The 47 mm Breda anti-tank gun is composed of the following parts: the barrel with the lock, the barrel's sleeve, the firing brake, the box of the firing brake with the swing, the upper carriage, the lower carriage, the sight devices.
The barrel is made of steel, with single walls, having a prism-shaped breech that contains the transversal chamber of the lock. In front of the breech, the barrel has two ribs for guiding the lock. Inside the rear side of the barrel there is a cone frustum-shaped room that holds the brass cartridge case and in the front there is the rifled part made of 24 grooves with constant turn. The barrel moves during the fire (recoils).
The lock performs the closing of the breech, the fire and the evacuation of the fired cartridge. The locking mechanism is a system with horizontal wedge (sliding in his chamber in the breech). The lock has inside the lugs of the percussion and fire mechanism, outside, on the lower part, the lug of the lever and counter-lever of the locking mechanism, and on the upper part two grooves for the guiding ribs on the upper part of the breech (in the lock's chamber). In the front part of the lock, on an inclined plane, there is the lug of the two extractors, and on the left part of the lock there is a hollow for loading the cartridge.
The locking mechanism is composed of a lever with a handle that crosses the breech in the right side and is linked of the counter-lever. The counter-lever has a prong that cocks the firing pin and connects with the cocking and uncocking nut.
The percussion mechanism is composed of a firing pin with an inner spring that leans against the closing plug. The firing pin has a rib against whose lower part leans the prong of the counter-lever, while the prong of the cocking and uncocking nut leans against its upper part, for manual re-cocking. In the opposing part of the rib, the body of the firing pin has a prong that leans against the cocking piston, when the firing pin is forward (uncocked) the inclined plane of the firing pin being in contact with the inclined plane of the cocking piston's prong. The cocking piston has a projection that props the spring, which leans in the opposite end against the closing plug, situated on the right side of the lock. The left extremity of the cocking piston has an inclined plane that comes in contact with the cocking nut.
Closing the breech, the action of the lever with handle in counter direction makes the prong of the counter-lever to leave the firing pin, which remains cocked in the prong of the cocking piston. To fire the gun, the firing lever must be pulled backward. During this action, the nut operates the cocking piston that sets free the firing pin, which under the action of the spring hits the percussion cap.
The firing mechanism is located on top of the breech and it is composed of the firing lever and the safety. The lever is connected to the cocking and safety fork that joins with the cocking and uncocking nut. The nut has a prong in its lower part, for manual re-cocking of the firing pin, with the breech closed. On the firing lever there is the safety that can fix the lever and prevent its action of the firing pin.
The extraction mechanism is a tube bound by the barrel with a locking lever and joined with the cylinder of the firing brake by a screwed part.
The sleeve of the barrel has on its both sides two recoil dampers that lean against two stiff arms of the upper carriage. On the right side there are the two recoil teeth (for the long recoil and the short recoil) that hits the recoil meter during the fire. The sleeve has on the lower side two claws that slides during the recoil on the two guiding grooves on top of the firing brake box. The sleeve has his axis converging forward with the axis of the swing, an important particularity because it helps increase the stability of the gun during the fire.
The firing brake is hydraulic, with recuperating springs. The cylinder of the brake is linked in the rear with the sleeve of the barrel and the piston's rod is linked in the front with the box of the brake. The recuperator is made of two springs inside the brake, in telescopic position (one inside the other). The braking fluid, weighting 1 kg, has the composition: 60% glycerine, 40% water, 20 gr Na2CO3. Before firing, the fluid lays in the forward part of cylinder, between the plug with fittings of the cylinder and the piston. During recoil, the movement of the cylinder together with the barrel and the sleeve, makes the fluid to flow in the rear part of the cylinder, throught two openings in the forward part of the piston's rod. The flowing space varies with a progressive shrinking of the two openings, so as the rate of flowing to decrease. In the same time with the flowing of the liquid from one side to another, the recuperating springs are compressed, opposing an increasing resistance until the recoil force is nullified. After the recoil stops, the two compressed springs loose, pushing forward the cylinder of the brake, while the fluid flows in the forward part of the cylinder.
The box of the firing brake is cylindrical and has on the upper side two guiding grooves on which the sleeve of the barrel is sliding. On the lower side it has the swing made of a toothed gear of the elevation mechanism. On the lateral sides it has two shoulders for binding with the upper carriage. Inside it has the firing brake.
The upper carriage is fork-shaped and has a cogwheel that mesh with the toothed gear of the swing. In the lower part it has a pivot that performs the centering and the linking with the lower carriage. The upper carriage has the two handles of the elevation and traverse mechanisms. In the upper part it has two stiff arms that prop the recoil dampers of the barrel's sleeve. The two arms are meant to allow the sleeve, pushed by the recuperating springs, to slide forward during the elevation motion so as to give the sleeve a supplement during the returning course, which grows progressively with the elevation.
The lower carriage is constituted of a platform supporting the pivot, to which the upper carriage is attached. It has two rear arms that links with the trails. On the upper part it has two guiding rails that come into their grooves on the upper carriage. The lower carriage has an axle with elastic suspension for the two wheels, and a helical teethed gear that is part of the traverse mechanism. The two trails are bound of the carriage by two locking levers that fix the trails in two positions: in the extension of the arms for firing, or for transportation, case in which the trails function as shafts. The two trails have spades for bracing the gun during fire.
|Vertical field of fire
|-10° to +60°
|Horizontal field of fire
|60°/ 46° over +12°
|Weight in action
|Weight in the march
|55.6mm at 100m
43.1mm at 500m
|6500 m with AP shell
4300 m with HE shell