Brazil’s Uru SMG: The Search for Extreme Simplicity
Text and Photos by Ronaldo Olive

Since the German Bergmann (Schmeisser, if you will) MP18,1 submachine gun made its early – though very limited – operational debut in the closing stages of World War One, this class of weapon has been the subject of countless design variations; probably one of the widest recorded in the history of firearms. This is certainly due to its inherent and comparatively simpler blowback method of operation, more often than not firing from an open bolt position, plus the fact that SMGs use pistol-type ammunition that are less structurally demanding on the weapons than more powerful rifle-caliber rounds. Sure, the 1920s and 1930s witnessed submachine guns embodying enormous amounts of strong, but expensive, machined components: the U.S. Thompson being a typical representative. World War Two, on the other hand, came up with a bunch low-cost, nonetheless effective, submachine guns as exemplified by Germany’s MP38/MP40, Britain’s Sten, Russia’s PPD, PPS, and PPSh, as well as the American M3 Grease Gun. All this considered, then, submachine guns have frequently emerged as the primary choice when a country decides to embark in a gun production program.

Brazil was no exception. In the early 1950s, Indústria Nacional de Armas S.A., a São Paulo-based private concern, produced substantial numbers of the INA M.B.50 and M.953, .45 ACP-caliber local versions of the 9x19mm Danish Madsen M1946 submachine gun. This was widely used by the Brazilian Armed Forces for over two decades, until replaced by the 9x19mm Mtr M9 M1972, a locally-made Beretta (later, Taurus) M12, the ubiquitous INA then being generally transferred to police forces use. Brazilian Army’s Fábrica de Itajubá (now IMBEL) played around with 9x19mm prototype submachine guns from 1970 to around 2000, but the various prototypes built and tested never made it to the production line. Some other designs from different local sources also materialized for testing and small pre-production batches, but the first indigenous submachine gun to reach actual series manufacture was an ugly duckling: the Uru (the name of a small Brazilian bird).

The mind behind this SMG was Olympio Vieira de Mello Filho, from Rio de Janeiro. During the 1950s, he and Nelmo Suzano, another Brazilian gun wizard, founded and operated a small firm called O.N. Gunmakers (the English language name after their initials appeared to give them more credibility) to make and sell high-quality hunting rifles for a selected clientele from Brazil and abroad. The custom guns were chambered to such calibers as basic 7x57mm Mauser and .30-06 to heavies such as .458 Winchester Magnum, .460 Weatherby Magnum, and .500 Nitro Express, and many remain on proud display at private collections worldwide. In the late 1960s, Olympio was working at the Brazilian Army’s renowned IME - Instituto Militar de Engenharia (Military Engineering Institute) in Rio de Janeiro and participated in the design of a 7.62x51mm general-purpose machine gun, the IME ARM-02 Maria Bonita and the subsequent Uirapuru, both never reaching the production stage. By 1972, he briefly took part in a Rio de Janeiro-based company, Bérgom S.A., again in partnership with Nelmo Suzano.

Around 1974, however, Olympio opted to go ahead and carry out individual gun projects of his own. While virtually secluded for a full month in a country house he owned well inside Rio de Janeiro State, he concentrated in elaborating a submachine gun project whose basic parameters were the use the smallest possible number of parts and being of easy, low-cost production. He usually said: “The fewer components you use, the lower malfunction potential you get.” In a three-month period, a hand-made prototype was completed by the end of the same year incorporating not only the original expected characteristics, but working flawlessly, as well. In 1975, Olympio managed to get himself a financing partner and established the Mekanika Indústria e Comércio Ltda. company with modest facilities in the Penha suburb of Rio de Janeiro. It was there that a small pre-production batch was completed, the guns being basically used for initial demonstrations and the official certification program carried out by the Brazilian Army at its Campo de Provas da Marambaia (Marambaia Proving Ground) in Rio de Janeiro, a pre-requisite for the series production and commercialization stages. This began in 1979 as the Uru Modelo 1, which differed from the prototype and pre-series examples by a number of details such as the redesigned tubular stock, longer magazine housing, adoption of an inertial bolt blocker in addition to the fire selector applied safety, and a slower (from about 990 to 750 rounds/min) cyclic rate of fire, which was achieved through the increase of bolt weight from 530 to 685 grams.

