At the end of the 1950s the Italian economy was booming, thanks to both the creativity of manufacturers and the enormous boost provided by the Marshall Plan. It is not a coincidence that in this climate of general improvement in prosperity, specifically in 1959, Beretta presented the PM12 submachine gun. In Gardone Val Trompia, in the heart of the Italian arms producing region of Italy, the “Fabbrica d’Armi Pietro Beretta” (Italian Arms Factory Pietro Beretta) was prepared for modernized production.
The design and creation of the PM12 reflects the general abundance of a “can do attitude;” material, creativity and the economic resources of the time.
The PM12 looks like a very simple product to manufacture, however, its ingenious design was not cheap, let alone simple to produce. The simplicity element refers to its ease of use and not design and manufacture which combined resulted in a highly accurate firearm.
In order to better understand how the PM12 came to be one should take a brief look at a couple of the PM12’s predecessors.
The Beretta SMG (Sub Machine Gun) project took their cue from the “O.V.P.” (Revelli patented LMGs – Officine Villar Perosa) starting with the “18” and “18/30” models. The Gardone factory produced one of the best firearms of its day in 1938, the model 38A M.A.B. (Moschetto Automatico Beretta – Beretta Automatic Carbine).
It differed very little from the then current operating principles of SMGs using a blow back operating system with a fixed firing pin on the bolt face, however, the combination of its design, manufacturing quality and ammunition (its 9M38 is a lot more powerful than the standard NATO 9mm cartridge) made it a formidable firearm.
It shared the same shortcomings of its predecessors in that it was slightly cumbersome when used by mechanized troops.
At the beginning of the 1950s it was decided that the SMG of the future needed to be as functional as the M.A.B. as well as being far more compact and safer to transport both on troop transport as well as on foot patrol. It had to be as the User Manual stated; “simple in both design and use,” possess “very good safety features” and be of “reduced size and weight.”
Furthermore, it had to respect a few more considerations such as being exceptionally suited to “urban warfare (QCB) and dense vegetation environments,” “operational use by mechanized forces,” “special forces as well as police patrols” and “general use for enforcing public order,” all of which meant that its pistol caliber ammunition had to be accurate and effective out to at least 200m (218 yards).
In 1951 the Beretta engineer Mr. Salza was placed in charge of the PM12 project.
The “Pistola Mitragliatrice” (Machine Pistol) PM12 is a 9mm Parabellum with blowback operated system which can be fired both in semi and fully automatic modes. The firing process is initiated by pulling the trigger with the bolt firmly in the fully pulled back position (i.e. fully open).
The trigger does not directly activate a hammer, it engages a bolt holding notch via a sear, which releases the bolt, which then races forward picking up a bullet from the magazine and when chambered, this is fired by the fixed firing pin. The bolt is thrown back directly by the expanding gases pressing on the case as the round travels down the barrel. As the bolt reverses, the extractor pulls the empty case back, which is then ejected via the ejection port positioned on the right of the frame, before the bolt reaches the end and the whole process is renewed.
A brief description of the blowback system might be useful for some readers. This operating system is different to that of most gas operated weapons in that they rely on gases (sometime regulated) entering the gas port and forcing a piston back which then pushes the bolt back; or in direct gas the gas enters a tube and exerts the pressure on the bolt carrier- generally these systems do not use a fixed firing pin.
A great advantage of having the barrel enclosed in the bolt, generally called a “telescopic system” is that it allows for more controlled shooting in full automatic mode as this design dampens the natural upward motion of the barrel. Another advantage of this system is its compactness as it measures a mere 16.5 inches (418mm) in length.
The compact nature of this design could well be the reason why the manufacturer decided to change the denomination of its SMG from “automatic carbine” to “automatic pistol” and to further emphasis its qualities as a weapon for use at very close range such as in buildings.
The Italian forces (military and police) stated that they would like to have a space beneath their seats (both driver and passenger seats) when recently asked what improvements could be made to their vehicles to further improve the ease of transporting the PM12S and S2s.
THE BARREL BOLT ASSEMBLY
The design of the bolt and barrel system is essentially a single functioning unit which was and still is a radical design and still represents a reference point for designers. The PM12s’s successor, the Beretta MX4, is based on the same bolt-barrel assembly principle.
Beretta’s new SMG, the MX4 has been a commercial success with minor adjustments made for certain large volume buyers and as mentioned its barrel-bolt combination is based on that of the PM12.
The PM12’s cylindrical bolt has been extracted from a solid rod of steel and is about 7.9 inches (200mm) long to which the cocking lever is firmly fixed.
The bolt has been drilled longitudinally to house the barrel and chamber section (one single mechanical piece). There is no closing breech as the end of the firing chamber simply makes contact with the bolt head with its fixed firing pin. The screw on rear cap retains the rear of the recoil spring.
