[Lone Sentry: 3.7-cm Pak Antitank Gun; WWII German Infantry Weapons]
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German Infantry Weapons
Military Intelligence Service, Special Series No. 14, May 25, 1943
[DISCLAIMER: The following text is taken from a WWII U.S. War Department Special Series publication. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]


16.  3.7-CM PAK2

a. General

The 3.7-cm Pak (1.45-inch antitank gun) formerly the chief German antitank gun, has been largely replaced by the 5-cm Pak 38, but the 3.7-cm Pak is still likely to be encountered (see figs. 58 and 59). It has recently been provided with the AP 40 type of ammunition, which has a good penetration performance at ranges up to 400 yards. A stick bomb 5.7 inches in diameter and 11 inches long, with a rod which fits into the bore, has also recently been introduced (see fig. 62). Its use is likely to be restricted to short ranges. The bomb is the hollow-charge type. The gun is also in service with the Italian Army.

[Figure 58. 3.7-cm Pak.]
Figure 58.—3.7-cm Pak.

This gun, which is organic equipment of the German infantry regiment,3 is normally towed on its own wheels by a prime mover, but may also be carried in a truck. Weighing only about 880 pounds, it is a suitable weapon for use by airborne troops.

b. Table of Characteristics
Muzzle velocity:  
     AP   _ _ _ _ _ _ _    2,625 feet per second.
     AP 40   _ _ _ _ _ _ _    3,450 feet per second.
Effective range   _ _ _ _ _ _ _    600 yards.
Rate of fire   _ _ _ _ _ _ _    8 to 10 rounds per minute.
Length of gun   _ _ _ _ _ _ _    65.52 inches.
Elevation   _ _ _ _ _ _ _    25 degrees.
Depression   _ _ _ _ _ _ _    8 degrees.
Traverse   _ _ _ _ _ _ _    60 degrees (6 degrees with trails closed).

c. How to Operate

(1) Safety.—There are three safety arrangements:

(a) Before the breech can be opened after a misfire, the hand-operated block stop must be released by pressing the plunger (see fig. 59).

[Figure 59. 3.7-cm Pak in action.]
Figure 59.— 3.7-cm Pak in action.

(b) When turned to sicher ("safe"), the safety catch on the left prevents the sear from releasing the firing pin, and also prevents the breech from opening.

(c) The gun cannot be fired when the buffer cylinder is not correctly assembled, as a spring-loaded plunger prevents the actuation of the sear.

(2) To load and fire.—To open the breech, set the safety catch at Feuer ("fire"), press the hand-operated block-stop plunger (top left of the rear face of the breech ring) and turn the breech-mechanism lever clockwise (see figs. 60 and 61). The plunger is pressed back automatically by inertia when the gun is fired.

To load the gun, insert a round and give it a final impetus in order to cause the breech, to close automatically.

To fire the gun, press the push button in the center of the elevating handwheel. Firing may also be accomplished by pulling outward the trigger lever located on the right of the breech. The firing mechanism is recocked automatically during recoil.

To recock after a misfire, push the right-hand firing lever toward the piece, and start opening the breech until resistance is felt. The hand-operated block-stop plunger must not be pressed in, or the breech might open completely. The breechblock is automatically unlocked after firing, and the block stop goes forward by inertia. Movement of the breech-mechanism lever then extracts the cartridge case.

(3) To open trails.—With the trails closed, the traverse is only 106 mils (6 degrees), but with the trails open it is 1,062 mils (60 degrees). To open the trails, lift the locking lever at the trail end. Press down the locking levers of the trail hinges. Lock the trails in the open position by pushing up the hinge locking levers.

[Figure 60. Close-up of rear of 3.7-cm Pak.]
Figure 60.—Close-up of rear of 3.7-cm Pak.

(4) Sights.—The sights are mounted on an upright bracket carried on the top of the carriage. Adjustment of the sights is obtained by two pairs of adjusting screws (one pair for vertical adjustment, the other for horizontal).

(5) Gun crew.—The German gun crew numbers six, with duties as follows:

(a) The chief of section is responsible for seeing that all duties are properly performed, all commands executed, and all safety precautions observed.

(b) The gunner lays the piece.

(c) No. 1 loads and fires the piece.

(d) Nos. 2 and 3 handle the ammunition.

(e) No. 4 drives the prime mover.

[Figure 61. Breech mechanism of 3.7-cm Pak (viewed from top, rear).]
Figure 61.—Breech mechanism of 3.7-cm Pak (viewed from top, rear).

d. Ammunition

The following three types of ammunition (carried in 12-round metal containers) are fired:
 Type   Weight of 
 Weight of 
 Fuze   Marking 
AP tracer shell   3 lbs 2 oz   1 lb 8 oz   Base (Bd.Z. (5103))   Black shell marked 
    3.7-cm Pak Pzgr. 
AP 40 shot1   2 lbs   12.5 oz   None   Black shell marked 
    3.7-cm Pak Pzgr. 40.  
HE tracer shell   2 lbs 10 oz   1 lb 6 oz   Delayed action (either 
    A.Z. 39 Rh S274 or 
    Rh S222). 
 Gray shell marked 
    3.7-cm Spgr. 
1 This projectile consists of a mild steel body, an aluminum-alloy windshield (ballistic) cap, and
tungsten carbide armor-piercing core.