Technical Details and Specifications

Chambered to the 9x19mm cartridge and operating in the conventional blowback method from an open-bolt position, the Uru is largely built from tubular elements and stampings, the major components being assembled by welding and spot welding, with heat-treated alloy steels being used in parts subject to wear and shocks. Some investment casting parts (the combined trigger/sear, for example) are also used. The lower receiver is a box-like stamped rectangular structure totally open on the top from which protrudes the 105 mm long magazine housing, the plastic pistol grip and the large trigger guard. The stamped steel walls of this main body are 1.5 mm thick on the sides and bottom, being reinforced to 3 mm at the forward and rear ends. Attached to this by two pins in the lower receiver (a fixed one forward and a spring-loaded one at the rear) comes the 35 mm diameter, 2 mm walls, seamless tubular receiver. The two attaching blades double as bases for the fixed sights and the sling support points. The upper receiver houses the bolt (with a fixed, machined firing pin) and the small diameter recoil spring with its integral guide rod, both being inserted from the forward end. The 175 mm long barrel (six grooves, RH twist, muzzle velocity 390 m/s) has an integral mounting nut and is mostly contained within the forward end of the receiver, which acts as a shroud, ventilation being provided by thirty-six 8 mm diameter orifices in that area. A lightweight (430 grams) all-metal tubular shoulder stock attaches to the rear end, and this can be quickly removed from the gun by pressing a spring-loaded button on top, this reducing the overall length from 671 to 433 mm. What one was supposed to do with the stock after it had been detached from the gun was, often, the subject of (mostly, unprintable…) comments, so Olympio devised a right-folding stock wire variant that was offered as an option. Although slightly heavier (495 grams) and 30 mm longer than the original, it was much more practical and provided a better shooting position. However, virtually all guns came from the factory with the removable tubular stock. The weapon’s emphasis on ruggedness is also observed in its twin-row, single-position feed 30-round magazine, and Olympio clearly based it on the MP38/MP40 model. It was strongly built from a 1 mm thick stamped metal sheet, the 140 mm upper portion of its 240 mm overall length being double-walled to full 2 mm, this including the feed lips and assuring remarkable stiffness to that crucial (in any firearm) component. As single position feed magazines are inherently more difficult to load by hand, the gun came with a handy magazine filler. Basic weight specifications are: gun without stock and magazine: 2.6 kg; with stock, without magazine: 3 kg; complete weapon, loaded: 3.7 kg; empty magazine: 0.30 kg; loaded magazine: 0.65 kg.

At an early stage, Olympio made several sound suppressors for his gun. These, however, were not screw-on jobs, but were units with their own integral barrels: you just removed the original barrel, replaced it with the new unit, and you were ready to go. The built-in barrel was about 75 mm long, and was followed by a 32 mm long expansion chamber and 48 conical metal baffles along 300 mm of the suppressor’s 415 mm overall length. Weight was 910 grams. The suppressor employed the standard fixed sights of the gun, factory-set for 50 meters. A few cans made by Olympio featured sights (fixed “U” notch at the rear, fully-adjustable post front sight, both having huge protection ears) on them, and were intended to allow more precise shooting at 100 meters or so. The designer also experimented with at least two types of screw-on compensators/muzzle brakes between 1981 and 1983. Since the Uru was, on its own, very stable and controllable in full automatic fire, the addition of the devices was kind of a designer’s search for the ultimate SMG. Oh, yes, the gun became much noisier!