The rear of the bolt is of a slightly smaller diameter than the rest so as to fit into the recoil spring. Moving forward along the bolt one finds the impressively large and powerful extractor. Thereafter, the cylinder retains the same external dimensions, however, it has been hollowed out in order to insert and extract the barrel which protrudes from a drilled hole at the front extremity of the bolt. Approximately 2/3 of the barrel’s length is housed within the bolt central cavity.
This design, combined with its notable mass and minimal moving parts shifts the center of mass far forward making it very stable when firing even with the lever on fully-automatic. Unlike the M.A.B. this design meant that there is no need for a muzzle brake.
The receiver has been moulded from sheet metal into a cylindrical shape with both ends blocked by screw-on caps, the forward one is to keep the bolt in and the other to retain the recoil spring.
The lower side of the receiver is the most complex part of the body as it houses the pistol grip, trigger assembly, magazine hold and the forgrip in an elegant but functional array.
The left side of the cylindrical receiver has a long narrow window for the cocking handle. The ejector port is housed midway along the right side of the frame.
The bases of both the fore and rear sights have been welded to the upper part of the receiver and both have large solid side walls to better resist knocks/impacts as well as doing their duty in helping to aim.
TRIGGER AND SAFETY SYSTEM
The selector lever is very functionally positioned between the top of the pistol grip and above to the back of the trigger so that it can easily be activated by the shooter’s thumb whilst gripping the weapon. There are three positions, moving anticlockwise: the “S” denotes the safety position, the “1” denotes semi-automatic mode and finally the “R” (raffica) denotes fully-automatic mode.
Unlike its predecessor the M.A.B. which has two triggers which functioned as a selector lever the PM12s has a more a classical single trigger which is housed in a large trigger guard allowing the user to shoot whilst wearing gloves. The trigger, by ways of internal levels, lowers the bolt retaining notch to commence firing.
The PM12 has two safety features, one automatic and the other manual. The early versions had a knob which had to be depressed. The safety activated by the selector lever was introduced on the PM12 S models. This change led to the commercial denomination of PM12 S.
The automatic safety is activated by the middle finger when gripping the pistol grip and the lever is positioned between the trigger guard and the pistol grip. As with similar systems, once the lever is depressed it frees the trigger mechanism and with the manual safety off the weapon is live.
When the PM12 is ready to fire the bolt is pulled back into the open position where it is blocked by the safety mechanism as it prevents the trigger from lowering the bolt catch;
With the bolt fully forward in the closed position and an empty firing chamber the bolt cannot be cocked because of a small notch activated by the safety lever.
This device makes the PM12 a very safe weapon to carry and transport as accidental discharges are not uncommon in weapons with just a safety lever but where the bolt can be unintentionally cocked.
This potential problem had been partially rectified on the later models of the M.A.B. such as the model 38/49 type 5 which had an automatic safety which was deactivated when gripping the stock of the carbine.
The manual safety overrides the automatic safety further reducing the problem of accidental loading and discharges.
The latest version of the PM12; the PM12S2 even has a third safety feature which is has been built into the cocking handle and is connected to the frame by levers and springs. This device has provided a fertile ground of heated debate between those for and against it.
THE STOCK AND GRIPS
The simple ergonomic design of the weapon including the pistol grips and stock have over time also proven to be very functional for both carrying and shooting.
The weapon has two pistol grips, the rear one which is a part of the trigger assembly and trigger guard with two polymer grip covers. The front one which is positioned close to the muzzle is a simple classic pistol grip made from steel and polymer.
The standard stock is made entirely from steel and for ease of transport which can be folded a full 180 degrees with a collapsible butt stock which extends to fore pistol grip on the right side of the frame.
The stock is folded by depressing a lever positioned just beyond the actual folding point. The folded stock almost becomes flat with the right side of the frame and only protrudes by the diameter of the rod of the stock.
Beretta has produced a number of special components such as wooden stocks and high power flashlights encased in the fore pistol grip for special operations.
The PM12S uses traditional sights. The foresights can be adjusted using a special implement for both elevation and windage. The rear sights are flip aperture sights, similar to those of the M1 carbine, with holes set at different heights so that targets can be quickly engaged at a range of 100m or 200m.
Both sights have robust protective side walls to better withstand physical abuse.
The manufacturer has also made a range of accessories to personalize the weapon as well as supports to attach variety of sights such as red dot and holographic sights.
Four different types of finishing are used for Beretta’s PM12S. The surface of the steel bolt is treated with chromium with the small internal components are either blued or subjected to phosphate treatment. Parts that are exposed to the elements are phosphate treated and then covered in a film of epoxy resin which is essentially polymer.
