The following information on the Mauser M712 full automatic pistol comes from Chapter 31 of Mauser Rifles and Pistols by W. H. B. Smith. Mauser Rifles and Pistols is also available to purchase in print.
This arm (known in Germany as the “Schnell-Feuer-Pistole”) is a full and semi-automatic weapon which is not strictly a pistol. It is more directly classifiable as a submachine gun.
It should be emphasized that its unlicensed ownership in the U.S. is a criminal offense, punishable under Federal Law. It must be registered with the Federal Authorities.
This arm is a modification of the original Military Model 7.63mm Mauser, and partakes of most of its general characteristics.
It was manufactured with a 10-shot box type magazine flush with the magazine housing (the bottom of the trigger guard) and also with a 20 shot magazine. Both are detachable.
When loaded through the top with a 10-shot clip, it loads in practically standard Mauser pistol fashion. However, it may also be loaded by inserting a loaded magazine from below. The breechblock must then be pulled back and allowed to move forward to chamber a cartridge. (When this arm is loaded from a clip through the top of the open action, the breechblock moves forward to chamber a cartridge when the clip is removed and the breechblock released from its rear open position.)
When loading this model, pulling the breechblock back cocks the hammer, which then rises into a cut in the underside of the breechblock to hold it open. Drawing back the hammer slightly with the thumb will ease it out of its notch in the underside of the breechblock to release that member. (Note that this differs from the original pistol in which removal of the clip alone releases the breechblock).
When the last cartridge has been fired, the breechblock is held back by a projecting stud on the carrier which leaves the pistol ready to receive a new magazine and also warns that the arm is empty.
In loading these later models, when the action is open, two successive clips of 10 cartridges each may be stripped down from above through the open action.
In unloading this weapon, the magazine should first be withdrawn, and then the breechblock pulled to the rear sharply to eject the cartridge from the chamber.
Note that this arm differs from the standard Military Model pistol in having a magazine release stud provided on the right side of the receiver. (The true pistol has a fixed instead of a detachable box magazine.)
This model follows all the general characteristics of the original military pistol in avoiding the use of pins and screws to retain working parts. The working elements are grouped in self-contained assemblies which operate largely through interlocking and through cam surfaces. All the mechanism is inserted from the rear into the receiver forging which consists of the grip section, the side plates, triggerguard and magazine housing, and supporting surfaces for the barrel extension.
The barrel extension is an integral part of the barrel forging itself. The breechblock assembly is mounted in the rear of the barrel extension in standard Mauser practice.
A new type of universal safety lock is provided which permits the safety to be applied when the hammer is up or down. When the safety is applied with the hammer up, the hammer may be lowered without danger since it cannot hit the firing pin.
Except for such differences in mechanism as are necessary to provide an automatic sear to enable full automatic fire, and the arrangement for detachable magazine insertion, the construction and design, while differing in weights of parts from the earlier semi-automatic military pistol, is identical with that earlier form.
M712 Fire Selection
On the left side of the receiver to the rear of the trigger is an oval plate. A spring button with a knurled head forms the center of this plate. When forward, the plate points to the letter “N” indicating “Normal”—that is, standard semi-automatic fire in which one pull of the trigger fires a cartridge, ejects the empty and reloads ready for the next trigger pull.
When the plate is pushed to the rear it points to “R”, indicating “Rapid”—that is, automatic fire as long as the trigger is held back.
This plate bears an integral pin passing across the inside of the receiver below the lockwork which has a bearing in the receiver.
Two cams are milled into this transverse plate pin, a large one near the center which engages with a spring-loaded lever which is pivoted to the trigger; and a smaller one on the right which is rounded to fit into a fork in an automatic sear disconnecting unit on the bottom of the receiver near the right hand sidewall.
Unlike the trigger in the standard type, this full automatic model trigger does not have a nose. A short spring lever bearing against the flat center cam on the transverse pin, is pinned directly to the trigger and is held against the cam by its spring. Since this lever is pivoted to the trigger below the trigger pivot line in the receiver, it provides long leverage.
While the loading, firing, locking and unlocking, extraction and ejection systems are about the same in both weapons, the action of the semi- and full automatic control requires attention.
M712 Semi-Automatic Action
When the sliding plate on the left side of the receiver is pushed forward to “N”, its pin inside the receiver brings the flat surface of its center cam to the trigger lever. Thus as the trigger is pulled it raises the sear lever and then slips forward out of it. This permits the sear to reengage in its bent in the tumbler as the hammer is driven back by the recoiling action after falling and firing the cartridge in the chamber. The action is substantially that of the standard Mauser Military Model pistol at this time.
M712 Full Automatic Action
In full automatic action, the side plate is pushed back to point “R”. In this position the pin inside is turned so that its cam faces the trigger lever, thereby advancing the trigger lever about .25 inch to the front. This changes the angle of trigger nose to sear lever; hence when the trigger is pulled, while the sear lever is elevated somewhat it still cannot slip off the nose of the trigger lever. Thus as long as finger pressure is maintained, the sear cannot engage with the hammer bent to hold the hammer back, and the arm will continue to fire as long as there are cartridges in the magazine.
