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