Poland's steel crayfish: the PM-63 Rak machine pistol

A submachine gun or a fully automatic self-loading pistol with shoulder stock? This is the question that arises when you look at the 55-year old Polish PM-63 Rak. It doesn't fit into either categories, but it does fit easily into a hip holster – thanks to its length of only 13”/33 cm and a weight of 3.9 lb/1.8 kilograms. Even the model name does not answer the question. Although the abbreviation "PM" stands for "Pistolet maszynowy", "machine pistol"  in English, "Rak" stands for "Ręczny Automat Komandosów" ("commandos' hand-held automatic" ) in official usage. Furthermore, designer Piotr Wilniewczyc (1887-1960) might have had his own intuition. 

Some claim that the Pole designer named the gun this way after its unusual appearance. Because when cocked, it looks as if it is being held backwards. This is why he jokingly called it "Rak" (in English: "crayfish"), in reference to the characteristic of crayfish to "move backwards" and "forwards". Other weapon historians claim that Wilniewczyc named it "Rak" – that in Polish also means “cancer” – because he was seriously ill with cancer and suspected that he would hardly live to see the weapon completed. Be that as it may, Wilniewczyc's "steel crayfish/cancer" is worthy of close examination.

Poland's steel crayfish: the PM-63 Rak machine pistol
The PM-63 Rak measures 23”/583 mm with the stock extended, but the small butt-plate flap at the stock end is almost useless.

PM-63 Rak: a product of the Polish 1950s

From the mid-1950s onwards, Poland's army was looking for a handy machine pistol. It was to be used as a sidearm by vehicle and aircraft crews, paratroopers, gunners and military policemen, it was to fit into a hip holster and be the weapon of choice for Boris V. Svemin's new standard cartridge of the Warsaw Pact, the 9x18 mm Makarov. The design was entrusted to Wilniewczyc, the father of the Vis wz.35 Radom pistol

He had already been involved in the development of the Mors wz.39 submachine gun and in 1957 he presented the WiR wz.57, a semi-automatic pistol in 9 mm Makarow at an advanced prototype stage. Despite his illness, Wilniewczyc set to work with zeal. Knowing that he would have little time left, he first looked at what other designers had come up with. 

Poland's steel crayfish: the PM-63 Rak machine pistol
The barrel of the PM-63 Rak is fixed in the frame and locked in place with 5 sturdy ribs in corresponding grooves in the frame.

He found what he was looking for at the Czech Samopal vzor 23/25 of the brothers Frantisek and Josef Koucky. This was the first machine pistol with a telescoping bolt, so it was extremely short and had a magazine well into the pistol grip. Wilniewczyc also liked the folding stock, whose butt plate served as the front grip when folded, and the two-stage progressive trigger. With this, the technician saved the time needed to create a real fire selector lever. 

Furthermore, it can be considered certain – without any evidence – that Piotr Wilniewczyc also inspected the Uzi designed by Uziel Gal (born Gotthard Glas). After all, it was considered to be groundbreaking: it also had a magazine well in the pistol grip and a bolt that partly wrapped around the barrel.

For the PM-63 Rak, the Kouckys with a hint of Gal

A view from above of the the frame barrel grooves of the PM-63 Rak.

Wilniewczyc merged the essence of Gal's research with his own ideas and presented a first working study of the PM Rak at the end of the 1950s. This caused people to sit up and take notice. Instead of the usual submachine pistol-style receiver in which the bolt moves back and forth, the PM-63 Rak external bolt slides in guide rails on the grip – just like a conventional semi-automatic pistol. However, Wilniewczyc's gun fires from an open bolt and the barrel, is rigidly connected to the frame by five ribs. 

Wilniewczyc tinkered with his last gun until 23 December 1960, when the cancer took him away. The rest of his team, Marian Wakalski, Grzegorz Czubak and Tadeusz Bednarski, completed his work and presented a near-series version of the Rak in 1962. It was very compact, with an unconventional but sturdy technology, an unmistakable appearance and six astonishing detail solutions:

PM-63 Rak – Detail 1: a matter of tact

Like the Czech Samopal vzor 23/25, the PM-63 features a two-stage progressive trigger. If this is only pulled halfway, it fires single shots. If it is pulled all the way back, it fires full auto. Interestingly, the Polish copy of the Czech idea is technically different – and it works perfectly, even with gloves on.

