Tag Archive for 'tapered bore'

7.5/5.5 cm Pak 41: Tapered Bore Antitank Gun

7.5/5.5 cm Pak 41: Tapered Bore Antitank Gun

The 7.5 cm Pak 41, Germany’s latest antitank gun to be brought into service, is designed on the Gerlich or tapered-bore principle. The bore tapers from 7.5 cm at the breech to 5.5 cm at the muzzle, but the taper is not constant. The first part of the bore is cylindrical and rifled; the second, conical and unrifled; and the third, measuring 27.6 inches in length, is cylindrical and unrifled. There is also a muzzle brake. The life of the barrel is estimated at approximately 500-600 rounds. The weapon is long, low, and sturdy in appearance and has a semi-automatic breech mechanism of the vertical wedge type.

The carriage has a split trail and is mounted on metal wheels with solid rubber tires. As traction is by motor tractor, the carriage is fitted with pneumatic brakes controlled by the driver of the tractor. Torsion bar suspension is automatically cut out when the trails are opened.

An elevating mechanism of the sector type is on the right-hand side of the cradle, and a traversing mechanism of the screw type on the left. There is no equilibrator mechanism. The recoil mechanism contains a hydraulic cylinder and spring-type recuperator.

The sighting system, which is graduated up to 1,500 meters (1,635 yards), has four scales for use according to the actual muzzle velocity of the gun. Muzzle velocity drops considerably because of wear.


Caliber           7.5/5.5 cm
Weight in action         1.4 tons
Length of barrel (approx.)         170 ins.
Muzzle velocity (estimated)         4,123 f/s
Elevation         -10° to 18°
Traverse         60°
Armor penetration—A.P.C.

       Range in yards          Thickness of armor in inches 
                   Normal               30°    
       500  6.67  5.75  
       1,000  5.94  5.12  
       1,500  5.28  4.49  
2,000  4.63  3.94  

German: p. 123

2.8/2.0 cm Pz. B. 41: Tapered Bore Antitank Gun

2.8/2.0 cm Pz. B. 41: Tapered Bore Antitank Gun

The German antitank gun, Pz. B. 41, captured in the vicinity of Halfaya Pass during the Libyan campaign in 1941, is the first tapered-bore weapon to be found in combat use. Served by a five-man crew, it is normally towed on a trailer, but can be broken down into five loads and transported on a truck or in an airplane.

The tube, which is of heavy monobloc or cold worked construction, is modeled on the Gerlich principle—that is, it is tapered from 28 mm at the breech to 20 mm at the muzzle in order to increase the velocity. No provision is made for cooling the barrel, which is good for about 400 rounds. The forward end of the tube has a muzzle brake threaded to it; the back is attached to the breech ring by an interrupted screw arrangement.

The firing mechanism, of the inertia type, consists of the firing-pin, firing-pin guide, spring and retainer. A breechblock of the horizontal sliding block type is actuated, after cocking, by an operating handle attached to the top of the breech ring.

Both the carriage and pedestal are of welded construction. Shields fixed to the carriage by metal hooks and spring plungers are constructed of steel plates about 3/8 inch thick. Detachable trunnions for fastening the gun and recoil mechanisms to the pedestal permit quick assembly and breakdown of the piece.

The wheels are of the perforated disk type and have pneumatic tires mounted on them. These tires, which are probably Lynthetic, have no valve stems, indicating that they are filled with a cushioning material.

The trails are of the split type and can be locked together or spread at an angle of about 45°.

The gun is flexible on its mount, and as no elevating or traversing gears are employed, these operations are most likely manual. A straight tube telescope is used.


Caliber            28 mm at breech
20 mm at muzzle
Weight (complete) 491 lb.
     (tube) 76 lb.
     (barrel & brake) 80 lb.
Length of barrel 61.36 ins.
Breech mechanism Horizontal sliding block
Firing mechanism Inertia type
Recoil mechanism Hydro-spring
Normal recoil 9.34 ins.
Rate of fire 8 to 10 rds./min.
Muzzle velocity 4,550 f/s
Range (effective) 500 yds.
Ammunition A.P. (9,754.4 grs.)

        Range       Thickness of armor in inches
Yards         30°         Normal
400       2.1       2.6

German: p. 131

4.2/2.8 cm Pak 41: Tapered Bore A.T. Gun

4.2/2.8 cm Pak 41: Tapered Bore A.T. Gun

The Pak 41 first appeared in the European Theater of Operations in 1942. It is the second of the German tapered-bore antitank guns. The monobloc barrel is long, with marked external as well as internal taper. There is no muzzle brake. The breechblock is of the horizontal sliding wedge type opening to the left. There is no provision for automatic opening; it is manually opened by means of the operating handle situated on top of the breech ring. The firing mechanism is a combination percussion inertia type.

The recoil mechanism of the hydro-spring constant type is similar in construction to the 3.7 cm Pak. It is housed in the cradle. The recoil cylinder moves with the barrel; the piston rod, secured to the front of the cradle, remains stationary. The buffer rod is centrally fixed to the rear of the recoil cylinder and slides in the hollow piston rod.

The elevation and traverse mechanisms are both fitted to the left side of the upper carriage.

The piece is mounted on the 3.7 Pak carriage fitted with sheet-metal, pneumatic-tired wheels, with tubular trails approximately 7 feet, 3 inches long. A light, steeply sloping, spaced armor shield is also provided.

A curved arm, riveted to the left side of the upper carriage, houses at its upper end the sight bracket trunnion from which the telescope carrier is hung.

Gerlich type ammunition, both H.E. and A.P., is used with the piece.


Caliber         42/28 mm
Weight 1,360 lb.
Rate of fire 10-12 rds./min.
Muzzle velocity 4,101 f/s
Weight of projectile (A.P.)* .80 lb.
Elevation 19°
Depression -14°
Traverse 44°

          30°         Normal
500 yds. 77 mm 94 mm
1,000 yds. 55 mm 68 mm
*This is a lightweight projectile consisting of a small tungsten carbide core embodied in a lightweight metal jacket. The jacket is so constructed that it is swaged to a smaller diameter as it moves through the tapered bore. This design permits a high muzzle velocity, but can be used for short ranges only as the velocity falls off rapidly. Penetration is accomplished by the core only, and because of its relatively small size very little damage is effected by it.

German: p. 128