In addition to the ordinary types of ammunition listed above the Germans have developed a stick bomb for use with the 3.7-cm Pak (see fig. 62). The stick bomb consists of a hollow-charge projectile attached to a perforated sleeve within which there is a rod. The rod fits into the muzzle end of the bore; the concentric perforated sleeve fits over the muzzle end of the barrel. The standard 3.7-cm shell case and primer are used with a propellant charge of 216 grams of nitrocellulose. There are two fuzes, one in the nose and another in the base.

[Figure 62. Stick bomb for use with 3.7-cm Pak.]
Figure 62.—Stick bomb for use with 3.7-cm Pak.

e. Maintenance

(1) Stripping.—(a) To disassemble breech mechanism.—Press the hand-operated block stop, and open the breech all the way by pulling the breech-mechanism lever to the right rear. Insert an artillery tool between the shoulder of the plunger and the link of the breech-mechanism actuating shaft in order to take the weight off the spring. Remove the axis pin and the spring case by turning 40 degrees to the right. Release the extractors, slightly closing the block to remove the axis pin. Remove the extractors. Open the breech fully and remove the actuating spindle and the breech-mechanism lever. Remove the breech-block.

(b) Recoil.—The recoil cylinder is hydraulic, being filled from the center of the piston shaft at the rear by using a screw pump. The liquid is of the glycerine type. The cylinder contains 2 pints when full. To disconnect the gun from the recoil system, use a small flat bar to turn the connecting ring counterclockwise, about one-half turn. This presses back a safety plunger at the lower forward face of the breech ring and locks the firing mechanism.

If, during recoil, the recoil indicator on the right of the cradle reaches graduation 595, further firing is unsafe.

German handbooks recommend that no one shall stand within 35 feet directly in rear of the gun when it is being fired, as the piece may become separated from the cradle.

The recuperator is of the double-banked spring type.

(2) Assembly of breech mechanism.—Insert the hand-operated block-stop spring and retaining bush. Place the breechblock in the breech ring in the fully open position, insert the actuating shaft of the connecting arm into the breech ring, and connect the breech-mechanism lever. Insert the actuating spindle. Insert the extractors by slightly closing the breech to admit the extractor axis pin, and then close the breech. Next, insert the return spring and plunger, placing the flats of the plunger into a link of the breech- mechanism actuating spindle. Insert the axis pin as far as possible. Then release the hand-operated block stop and open the breech until it is held by the extractor claws, and press home the axis pin. Insert the firing pin and release the sear. Replace the main spring and cover plate, giving the cover plate a quarter turn, and release it.

f. Carriage

(1) Axle.—The axle incorporates an independent suspension, which is, however, locked when firing. The releasing and locking are controlled by the opening and closing of the trail legs.

(2) Lower carriage.—The lower carriage has a pivot housing and bearing face for the top carriage. It also houses the axle and carries the traversing rack, the traveling clamp, and the locking gear for the trail legs.

(3) Traversing mechanism.—The gunner is on the left side of the weapon and operates the traverse with his right hand by a small handwheel (clockwise to the right, counterclockwise to the left). (See fig. 63.) The traverse is 60 degrees (1,062 mils), and is completed by 30 1/2 turns of the handwheel.

(4) Elevating mechanism.—The arc of 21 degrees (372 mils) elevation and 13 degrees (229 mils) depression is completed by 33 1/2 turns of the handwheel, which the gunner operates with his left hand. (See fig. 63.)

(5) Cradle.—A locking device for use when traveling is mounted at the rear end and mates with the upper carriage when fully elevated. A leather buffer is fitted to the rear end and forms a stop for the gun on counterrecoil.

(6) Shield.—The shield is composed of the gun shield and the leg shield. The leg shield folds under the lower carriage when traveling, and folds down to the ground level when in action. The gun shield has a slope of approximately 45 degrees when in action, the upper half being hinged and folded forward as required.

[Figure 63. Carriage of 3.7-cm Pak, showing traversing and elevating mechanisms.]
Figure 63.—Carriage of 3.7-cm Pak, showing traversing and elevating mechanisms.

1 The information in this section is mainly based on reports; facilities have not been available to make an actual examination of the pieces. The German Army provides infantry howitzers and antitank guns as accompanying weapons of the infantry. These weapons are also equipment of German artillery units. For a description of their employment under desert conditions see "Artillery in the Desert," MIS Special Series, No. 6 (Nov. 25, 1942).
2 Pak is the German abbreviation for Panzerabwehrkanone which means "antitank gun." Pak has gained currency as a word. Note that the German practice is to designate artillery calibers in terms of centimeters rather than millimeters (see par. 21, p. 101, below). The German tactical symbol for 3.7-cm Pak is [3.7-cm Pak Symbol] or [3.7-cm Pak Symbol].
3 See fig. 1, p. xii, above.

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