The Tromboncino Modello 28 (lit. "grenade launcher model 28") was an Italian grenade launching attachment designed in 1928 produced by a number of Italian state arsenals in Brescia and Terni from 1928 to 1934. Seeing brief usage with the Italian Army before it was retracted from service, the Tromboncino serves as a precursor of sorts to the modern underbarrel grenade launcher.
History[]
In the 1920s, the Italian Army wanted a close-assault device for use in infantry platoons, and wanted it to be readily available (i.e. setting up not required) and could be used while its user was on the move. To do this, they mounted a grenade launching device on the side of a Carcano M91TS (Truppe Speciali, lit. "special troops") carbine; this was noted as being a rather ingenious solution.[1]
Production of the Tromboncino was outsourced to three arsenals in Brescia and Terni: Fabbrica Armi Esercito di Terni (Terni) based in Terni, Metallurgica Brescia gia Tempini (MBT) and Fabbrica d'Armi Pietro Lorenzotti di Brescia (Lorenzotti) based in Brescia.[2] The system was adopted by the Italian Army in 1928, but problems regarding the system began to surface, mainly regarding the questionable lethality of the grenade used; this led to the Tromboncino being declared obsolete and completely retracted from front line service in 1934. The system was replaced by the Brixia Model 35 in this role the next year. The M28 system saw some use during World War II, although it was certainly not used in frontline service.[1] It was most notably used by special forces such as Folgore and the Decima Mas as these units could not carry heavy artillery guns and substituted them with the M28.
After the Tromboncino was decommissioned, many parts of the Tromboncino system were reused for other weapons, with barrels and handguards for the system being used to produce other Carcano rifles. Most notably, the stocks of the rifles used in the system were reused to produce other Carcanos; when the system was discontinued, the stocks of the M91TS rifles were removed from the system, with the mounting inlays used for the Tromboncino system filled up in an elaborate fashion using replacement wood. The stocks were later also reused for the later 7.35mm Carcano M91/38 carbines, with the Tromboncino system intended to be mounted on those rifles; this plan fell through.[2]
Design Details[]
The Tromboncino was a precursor of sorts to the underbarrel grenade launcher of today, and was a rather ingenious design. The Tromboncino was essentially a second Carcano receiver and chamber with a grenade cup attached with space for a second bolt mounted to the right of a Carcano rifle. The system did not come with a second bolt, however; in order to use the Tromboncino attachment, the bolt had to be removed from the rifle and placed inside the receiver of the attachment. Both the launcher and rifle share the same trigger, with a series of linkages inside the rifle controlling the firing mechanism for the Tromboncino.[1]
Of note is that the Tromboncino was designed to not require the use of any special ammunition, permitting use of standard ball ammunition. This is due to the design of the launcher; the inside of the barrel contains a spigot with four vent holes which direct the gas from the cartridge to launch the grenade when the attachment is fired. After the bullet is fired, a retaining cup inside the spigot catches the bullet and holds it securely in place; as the bullet is unable to move, the neck of the case expands and vents gas outwards in a spread around the bullet, which is used to propel the grenade. After firing, the bolt is opened and the case and bullet fall down a cutout at the bottom of the attachment.[1]
Inside the muzzle is a square stem mounted on the retaining cup; the square peg was what the grenade was loaded onto. This stem is threaded and can be removed using a special wrench included with a toolkit that was included with the system; this is stated in the manual of the attachment to ease in the removal of stuck bullets inside the retaining cup.[1]
Ammunition[]
The Tromboncino uses the special S.R.2 bomb, a 38.5mm spigot grenade with an impact fuze. The grenade was sort of a mixture between a fragmentation grenade and a stun grenade; this design was intentional as it allowed its user to fire the system safely in confined spaces. However, this came at a cost of the grenade not being very combat effective.[1][2]
The grenades themselves were fired using live 6.5×52mm Carcano cartridges placed into the system, which would be caught by the retaining cup inside the launcher while the gases from the expanded case neck being redirected around the bullet through four vent holes to fire the grenade.[1]
An inert training grenade was also produced.[2]