Manufacture Developments

About 3,000 examples of the basic Uru were manufactured by Mekanika in Rio de Janeiro between 1979 and 1983, when production was transferred to Vigorelli S.A., a traditional Brazilian sewing machine factory, in São Paulo, with a further 7,500 guns being completed by 1985. Early in 1986 while working for a Rio de Janeiro-based company, Brasarms Indústria e Comércio, and a few months before dying from a pulmonary disease caused by his heavy smoking habits, Olympio completed the prototype of what he called the Uru II. This featured the already-mentioned foldable wire stock and included the following modifications: no barrel ventilation holes in the receiver, a wooden handguard, new sling attachment points, protected iron sights with a longer radius, and a longer trigger. Internally, however, the only change was the replacement of the flat spring commonly used by the trigger and the magazine release lever by a coil type.

In 1988, the remaining stock of parts and the manufacturing rights were transferred from Vigorelli to Indústria e Comércio de Máquinas e Peças Bilbao, also in São Paulo. Through the company’s FAU Guns Division (initials of its owner, Spanish-born Francisco Alava Ugarte), marketing efforts were retaken on what the company also called the Uru II, in which the original inertial bolt-locking system was replaced by a locking safety lever located at the rear of the pistol grip. Apparently, 1,500 guns were manufactured in this configuration, in addition to having the barrel threaded to receive a screw-on sound suppressor made by FAU Guns, too. Curiously enough, the new company’s marketing wizards went on to even change the meaning of the name Uru, from that small Brazilian bird to “the metal from which an old Viking legend claims that the legendary Thor hammer was made…” The new company also tried to sell .380 ACP variants of the gun, both a semi-auto-only, long barrel carbine model with a fixed wooden stock and a selective-fire version, although the Brazilian very restrictive gun control laws (milder at that time than now) would never allow civilians to own such an “aggressive” weapon as an SMG-looking carbine. As for the selective-fire model, one wonders why, say, an LE agency would prefer the .380 ACP round (reportedly giving the subgun a cyclic rate of fire of only 350-400 rounds per minute) over the 9x19 mm.

Early in 1997 the Uru program went back to the hands of a re-born Mekanika Indústria e Comércio Ltda. In association with PLANEV – Planejamento e Execução de Vendas Ltda, also in Rio de Janeiro, and Amadeo Rossi S.A. – Metalúrgica e Munições, from São Leopoldo, Rio Grande do Sul State, some modifications were incorporated to the design, this leading to a new batch of Brazilian Army certification tests at the Marambaia Proving Grounds. The result was ReTEx (Relatório Técnico Experimental, Experimental Technical Report) Number 1629/98, issued on July 9, 1998. A version chambered to the .40 S&W cartridge was also tested and, apparently, certified, but no orders came by. The main distinguishing features of the “new” Uru were a side-folding tubular stock (reducing overall length from 671 to 433 mm) and a longer trigger.

Along its life, no matter its undisputed qualities of strength, simplicity, and low price, the Uru suffered from mismanagement problems created by people whom Olympio had associated with. Actual official sales appear to have been limited to a few State police forces (those of Bahia and Mato Grosso being often mentioned), plus a frequently-reported “unofficial” sale to Surinam, former Dutch Guiana, whose truck-shipped cargo was supposedly intercepted somewhere by Brazilian authorities and confiscated. Be as it may have been, a fact is that Urus have for a long time been seized from the hands of local criminals, besides serving as inspiration for a number of clandestine-made derivatives.

A curious fact in the history of the Brazilian submachine gun took place in the early 1980s, when some foreign companies (Belgian’s Fabrique Nationale Herstal and the U.S. Maremont Corporation, among others) demonstrated interest in possible joint programs to sell the Uru in the international market and asked for samples to be examined and tested. To everybody’s surprise, sometime later (1983), Maremont’s Saco Defense Systems Division announced and began promoting its Model 683 submachine gun which, at the earliest glance, showed that it had been strongly based on the Brazilian weapon. Here and there the American clone displayed cosmetic changes, such as a curious carrying handle incorporating a non-optical tubular sight, a telescopic tubular stock, a reshaped fire selector, a repositioned magazine release button, a muzzle brake, a slightly reshaped pistol grip, and longitudinal ventilation openings around the barrel. It seems that a legal dispute followed, and Saco subsequently was forced to give up its SMG program after having completed a bunch of prototypes. At least one is in C. Reed Knight, Jr.’s collection at the Institute for Military Technology in Florida.

