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German 88-mm antiaircraft gun   ...........................................................		4
Breech mechanism   ..............................................................................		5
Firing mechanism   ................................................................................		6

4. GERMAN 88-MM ANTIAIRCRAFT GUN.

a. The German 88-mm antiaircraft gun consists of a detachable breech ring with a half-length outer tube, a half-length inner lock tube, and a loose three-piece liner.

b. The liner separates into three sections, one division being two-thirds of the rifled length back from the muzzle, and the other division being approximately 6 inches to the rear of the origin of rifling. Instead of replacing the entire length of liner as is the practice in this country, economy is achieved by replacing just that section of the liner which receives the most wear, i.e., the forcing cone section.

c. The front and center sections of the liner are keyed in place so as to aline the rifling and prevent relative rotation. This joint does not have any seal other than that provided by close tolerance machining. The center and rear sections are merely overlapped and not keyed in place as there is no rifling to aline (fig. 3).

Figure 3 — Center and Rear Sections of Liner

d. The three sections are alined end to end and then fitted into the inner tube (fig. 4). This tube serves to prevent lateral movement and to prevent rotation between the rear of chamber sections and other sections of the liner. The locking collar (fig. 4) prevents forward movement, and the locking ring (fig. 4) prevents movement to the rear. See figure 5 for method of fastening the chamber sections of liner to the inner tube. When the locking ring and collar are fully tightened, the liner sections are drawn up snugly and the joints offer little or no resistance to the passage of the projectile. The female threads in the locking collar are left-hand as indicated by the word "LINKSGEWINDE" (fig. 6). The collar is rotated in the direction of "LOOSE" ("LOS") for removing and in the direction of "TIGHT" ("FEST") for tightening.

Figure 4 — Tube and Liners

Figure 5 — Method of Securing Chamber Sections of Liner to Inner Tube

Figure 6 — Markings on Locking Collar

e. The inner tube which contains the liner sections is slipped into the outer tube (fig. 4). The latter tube has fastened to it the forward end of the slides. The breech ring also fits on the outer tube. The inner tube is secured by the locking collar (fig. 4) to prevent forward and rearward motion. See figure 7 for the method of securing the inner tube to the outer tube.

Figure 7 — Method of Securing Inner and Outer Tubes

f. The breech ring does not screw on the tube as is the practice in this country. Instead, the breech ring slides over the tube until it is seated and then the securing collar (fig. 4) draws it up tightly. This eliminates the need for rotating the tube or breech ring. In order to prevent rotation of the outer tube and the two locking collars, keys are provided. See figure 8 for installation of the keys.

Figure 8 — Method of Fastening Breech Ring to Outer Tube and Securing Collar

5. BREECH MECHANISM.

a. The breech mechanism is of the horizontal sliding breechblock type actuated by a breech operating spring permitting semiautomatic or manual operation (fig. 9). The breechblock slides in a rectangular breech ring which is bored to receive the outer tube and the breech block. Channels are machined into the bottom of the ring to permit installation of recoil slide pads. The recoil piston rod lug is made an integral part of the breech ring.

Figure 9 — Breech Mechanism

b. With the breech mechanism set for semiautomatic operation, a round of ammunition, when pushed in the breech recess of the gun, will trip the extractors and allow the breechblock to close under the action of the breech actuating spring. When the gun is fired, and recoils, the breechblock actuating shaft, which is operated by the breech operating crank, is rotated by the cam on the side of the cradle (fig. 10). This action winds up the lower breech opening spring and draws the intermediate plate away from its stop.

Figure 10 — Breech End — Right Side

c. When the breech operating crank is in the straight position of the cam path, the catch on the top spring cover disengages the lug retaining the breech actuating mechanism closed. Then the actuating shaft is free to rotate to the open position under the action of the breech opening spring, taking the crank with it and so opening the breechblock by the action of the breechblock actuating lever. The extractors are tripped and the empty case is ejected.

d. In the full open position, the compression of the breech opening spring is taken between the lug on the intermediate plate and its mating step. Any further opening motion of the breechblock is then taken up by the breech closing spring which, at this stage, acts as a breechblock buffer stop.

e. The breechblock is held open by the action of the extractors hooking on the recesses in the breechblock against the action of the upper spring which has been further wound up during recoil.

f. With the breech mechanism set for hand operation, the springs are disengaged from the breech actuating mechanism and the breech block may then be opened or closed with no spring influence.

g. The breechblock may be closed without loading a round by the action of the extractor actuating shaft. This is a splined shaft extending through both extractors. The extractors are tripped and removed from the recesses in the breechblock by rotating the shaft by hand (fig. 11).

Figure 11 — Extractors and Actuating Shaft

6. FIRING MECHANISM.

a. The firing mechanism is composed of the percussion mechanism, percussion mechanism release assembly, the cocking lever assembly, and the cradle firing mechanism.

b. The percussion mechanism is composed of the firing spring retainer, firing spring, firing pin, and firing pin holder (fig. 12). This group is held in the axial hole of the breechblock by a lug on the firing spring retainer engaging a mating groove in the breechblock. The percussion mechanism is operated through the percussion mechanism release assembly.

Figure 12 — Percussion Mechanism

c. The percussion mechanism release assembly is located in various recesses of the breechblock. This assembly is composed of the cocking arm, operating rod, operating rod spring, safety stop lever, operating rod guide, sear, sear spring, and sear operating lever. Through this assembly, the percussion mechanism is cocked either automatically or normally.

d. Cocking of the percussion mechanism automatically is accomplished during opening of the breech, with the cocking lever in the "FIRE" ("FEUER") position. As the breechblock slides to the right in recoil or hand operation, the cocking arm is engaged by the breechblock actuating lever. As the actuating lever rotates on the actuating shaft, the cocking arm is also rotated. The cocking lug on the firing pin holder is engaged and slid to the rear, compressing the firing spring. When the holder reaches the cocked position, the sear lug on the holder is engaged by the notch of the sear, which holds the mechanism cocked.

e. Manual cocking of the percussion mechanism is accomplished by the cocking lever (fig. 13). This lever is located on top of the breech ring. The breech must be closed when manual cocking is performed. The cocking lever serves the same purpose as the actuating lever, i.e., to rotate the cocking arm. However, in this case, if the cocking lever is kept in the rear, the firing mechanism will not operate but will be on "SAFE" ("SICHER") (fig. 13) because the lug on the cocking arm will not have cleared the lug on the firing pin holder. Thus the cocking lever also serves as a safety. The arc described by the cocking lever during manual cocking of the percussion mechanism is marked "WIEDERSPANNEN" which, freely translated, means "recock."

Figure 13 — Breech Mechanism — Top View

f. The cradle firing mechanism is located on the left side of the cradle. Raising the firing lever (fig. 14) of the cradle firing mechanism forces the lug up at the end of the sear operating lever. This, in turn, pushes the sear down against the sear spring disengaging the sear lug. The firing pin holder and firing pin, thus released, are driven forward by the compressed firing spring to fire the primer in the cartridge.

Figure 14 — Loading Tray Interlock Mechanism

g. The firing mechanism will not operate unless the breechblock is fully closed. If the breechblock is not fully closed, the operating rod will not be fully in position against the compression of the operating spring rod. This will prevent the safety stop lever from rotating, and hence will not permit clearance for the firing pin holder to move forward, thus rendering the firing mechanism inoperative.