The choice of the finish is dictated by the actual function of the component as well as the practicality of applying a particular finish. Ideally, all the metal components should be treated with an isolating film, however, even the small thickness of the film could hamper the movement of certain moving parts.
Generally, the phosphate treatment and films applied to the PM12 are only a few microns thick and applied to parts mainly exposed to the elements. The inside of the barrel has been treated with chromium and the external part with magnesium phosphate. The rest of the weapon is blued and all parts are routinely lubricated to improve isolation.
The only part of the weapon that is partially shiny is the bolt which has had chromium added to it via electrolysis to stiffen and make it more resistant to corrosion. This procedure is necessary as the bolt head and part of the bolt are subjected to the corrosive gases resulting from the firing of the weapon as well as the need to keep the bolt’s surface smooth to reduce the effect of friction and lower the chance of stoppages and or reduced rate of fire.
We asked four very experienced law enforcement officers who have extensive experience with the PM12 both as instructors but also during firefights to give a more authoritative view of the pros and cons of the PM12. The officers involved come from the Italian State Police and the Corpo dei Carabinieri. We asked each of them to briefly give their view of the weapon and have maintained their anonymity by replacing their names with letters.
A) “When I joined the Carabinieri the M.A.B. was still in use. Although it was an excellent weapon the arrival of the PM12S represented a notable improvement, especially regarding safety when on the move. The main failing of our M.A.B. was that it had no automatic safety and accidents did occur. The PM12 solved that particular problem.”
B) “The telescopic system was excellent when we needed to fire on fully automatic as it was easy to prevent the barrel from rising too much. We showed recruits just how stable and effective the PM12S was even when fired in fully automatic mode by emptying two whole 32 round magazines at targets placed 20m (65 feet) away and keeping a very tight grouping. We would teach them how to place well aimed shots at ranges beyond 100m (328 feet) in semi-automatic mode when on operations. However, it is fundamental that all recruits are given very adequate instruction in its use and fire arm safety to be able to serve the public well”
C) “It is an excellent weapon and I prefer it to a number of other weapons in our arsenal. It is an old style arm, but many special components have been made including MILSTD1913 rails to attach different devices we might need, however, it is very easy to fire instinctively and accurately with its iron sights. I do not like the third safety feature that was added to the PM12S2 as I don’t believe it is of any real use”
D) “Most of the PM12S’s critics have either had very little or no experience/training with this weapon. It really is an incredible weapon, but it requires a lot of training to be able to take full advantage of it. Having said that, it is certainly a very easy weapon to use and maintain in good working order as the design is simple and the PM12 is very robust. Our special forces within law enforcement use more modern and more sophisticated weapons. However, the PM12 is a very versatile weapon and will be in service with us for many years to come. New weapons do not improve our performance, only proper training can do that, well executed training makes the difference between a job well done and a potential disaster.”
A LOOK TO THE FUTURE
Beretta has come a long way since the original PM12 project. It is far more international, it is able to design and manufacture weapons to face the multitude of challenges we face today. Beretta has a specialist division called “Beretta Defence Technologies” which encompasses some of the best known brands forming part of the Beretta Group and collaborates globally with the military and law enforcement agencies to provide requested solutions.
A relatively new product which is a direct descendent of the PM12 is the MX4 which we will be testing shortly to closely examine the evolutionary process of this fantastic SMG.
Until there is a revolution in the arms industry where the current weapons and ammunition combination are superseded there will be a place for the venerable PM12 and its 9mm Parabellum caliber SMG ammunition.
Firing modes: semi and fully automatic. The firing cycle is initiated from an open bolt position.
Operation system: Blowback
Caliber: 9mm x 19 Parabellum
Ammunition: 9mm Parabellum (NATO Standard)
Muzzle velocity at V 0.5m: 430 m/s (1,411 f/s)
Kinetic Energy E at 0.5m: 77 kg/m (557 lb/ft)
Rate of fire: 550/650 rounds per minute
Length with folded stock: 418mm (16.5inches)
Length with extended stock: 660mm (26inches)
Barrel length: 200mm (7.9inches)
Rifling: 6 right turning grooves with a 1 in 9.8 inch rate of twist (1 in 250mm)
Height with a 32 round magazine: 244mm (9.6inches)
Weight without magazine: 3.200 kg (7lbs)
Weight of fully loaded magazine 0.570 kg (1.3lbs)
Rear flip aperture sights: 100m and 200m (328ft and 656ft)
Foresight: adjustable for both elevation and windage.
Distance between the two sights: 285mm (11.2 inches)
Safety features: manual via selector lever and an automatic safety lever deactivated (middle finger) by gripping the PM12 in a readiness to shoot.
External finishing: treated with magnesium phosphate followed by a film of epoxy resin to improve the weapon’s resistance to corrosion and general wear and tear. The plastic parts of the pistols grips have been given a glossy black finish.