PM-63 Rak – Detail 2: the right rate

Poland's steel crayfish: the PM-63 Rak machine pistol
The two-part weight of the rate reducer is hidden in the back of the PM-63 Rak's slide.

The fire rate reducer is as simple as it is effective, consisting of a spring-loaded weight in the rear part of the slide, and a spring-loaded lever raising from the rear part of the frame. How it works: when the slide moves backwards after a cartridge has been fired, the weight travels back with it. While the slide is in its rearmost position, the weight moves rearward even further against the pressure of its spring. 

This reveals a slot in the underside of the slide, allowing the spring-loaded retarder lever to engage the slide and keep it open until the weight – accelerated forwards by its spring – pushes the retarder lever down again with its conical head. 

Poland's steel crayfish: the PM-63 Rak machine pistol
In the grip of the PM-63 Rak is the spring-loaded lever.

Only now the slide can move forwards again and the next cartridge is fired. This simple mechanism reduces the rate of fire from theoretical 900-1000 rounds per minute to 600-650. When the trigger is fully pulled, i.e. in full-auto, the disconnector remains inactive. However, if the firing finger pulls the trigger only halfway through (single fire), the disconnector keeps the slide open until the trigger is released again (trigger reset). 

In the beginning the rate reducer weight consisted of a piece of tungsten. At the back of the rate reducer the weight changed into a rod, which guided the spring. Because of the high costs the military demanded cheaper steel weights. But because steel is lighter than tungsten, they had to be longer. As a result, the steel weights increased the wear – and broke. Only two-piece steel weights solved the problem.

PM-63 Rak – Detail 3: the spoon

The slide front is striking, as it is shaped like a spoon. The trough-shaped slide projection acts like a compensator, pushing the muzzle downwards under the effect of the gases escaping from the barrel in full auto. On the other hand, the spoon serves as a cocking aid: if the front of the PM-63 is pressed against a hard surface (a floor, a wall, a vehicle), the weapon can be cocked easily, positively and above all with just one hand (!).

PM-63 Rak – Detail 4: more than just a magazine

Poland's steel crayfish: the PM-63 Rak machine pistol
The lever in the frame of the PM-63 Rak engages from below through a slot in the slide and keeps it open until the weight slides forward again and pushes the lever down.

While the extractor is conventionally located on the right, in the bolt face of the slide, you will look in vain for the ejector at first. No wonder, since only a small projection at the rear end of the left magazine lip serves as an ejector. This works perfectly – as long as the magazines are handled carefully.

PM-63 Rak – Detail 5: fold, extend, rattle

The folding foregrip looks very modern for a design that is around 55 years old. Like the spoon, it was born out of necessity: the Radom engineers considered the original version of the PM-63 to be too dangerous. The reason: similarly to the AKS, it had a metal stock that could be folded under the weapon, with a rotating U-shaped butt plate. This allowed the weapon to be fired from the shoulder like a sub-machine gun, one-handed like a pistol with the stock folded under the fore end, but also two-handed with the stock folded and the butt-plate used as a forward grip. 

Poland's steel crayfish: the PM-63 Rak machine pistol
View of the lever mechanism in the frame and slide of the PM-63 Rak.

But with the PM-63 the shooter's hand would have been under and even slightly IN FRONT of the muzzle! The Radom engineers therefore came up with the spoon-shaped slide projection, which solved two problems at once: it protected the hand and reduced muzzle climb. Of course, this forced the shooter to cock the gun before the folding stock could be swung open. His hand would have had to be swept again in front of the muzzle. The Radom engineers therefore conceived a double-sided extendable stock with a (largely useless) butt plate and replaced the initially wooden fore-end with a plastic version featuring a folding foregrip

Both improvements made sense – and today their basic idea, although more durable and stable, can be found on the HK MP7. On the PM-63 Rak, the stock and foregrip are of limited use: too delicate, too rickety and with too much play.

