The following information on the Mauser WTP-1 vest pocket pistol comes from Chapter 33 of Mauser Rifles and Pistols by W. H. B. Smith. Mauser Rifles and Pistols is also available to purchase in print.
In the course of its manufacturing history, Mauser produced two types of vest pocket-pistols.
The first of these arms, known as the WTP-1 (Westentaschen Model 1), was introduced to meet the demand in Germany for a native vest pocket pistol to fire the 6.35mm (.25 Automatic Colt Pistol) cartridge. It was designed to compare in size with the Colt Vest Pocket Automatic introduced in 1908 and its Belgian counterpart, the Baby Browning.
This WTP-1 Model was continued in manufacture until 1939. It is a standard blowback type of weapon, the low powered cartridge employed not requiring the use of a locking system other than that provided by the weight of the moving parts and the spring to be compressed. (In Germany this type is called “Federverschluss”—literally “spring locked”).
This pistol will use the standard United States caliber .25 Automatic Colt Pistol cartridge. It weighs only 11-ounces, is 4.5 inches overall in length, has a barrel 2.4 inches long, a maximum height of 3 inches, and is .75 inch thick at its widest point. The magazine holds 6 cartridges. By loading another cartridge in the firing chamber directly, the capacity is raised to 7 cartridges.
In general exterior appearance, it somewhat resembles the Colt design. However, it is not equipped with a grip safety as is the Colt.
Mauser WTP-1 Loading
The arm is loaded by pushing back the magazine catch in the bottom of the butt at the rear, which releases the standard steel box magazine to be withdrawn through the bottom of the grip section of the receiver. The magazine is loaded by pressing the first cartridge down on the front end of the magazine platform (or follower) and pushing it back under the overhanging lips of the magazine. Succeeding cartridges are started by forcing each one down on top of the one below it until the cartridge column is depressed enough that the cartridge may be slid back under the lips which overhang part of the top of the magazine to retain it. The loaded magazine is then inserted in the butt and pushed until it locks.
The serrated sections at the rear of the slide are then gripped by the thumb and fingers of the left hand while the pistol is held in the right hand, care being taken to see that the firing finger is not inside the triggerguard. Drawing the slide back to its fullest extent compresses the recoil spring mounted about its guide in the receiver channel below the barrel, to provide energy for the return movement of the slide.
As the slide is drawn back, it pulls with it the striker which is mounted in the rear breechblock section of the slide in line with the chamber. The spiral spring around the striker is compressed as the striker is withdrawn. The sear catches in the striker bent and holds the cocked striker in rear position. The spring in the magazine thrusting up against the magazine follower pushes the cartridges up, and as the solid breechblock section of the slide passes over the top of the magazine, the top cartridge can rise far enough to be in line with the breechblock when that unit goes forward.
Releasing the grip on the slide permits the recoil spring to pull the slide forward, and the feeding face on the breechblock, striking the top of the cartridge case in line, thrusts it forward out of the retaining lips of the magazine, and into the firing chamber. The extractor in the breechblock snaps over the cartridge case and engages in its extracting groove. The pistol is now ready to fire. There is a thumb-piece on the side of the receiver on the left which may be pushed up to lock the action so that the trigger cannot release the striker. Unless this thumb safety is applied, the pistol is now dangerous. When the striker is cocked, its head protrudes through the rear of the slide. Thus, if a protrusion can be felt or seen, one is warned that the arm is cocked, though the chamber is not necessarily loaded.
With the safety off (in the “down” position) pressing the trigger will force back the trigger mechanism to free the striker pin and let its spring drive it forward to fire the cartridge in the chamber.
Mauser WTP-1 Operation
As the cartridge is fired, the bullet travels down the barrel and the side pressure within the cartridge case forces the elastic brass case tightly against the walls of the firing chamber to act as a gas seal, while the rearward thrust of the gas within the cartridge case is transmitted to the face of the breechblock. Since the bullet is very much lighter than the breech assembly, it is out of the barrel before the rearward action has opened the breech appreciably. As the breechblock is blown back, the pressure within the cartridge case drops rapidly, and the cartridge case contracts. Thus the extractor in the face of the breechblock draws the empty cartridge case back with it until it is ejected through a port in the slide. As the slide goes back, it operates an interrupter mechanism which prevents the trigger from functioning until ready for the next shot. The breechblock during its rearward stroke, compresses the recoil spring below the barrel and also the spring around the striker. The sear catches the striker and holds it back as the recoil spring pulls the slide assembly forward to chamber the next cartridge rising from the magazine.
Before another shot can be fired, pressure on the trigger must be released to enable the trigger spring to push the trigger forward far enough to operate the interrupter so that contact can be made for the next pressure on the trigger.
A pocket pistol which would fire automatically as long as the trigger was held back would be an extremely dangerous instrument, as the pistol would rise rapidly after each successive recoil. This interrupter mechanism assures that only one shot will be fired with each pull of the trigger. It is possible for a pistol expert to fire about 6 shots in one second, however, with this arm. When the last shot has been fired, the magazine follower rises to interfere with the forward movement of the breechblock, thereby holding the breech open to inform the shooter that his pistol is empty. When the magazine is withdrawn, the slide runs forward. When a loaded magazine is inserted in the handle from below, the slide must again be drawn back, and released in order to chamber the first cartridge to start firing again.
Mauser WTP-1 Cartridge Specifications
The cartridge used in this weapon is the standard United States .25 Automatic Colt Pistol cartridge. This cartridge is known in Europe and South America as the 6.35mm Browning cartridge. It uses a powder charge of about 1.5 grains of smokeless and fires a 50-grain metal jacketed lead bullet. It develops a muzzle velocity of about 755 feet per second, has a striking energy at the muzzle of about 71 foot pounds and at 15 feet will penetrate 3 pine boards, 7/8-inch thick.
While this pistol is not considered an effective side arm in the United States, it has tremendous vogue throughout the rest of the world as a personal protection arm. It is the second most popular pistol caliber in the world, the first being the .32 Automatic Colt Pistol cartridge, known in Europe as the 7.65mm Browning cartridge.