As already mentioned in an earlier TFB article, Brazilian police agencies were quick to follow a trend to adopt the .40 S&W round, introduced in the early 1990s as a wonder solution for most LE pistol and submachine gun needs. The local IMBEL – Indústria de Material Bélico do Brasil company soon came out with a somewhat crude SMG prototype (https://www.thefirearmblog.com/blog/2017/07/12/early-40-sw-subgun-prototype-brazil/) to initially explore the concept. The results were positive enough to justify the start of a brand-new design effort in 2000 or so, officially designated SMTR (Submetralhadora, Submachine gun) .40 IMBEL MD1. The brain behind the project was Army then-Captain Paulo Augusto Capetti Porto, the enthusiastic head of the Fábrica de Itajubá (Itajubá Factory) research department and who had had prominent participation in IMBEL’s work on a number of creative 5.56x45mm rifle developments (https://www.thefirearmblog.com/blog/2017/05/18/filfilc-97-family-forgotten-imbel-rifle-prototypes/).

Never seen before together in a photo: the concept-exploring prototype made by IMBEL’s designer Jair (“Jairzão”) Lins da Silva, on top, and that of Captain Capetti, which followed it. The earlier gun featured an M1911 short-recoil breech locking system, most unusual in SMGs.

The first prototype was a blowback-operated job firing from the closed-bolt position with a hammer/firing pin assembly based on the one used in the FAL rifle, a pretty much expected, time-saving solution from a long-time manufacturer of that 7.62x51mm rifle, from which the raked pistol grip and firing mechanism housing (i.e., lower receiver) were also hereditary. A three-round burst facility was added to the fire-selector, not exactly because it was needed, but rather because it was available at the research department shop (it had been developed and manufactured for a side-requirement involving  5.56x45mm rifles). The housing for the 30-round magazine, resized from a .45 ACP unit of a local INA M.B.50/M953 submachine gun, was somewhat ahead of the trigger guard, a small blade at the lower rear end being pressed inwards to actuate the release action.

Of all-steel construction, the “01” (author’s designation) prototype of SMTR .40 IMBEL MD1 shows the unmistaken FAL firing mechanism housing and pistol grip.

The retractable stock was a no-frills wire unit of the type somewhat immortalized by the U.S. M3/M3A1 “Grease Gun” of WWII fame and that has frequently appeared in SMGs everywhere when low-cost and simplicity are design parameters. Another cost-saving item was the cylindrical bolt, which was lathe-turned rather than squared up. The side-mounted charging handle could be optionally field-changed to either the right or left position.

The gun with the wire stock fully extended. The carry handle-type structure had top rails for accessories, while rear and front openings allowed the iron sights to be used all the time.

The flip-type rear sight, protected by side ears, came straight from a FAL, the same being the case of the hood-protected front sight post, this being mounted on a slightly-elevated base. Sight radius was 310mm. In addition to that, the subgun had a raised, carry handle-type structure with a railed top for add-on items. It is recorded that this gun worked flawlessly during the in-house test program, including having been feed with large amounts of +P rounds.

The cocking handle (missing, in the old, not-too-sharp photos used here) was designed so as to be field-changed for right- or left-side manipulation.

Basic specifications of this “01” (my designation) prototype included a 135mm suppressor-ready  (threaded) barrel, an empty weight of 3.2kg, and an overall length of 655mm (450mm, stock retracted).

One more view of the very first SMTR .40 IMBEL MD1 prototype. It may be noticed that the side walls of the original INA M.B.50/M953 .45 ACP magazine were pressed inwards to size it to the .40 S&W rounds.

Yep, higher-resolution (though not necessarily sharper) photos are available here: https://imgur.com/a/8ka9Q