While in some Spanish imitations of his pistol, the hammer follows the breechblock down to fire, this is not a good sear design. In the genuine Mauser a secondary sear is provided to make sure that the arm is completely locked before the firing of each round.
This secondary sear automatically holds the hammer back until the breechblock is fully locked, at which time it automatically releases.
It is positioned below and to the rear of the hammer pivot nearly opposite the primary sear. Like the primary sear, it has a broad bearing surface, reaching the entire width of the tumbler.
The secondary sear is a single unit having a wide bearing in each wall of the receiver. Its right side is shaped as a flat lever having unequal arms which position in recesses in the receiver, and it is flush with the primary sear spring and its lever. The lower arm is the shorter one. It engages with the disconnector bar. The long upper arm curves to the front where it ends in a rounded open hook projecting above the receiver into a slot in the underside of the barrel extension. This arm can move only within the limit provided by its recess. It is operated by a small coil spring and plunger mounted in a tunnel in the side of the receiver below the primary sear spring.
When the sear is in its notch, this upper arm projects above the level of the lock frame or receiver, and a forward movement will bring it below this lever. Thus as the breechblock travels to the rear and rolls over the hammer, the main bent is first caught by the primary sear and then by the secondary sear in its bent. As the secondary bent is cut further in the tumbler than the primary one, when the arm is firing full automatic, the hammer fall is somewhat longer as it is released by automatic or secondary sear action.
When the plate is set for full automatic fire, pressure on the trigger results in the primary sear being kept out of its bent as the hammer falls. As the breechblock during rearward movement unlocks from the receiver when the barrel is halted, the hammer tumbler after passing over the primary sear engages the secondary (automatic) sear momentarily.
Since the barrel extension is in full recoil at this point, the upper arm of the secondary sear thrust by its spring, rises up into its cut in the underside of the extension. The bent cannot engage until this point is reached.
The compressed recoil spring now reasserts itself and drives the breechblock forward to strip the top cartridge from the magazine and drive it toward the chamber. During the closing movement, the barrel extension begins this forward movement as the mainspring acts upon it through the rocker and the bolt lock. Thus the rear end of the slot in the underside of the barrel extension pushes the upper arm of the automatic or secondary sear, thereby releasing it from its bent, and permits the hammer to continue forward to hit the firing pin and fire the cartridge when the breech is fully locked.
The automatic disconnector during full automatic fire is unusual. There is a bar which can move in a groove in the bottom of the receiver. Its front connects with the transverse pin of the fire control lever, and its rear engages with the short bottom arm of the sear. When this bar is to the rear during normal fire, the secondary sear is held out of its bent and also out of its engagement with the barrel extension by this action.
The safety pivot pierces the side of the receiver. A recess in the side of the hammer which receives this pivot to serve as a safety bar is cut out so that when the “safe” position is reached, the hammer can still be released by trigger pressure but will be halted in forward motion before it can hit the head of the firing pin.
On this design of universal safety, the sear is carried further to the rear on the left into a recess in the safety lever. The lever is cut to permit movement of the sear only at the fire and at the safe positions. It cannot function at any intermediate point. Thus when the hammer is up and the safety is applied, pulling the trigger cannot accidentally fire a cartridge, for as the hammer falls its fall is positively halted before hitting the firing pin.
Like all earlier Mauser military pistols, this arm is designed to be used with a stock shoulder holster. However it should be noted that the grip is larger and thicker than that of the standard Military Model pistol and the two stocks will not interchange.
While in theory this is an efficient police pistol, in actual practice the cartridges are discharged so rapidly and the muzzle elevates so quickly that it is not an efficient full automatic design. The full automatic feature is of value only in very unusual cases of emergency.
Following are the characteristics of this Mauser M712:
The caliber is .30 (7.63mm Mauser). It uses the standard 7.63mm Mauser cartridge as already described.
The overall length of the pistol is 11.3 inches. The length of the barrel complete with its chamber is 5.2 inches. (It must be remembered in this design that the barrel extension which houses the breechblock is an integral part of the barrel forging, extending back from the chamber and being suitably cut away to permit recoil travel and also to house the breechblock assembly).
The weight of the arm is 2.79 pounds without the stock and with the 10-shot magazine inserted but empty. With the 20-shot magazine (empty) inserted it weighs 2.9 pounds.
The arm may be loaded from Mauser clips from above or by insertion of box magazine from below as already outlined.
While the rear sight is graduated to only 1000 meters, the cartridge in this pistol has an extreme range of about 2200 yards.
The muzzle velocity with standard barrel is about 1392 feet per second and the muzzle striking energy about 366 foot pounds.
At 50 meters the penetration is 8 to 9 inches in soft pine.
This weapon may be immediately identified by the Mauser trade mark on the left side of the receiver to the rear of the sliding fire control plate. It is manufactured of the finest materials to the finest standards of workmanship. It should not be confused with arms which look very much like it which were made in Spain; those are differently constructed mechanically and are neither as strong nor as reliable. The original Mauser M712 was first generally marketed in 1931.