It looks like the whole thing started in late 1980 or so, when the U.S. Government, within its Joint Service Small Arms Program (JSSAP), issued an RFP (Request For Proposal) for the conceptual design and fabrication of a 9x19mm submachine gun. Historically, the U.S. Armed Forces, in contrast to most other countries, had not relied to a great extent on SMGs, the then-issued gun of this type being the .45 ACP M3A1 ‘Grease Gun’ of WWII vintage. What was expected was the acquisition of limited quantities of an intermediate weapon of advanced technology and usefulness to fill the gap between the .45 ACP M1911A1 pistol and the 5.56x45mm M16 rifle. In fact, a mixture of foreign and domestic submachine guns had been purchased for use by special operations forces of all the services, security forces, armed vehicle crew members, and for the enforcement of laws and treaties by the U.S. Coast Guard. It was generally wanted to develop a supportable, very reliable and effective weapon by advancing the appropriate technologies associated with submachine gun designs, the RFP describing desired characteristics that were not entirely satisfied by the designs then available. However, the Government’s specifications were somewhat self-contradictory in that they asked for reliability and maintainability on the one hand and, on the other hand, they were requiring features which would overly complicate the weapon’s design. Some of them:
The 9x19mm weapon might be easily converted to .45 ACP caliber, and also be capable of functioning in the full- and semi-auto modes from both the open- and closed-bolt firing configurations, with emphasis on the closed-bolt mode. Manual selection between the two modes could be either with a selector lever or by changing the assembly procedures of the trigger/sear mechanism. A 400-to-500 rounds per minute cyclic rate of fire was suggested, at the same time that some interest in a three-round burst selector at 1,200-1,400 or higher rpm was shown, this option being considered only if the weapon’s reliability and controllability were not compromised. Some physical characteristics included a barrel length in the 150 to 200 mm range and an empty (no ammo or sound suppressor) weight of not more than 3.2kg (1.8 to 2.7kg preferred). Other required features included a collapsible, folding or telescopic butt stock, minimum 30-round magazine capacity (if possible, with its long axis parallel to the bore!), an integral base for commercial collimated sights (e.g. at that time Quick Point, Single Point, Instasight, Tascrama, etc.). Many other detailed items followed, but will not be included here to keep my notes adequately sized.
At that time (late 1980-early 1981), Saco Defense Systems Division of Maremont Corporation contacted a U.S. company called Frentex Incorporated which acted as a liaison to Mekanika Indústria e Comércio Ltda., the Rio de Janeiro-based company that was beginning to series manufacture the Uru submachine gun (http://www.thefirearmblog.com/blog/2017/06/15/brazilian-9x19mm-uru-smg-reloaded/). The idea was to see whether Olympio Vieira de Mello Filho, the weapon’s designer, might come with suggestions capable of meeting the strict JSSAP requirements. It seems that some production examples reached the U.S. for a hands-on evaluation by Saco Defense, and at least two (a prototype and a production model) were submitted to highly-successful firing tests in Europe by Fabrique National Herstal in about 1981. It was no small coincidence that FN and Frentex were business associates, which somehow makes a Saco-FN connection apparent.
It just so happened that in 1983, Saco announced and started promoting its Model 683 submachine gun, which included the available granting of license production to other countries. Just a superficial look at it showed that it was, to all extents and purposes, an Uru clone, and I clearly remember Olympio’s WTF-type reaction when I showed him pictures of the weapon in the prominent “Jane’s Infantry Weapons” annual… I never knew if the promised legal sanctions were actually carried out by Mekanika at that time, and since no actual contracts materialized from the M683 affair, the whole thing fell into complete obscurity… until a spark of memory came to my mind when I saw that Corey R. Wardrop, Museum Curator of the Institute of Military Technology, in Titusville, Florida, was a colleague writer here at TFB. I vaguely remembered a 1980s article on the “six-eight-three” in a U.S. publication saying that the featured gun belonged to C. Reed Knight, Jr’s collection, and one thing led to another. Corey was kind enough to locate three of those Saco-made SMGs in the Museum’s inventory and was able to take the excellent pictures I’m sharing with you now. Thanks, Corey!
In a very concise analysis, the Saco Model 683 had the general Uru configuration to which some cosmetic changes were added. More evident were the retractable tubular stock, the slightly reshaped pistol grip, the longer trigger, the longitudinal ventilation openings (rather than orifices) around the barrel, the addition of a flash hider, and the light supporting structure for the plain optical (non-enlarging) sight. My surviving notes from that period show that both 25- and 32-round magazines were made, the gun’s loaded weight being in the 3.3-3.5kg range.