or other wad over elongated projectiles is
positively prohibited.
398. The 100-pounder and 60-pounder guns being, respectively, of the
calibres of the 32-pounder and 18-pounder spherical shot, and fired
with the same charges, these shot may be fired from them with
excellent effect, particularly on ricochet. The round shot should be
sewed up in canvas or felt, strapped to a sabot, or snaked between two
grommet-wads.
399. Both percussion and time fuzes are supplied for these rifle-guns.
When the object to be fired at presents a sufficient resistance, such
as masses of timber or earth, ships, or solidly-built houses, the
percussion-fuzes alone should be used from rifled cannon. They will,
however, frequently fail to explode the shell at long ranges, owing to
the shell not striking on its apex; or, if fired into loose earth,
which checks its momentum too slowly to make the plunger strike with
sufficient force.
400. It has been observed that time-fuzes burn with greater rapidity
in shell thrown from rifled cannon. Being in front, they are subjected
to greater pressure from the air. A similar effect is produced when
the fuze is confined under a water-cap, as in the naval time-fuze.
401. The fuze-holes of the heavy shells are cast larger than the
diameter of the regular fuze-stocks of the navy, which can, however,
be used with the aid of a bouching or an adapting ring, always sent
with the shells.
This bouching has heretofore been made of cast zinc. Others with a
flange and washer and the thread cut are now supplied, and the use of
the old rings is prohibited.
402. If it be desired to explode the shell in front of or in the midst
of a body of troops, or after having penetrated some resisting
obstacle, the time-fuze should be used. This is the only fuze to be
used with shrapnel.
403. The Vent is made in a bouching of pure copper screwed into the
gun. In the largest calibres the interior orifice is lined with
platinum.
The upper portion of the copper in naval guns is replaced by steel, to
obtain a harder surface for receiving the blow of the hammer. The
steel is three-fourths (3/4) of an inch thick.
A new vent can be readily put in, after getting out the old one,
without injury to the screw-thread. This can be done by boring out the
bouching with a drill, which leaves a thin shell containing the
thread. Into the hole thus made insert a square mandrel about four
inches, driving it lightly; by wrenching it, a portion of the shell of
the bouching can be detached and removed by unscrewing. This may be
repeated, and the whole of the old copper removed. The screw-thread is
then to be cleaned out, and the new vent-plug screwed in.
404. SIGHTS.--These consist of a fixed sight upon the right rimbase,
and a brass movable sight placed in a socket which is screwed into
the rear of the reinforce at the breech of the gun. The movable sight
is furnished with a sliding eye-piece, and is graduated up to 10 deg.. The
eye-piece is also capable of lateral adjustment to allow for the drift
as far as 10 deg., and for the effect of the wind. It is desirable that
the sights should be placed on both sides of the breech; otherwise, in
firing from a port at extreme train, there is a considerable loss of
lateral aim. Furthermore, with the sight on the right rimbase, it is
not convenient for the 2d Captain to attend the screw without
interfering with the aim.
405. These guns are all rifled to the right, by which it is understood
that the upper surface of the projectile is made to turn from left to
right, the observer looking from the breech towards the muzzle of the
gun.
406. DRIFT.--This is a deviation caused by the direction of the
rifling, is always to the right when uninfluenced by the wind, and is
to be allowed for.
407. The drift is in practice confounded with the deviation produced
by the direction and force of the wind, which may either annul or
increase it, according to whether it blows from right or left across
the line of fire. At long range it is also necessary to consider the
motion of the vessel across the line of fire. Suppose this to be at
the rate of six knots, and the gun is elevated 15 deg., the time of flight
would be by the Tables, 18 sec., while the deviation arising from this
cause would be upwards of 60 yards. It is therefore of great
importance that the Captain of the gun shall be carefully instructed
in making this adjustment of the eye-piece.
408. ELEVATING SCREW.--To obtain readily the changes of elevation
necessary in the use of rifled cannon, the heavier calibres are made
with very small preponderance, and are supplied with an elevating
screw which is attached to the carriage at the lower end, while the
nut is connected with the cascabel of the gun. Both screw and nut
admit of movements by which the screw can take any position required
in the various degrees of elevation. The parts should be allowed a
certain amount of play; if binding is prevented, it is believed that
the evident advantages of the screw may always be obtained.
409. RANGES AND TIME OF FLIGHT.--So far as ascertained, are contained
in Table VII., Appendix B.
410. PRECAUTIONS TO BE OBSERVED.--In the use of these rifled cannon,
it is of the utmost importance that all the directions relative to the
lubrication of the shell, its being close home, charge and kind of
powder used, and lining of the shells, shall be carefully observed.
