Chapter X: The 155-Mm Filloux Gun

WEIGHTS, DIMENSIONS, ETC.

Weight of Gun including breech
mechanism 8,795 lbs.
Length 232.87 inches.
Caliber 155-mm (6.1042 inches.)
Muzzle velocity 2,380 ft.-sec.
Rifling, one turn in 2.989. Caliber,
right hand uniform.
Weight of projectile 95 lbs.
Maximum range 16,200 meters.
Weight of maximum powder charge 25¼ lbs.
Weight of carriage 11,065 lbs.
Weight of gun and carriage, complete 19,860 lbs.
Diameter of wheels 1,160mm.
Width of track 2,250 mm.
Height of axis of gun 1,482 mm.
Elevation 0 to 35 degrees.
Maximum traverse 60 degrees.
Weight of limber complete 3,190 lbs.
Weight of gun carriage and limber 23,050 lbs.
The distance from center line of
carriage axle to center line of
limber axle, approximately 4,500 mm.

_The gun_ is of the built-up type and consists of the tube strengthened by the following jackets and hoops beginning at the breech end: The breech ring, the jacket, the hoop A, the hoop B, the clip hoop, the clip hoop set on the hoop B and the muzzle bell. The length of the gun from the muzzle to the breech base is approximately 18½ feet.

A recoil lug on the underside of the breech ring provides means of attaching the recoil and recuperator rods. Hinge lugs for the breech are also formed on the breech ring. Bronze clips to serve as guides in the cradle are screwed to the sides of the jackets.

_The breechblock_ is of the interrupted screw type, having four plain and four threaded sectors. The breech mechanism is of the plastic obturator type, having the forward mushroom-shaped head of the breechblock equipped with the asbestos ring, known as the obturator pad. Upon firing, this ring is compressed and acts as a gas check to prevent the leakage of powder gases back through the breech. It has sufficient resiliency to resume its original form after firing. The firing mechanism is of the French percussion primer type which is described under “155-mm Schneider howitzer” and is interchangeable with the guns enumerated therein.

_The cradle_ is a steel forging pivoted by trunnions in the trunnion bearings of the top carriage. It is bored with three parallel cylinders for housing the recoil and recuperator mechanism. On its upper side are slots for the gun slides and the elevating rack is bolted to the lower side.

_The recoil mechanism_ is of the hydro-pneumatic variable recoil type. The larger of the three cylindrical bores in the cradle block contains the recoil mechanism; the two smaller ones, the parts of the recuperator mechanism.

LONGITUDINAL SECTION IN BATTERY]

_The recoil mechanism_ consists of a piston and piston rod and a counter rod. The piston rod is connected to the breech lug and, therefore, recoils with the gun. Grooves of variable depth are milled along the length of the counter rod, controlling the flow of oil through the ports of the piston during the recoil. This counter rod assembles within the bore of the piston rod. It does not move longitudinally, but rotates. The amount of this rotation changes the area of the orifices through which the oil can pass. Its rotation is accomplished as the gun is elevated by means of an arm and gear sectors in such a manner as to shorten the recoil as the gun elevates.

A replenisher or gravity tank is provided in connection with the recoil cylinder which assures the recoil cylinder being full at all times and also takes care of any expansion of the oil due to heating. Its capacity is about 17 quarts.

_The recuperator mechanism_ consists of two connected cylinders, one containing the piston and piston rod which are attached to the breech lug, while the other contains a mushroom valve and a diaphragm. The diaphragm separates the oil contained in the first cylinder and part of the second cylinder from the high pressure air which compels the return of the gun into battery after recoil. Normally a small amount of oil must be between the valve and diaphragm. Oleonapth is the liquid used in this recoil mechanism. The amount of oil in the recoil and recuperator mechanism is shown by an indicator so that it can always be seen whether or not they need filling.

_The top carriage_ is a large steel casting mounted on the bottom carriage on which it pivots to traverse the piece.

The handwheels and mechanism for both elevating and traversing, are mounted on the top carriage. The tipping parts are carried on the trunnions of the top carriage.

Belleville Springs carry the weight of the gun when traversing, but on firing the springs compress and the firing stresses are taken on the bearing surfaces between the top and bottom carriages.

The bottom carriage is a large steel casting suspended from the axle (in traveling position) by a heavy multiple leaf spring. It supports the top carriage, houses the axle and provides hinge connections for the trail. When firing the axle is unshackled from the left spring and the bottom carriage bears directly on the axle.

_Traversing_ is accomplished by turning the top carriage which pivots on the bottom carriage. This is done by means of a rack and train of gears which are operated by the handwheel on the left side of the carriage. A traverse of 60 degrees, 30 degrees right and 30 degrees left, is possible.

_Elevating_ is accomplished by a rack on the cradle operated through gears by the handwheel located on the gear box at the left of the top carriage. Elevations from 0 degrees to 35 degrees can be obtained.

_The trail_ is of the split type and consists of steel plate beams of box section. Locks are pivoted at the forward end of the trails for securing them in the open position. When closed together they are clamped and attached to the limber. A traveling lock is provided on the trail for retaining the gun in retracted position.

Two types of spade are pivoted, one for soft and one for hard ground. When traveling the spades are always removed from the trail.

_The wheels_ are of cast steel, each wheel having two solid rubber tires.

Wheel shoes for traveling over soft ground are provided, which assemble over the rubber tires. They consist of twelve plates for each wheel which give a broad bearing surface under the wheel. The wheels are equipped with band brakes.

_The sighting equipment_ is exactly the same as that described with the 155-mm Schneider howitzer.

_The ammunition_ used is of the separate loading type. Either shrapnel or high explosive steel shell is used, as well as gas shells and other special ammunition. The projectile weighs 95 lbs. The propelling charge of smokeless powder is a sectionalized charge made up of two sections; a base charge and one smaller increment. The weight of the charge is 25 lbs.

The fuzes commonly used are the 31 sec. combination fuse for use with shrapnel and combining time and percussion elements: the point detonating fuse Mark IV used with the steel high explosive shell and the mark III point detonating fuze used with gas shell.