Handling, Firing and Take Down

It was a general feeling that the Uru was a Jeep-type gun, not only from its Spartan looks but also from the impressions when you started handling and firing it. This author was lucky enough to have had close contacts with its designer and, thus, could follow its evolution during the first half of the 1980s or so. Here are my impressions dated about 30 years ago:

Typically, the 30-round magazine can be hand-loaded using the filling tool provided in just about one minute, no sweat. In Belgium, the guys at FN Herstal managed to squeeze in 34 rounds during their tests there. The magazine fit snugly into the slightly flared bottom mag well, whose hefty size generally prompted it to be used as a forward grip. The large release lever located at the rear was pulled backwards to allow the magazine to be removed, this requiring considerable pressure and not easily allowing a one-hand (remove-and-put away) action. Most shooters, the author included, used the firing hand to pull back the lever and the supporting hand to remove the empty magazine; an awkward procedure that worked fine, anyway. The cocking piece was a small button located about 45 degrees to the right and easily reachable by either hand. It was pulled back for about 60 mm and a “click” told you it had been caught by the sear, an integral part of the trigger itself. The size and shape of the cocking handle required an actual grasp with the fingers, as a possible attempt to use the base of the hand might result in the small button slipping past and eventually making the bolt run forward and chamber/fire a round. I saw that happen a couple of times...

The fire selector was a small half disc shaped affair on the left side, above the pistol grip, with the settings “A” (Automatic) to the rear, “SA” (Semi-Auto) top, and “S” (Safe) front. The safety position solidly blocked the trigger action and allowed the gun to be carried in the cocked (bolt to the rear) condition at to risk. In addition to that, the Uru incorporated a clever and sturdy inertial locking device that efficiently blocked the bolt travel after a 10 mm-only displacement in case of drops or blows on the back, thus avoiding accidental discharges. My various and frequent attempts at cheating the system into failing (no ammo loaded, of course) showed that it worked impeccably all the time, but Olympio frequently did the same (loaded gun) with a hand on the barrel muzzle! In spite of the fire selector’s position, it was not, in fact, within easy reach of the firing hand’s thumb, so the supporting hand could do the job at a blink of the eye.

The very simple fixed sights (peep 2 mm diameter rear sight, blade front sight, radius 230 mm) were built in the two transversal receiver mounting plates, together with sling attachment points. The factory-supplied tubular stock provided adequate support for shoulder firing and also for underarm tuck, but the subsequent folding wire stock, 30 mm longer and with a lower butt plate, was immensely better under the aspect of operational flexibility and for offering a better sight picture. Firing the Uru under all conditions was a good experience, even if done with the stock removed (or the later stock side-folded). Full-auto controllability was pretty good, thanks to the combination of the moderate (700-750 rounds/min) cyclic rate of fire and the gun’s weight (slightly over 3 kg). The supporting hand was equally comfortable holding the magazine well or the receiver. A minor design flaw showed itself to shooters with small, thin hands: the 13 mm gap that existed between the trigger and the lower part of the trigger guard would allow a skinnier index finger to slip past, a real hazard in an emergency situation. Sometime later, however, Olympio addressed the problem and came up with an adequate-sized trigger; but few guns were in fact so produced.

When you went ahead to field strip the Uru, you fully realized the design’s extreme simplicity. Using, say, a bullet tip to press the take down button at the rear of the lower receiver, the tubular receiver was swung open and removed from the main body. Looking inside the gun, you might think that parts were missing, since only nine components were to be found there. You shook it, and heard a few crackling, metallic sounds; an indication of wide tolerances. In demonstrations, it was often common to fill those innards with sand, earth or mud, give it a quick shake upside down, close the gun again and produce a long burst in full auto. In all, including magazine components and shoulder stock, the Uru had only 21 parts, and a full disassembly took no more than 40 or 50 seconds to complete.

This article first appeared in SmallArmsReview.com on August 9, 2013


Comments have not been generated for this article.