Many premature explosions of shells having taken place in these guns,
which are attributed to various causes, such as,--defects of metal,
porosity, faulty fuzes, concussion and friction of the powder within
the shell,--it is ordered that, on the occurrence of a premature
explosion or rupture of a shell within the gun, it shall be
immediately washed out and a careful examination made of the interior
of the bore, by the mirror and by taking impressions in wax (_see_
Mode of Taking Impressions, p. 16, Part III.), and all the
circumstances of the case reported to the Bureau, specifying the kind
and calibre of the shells, kind of fuzes, the charge and kind of
powder, with its manufacturer's name: and,
Were the shells filled completely, and with what kind of powder?
Were the shells coated inside with any kind of composition?
Are any cracks or marks of scoring visible in the bores?
In rifled cannon, cracks or injuries produced by firing, or the
rupture of shells, are to be sought for--thus,
1. Around and in rear of the vent-bouching.
2. On the top of the bore, between the trunnions and
reinforce-band.
3. On the lower side of the bore, near the seat of the shot,
at the junction of the lands and grooves.
4. Near the inside of the muzzle, caused by explosion of
shells.
Although shells have been frequently ruptured in the guns without
leaving any visible traces of injury, yet they may be developed after
a certain number of rounds. Thus, in proving a gun at West Point, a
shell exploded in the gun at the second fire: on examination, no
traces of injury could be perceived; but, on a re-examination of the
gun after the tenth fire, a fine transverse crack was discovered in
the rear of the vent, extending two-thirds round the bore. It is
therefore important that frequent examinations shall be made, even if
no apparent injuries exist, as it is the opinion of the inventor of
the guns that the principal, if not the only cause of failure of these
guns in service, is due to the rupture of shells within the bore.
Experiments have been made, and are still in progress, which appear to
show that these premature explosions may be to a great extent
obviated, if not altogether prevented, by lining or coating the rough
surface of the interior of the shell with a smooth and elastic
coating.
All rifle-shells, except those for howitzers, before being issued for
service, shall therefore be lined or coated on the interior with a
mixture composed of--
16 ounces of soap--common yellow, not salt-water soap.
7 ounces of tallow.
7 ounces of rosin.
The tallow should be melted first, then melt and add the rosin, and,
lastly, the soap, bringing the mass to a heat that will make it _very_
fluid.
The shells having been first thoroughly cleaned, fill them about
one-third full of the composition, roll them slowly so as to spread
the mixture over the whole interior surface, and then pour off the
residue. This coating should be about five-hundredths (0.05) of an
inch in thickness, and is expected, from a series of experiments made
for the purpose, to prevent the premature explosion of shells in the
bores of rifled guns.
The Bureau further directs that hereafter the charge of the
100-pounder, or 6.4 inch, Parrott rifle, shall be reduced to eight (8)
pounds of rifle, or No. 7 powder, and that only the short shell or
solid shot, not exceeding eighty (80) pounds weight, and spherical
projectiles, prepared as directed in the Circulars of February 24th
and July 6th, 1864, be used in this gun.
411. EXTERIOR DIMENSIONS OF BOXES CONTAINING PARROTT'S PROJECTILES.
--------------------------------+---------+---------+---------
| LONG. | WIDE. | HIGH.
--------------------------------+---------+---------+---------
| Inches. | Inches. | Inches.
100-pounder, short 1 | 18-3/4 | 8-3/4 | 8-3/4
60-pounder, | | |
30-pounder, containing 10 | 25-1/4 | 11 | 15-3/4
20-pounder, containing 10 | 25-1/4 | 10-1/2 | 13
--------------------------------+---------+---------+---------
412. HOTCHKISS'S PROJECTILE FOR 20-POUNDER AND 12-POUNDER HOWITZER.
--------------------------------+---------+---------+---------
20-pounder, containing 5 | 24 | 12 | 6-1/2
12-pounder, containing 10 | 20 | 9 | 9
--------------------------------+---------+---------+---------
413. SCHENKL'S PROJECTILE FOR 20-POUNDER AND 12-POUNDER HOWITZER.
--------------------------------+---------+---------+---------
20-pounder, containing 5 | 24 | 14 | 7
12-pounder, containing 10 | 22-1/4 | 9-1/2 | 11-1/2
--------------------------------+---------+---------+---------
414. J.A.D. PROJECTILE FOR 20-POUNDER AND 12-POUNDER HOWITZER.
--------------------------------+---------+---------+---------
20-pounder, containing 3 | 15 | 12-1/4 | 7
12-pounder, containing 5 | 19 | 10-1/4 | 6
--------------------------------+---------+---------+---------
FOOTNOTES:
[41] Owing to the recent accidents which have taken place with these guns,
the 150-pounder has been withdrawn from service, and the charge of the
100-pounder provisionally reduced to eight (8) lbs. of Rifle powder, and
the short shell of eighty (80) lbs. only is to be used.
[42] The Schenkl, Hotchkiss, and some other projectiles, have a small
quantity of grease attached.