PM-63 Rak – Detail 6: a machine pistol for a hip holster

In terms of dimensions and weight, the PM-63 Rak does not have to shy away from comparison with the MP7. At 13”/33 cm in length and weighing 3.5 lb/1.6 kg (without magazine), it is hardly longer and heavier than a classic full-steel gun and fits into a thigh holster. But only with a 15-round magazine instead of a 25-round magazine.

Poland's steel crayfish: the PM-63 Rak machine pistol
The spoon-shaped slide projection serves as compensator, hand protection and cocking aid at the same time.

The PM-63 Rak machine pistol is put into service

After extensive testing, the Polish Army accepted the gun in 1963 as the "9 mm pistolet maszynowy wzór 1963 (PM-63)". In 1964 the production facilities were established in Radom, but it was not until 1967 that production really started. The soldiers critically examined the gun – and revealed weak points. For example, the slide slamming to the rear destroyed many a gas mask glass and demolished the teeth of quite a few shooters inexperienced in handling the weapon – hence the nickname "the Polish Dentist".

Poland's steel crayfish: the PM-63 Rak machine pistol
The extendable stock of the PM-63 Rak is frail, but easy to operate: to extend, press the side rocker lever...

Also the large magazine release catch at the back of the magazine well was often unintentionally operated, causing the magazine to drop out of the gun. From 1969 on there was therefore a smaller magazine catch, a little later even only a small sheet metal lever, which is de facto no longer operable with gloves. 

Also the often jammed locking mechanism for the stock had to be optimized and a bracket for the rate reducer lever had to be installed to eliminate lever over-travel. This is because if soldiers inserted the slide on the grip when re-assembling the stripped weapon without first positioning the lever properly, the latter would be damaged. 

Poland's steel crayfish: the PM-63 Rak machine pistol
...then turn the butt plate upwards and through 270 degrees with the stock extended.

Furthermore, changes were made to the recoil spring. Initially, it ran on a two-piece telescoping spring rod in a deeply drilled channel. As a replacement, a simpler spring was available, guided only by one rod placed in a milled groove. This saved money in production, but made disassembly and re-assembly more complex and lengthy. The replacement of the barrel, which was hard chrome-plated inside and out on the first models, with a blued steel one was also only a matter of cost. Only the feed ramp, the chamber and the bore were now chrome-plated.

Poland's steel crayfish: the PM-63 Rak machine pistol
Finally, to lock the stock, press in the small lever at the rear bottom of the frame.

Between 1967 and 1977, around 70,000 PM-63 Rak were produced in the Radom gun factories. In addition, a 9 Para version was designed at the request of the Cenzin Foreign Trade Office, which exported the PM-63 from the early 1970s. In this version, the 1.2 lb/550 g slide was considerably heavier and the grip design differed from the PM-63. However, only about 20 were made

Special barrels provided further variations. One of them allowed to fire full-auto with blanks. The other – for special units – was longer and threaded for the mounting of a suppressor. The suppressor was fitted with front and rear sights, since it obscured the standard sights.

PM-63 Rak: popular with "the good and the bad”

Apart from the Polish military no other army used the PM-63 Rak. However, the SWAT teams of the Polish police, the Polish Railway Police and private security services did. The "small PM-63 machine pistol" also enjoyed great popularity with the Volkspolizei of the GDR (VoPo). After the fall of the Berlin Wall, the police of the Free State of Saxony continued to rely on such PM-63s from old VoPo stocks for some time. 

The PM-63 Rak was also popular with outlaws and terrorists. Members of the RAF presumably used illegally procured PM-63 via channels from the GDR/Palestine. 1977 demonstrable users were the hijackers of Hanns Martin Schleyer, the Palestinians in the fight for Beirut, Iranian anti-Khomeini dissidents in the attack on the Iranian embassy at Princess Gate (London, 1980), General Noriega's irregular troops in Panama and one of the terrorists who hijacked Flight 139 in Entebbe on 4 July 1976. PLO leader Yasser Arafat was also photographed in the 1990s with a suppressed PM-63. Unfortunately, there is no documentation anywhere on record of whether the Polish Dentist gave at least the one or other bad guy a toothless smile...

Poland's steel crayfish: the PM-63 Rak machine pistol
 Truly an "eventful history" behind it: Poland's unusual PM-63 Rak machine pistol.
This article is also available in this language: