Italy adopted the Villar Perosa in 1915, a gun that is sometimes considered the first submachine gun. Despite being fully automatic and chambered for pistol ammo (9mm Glisenti/Parabellum), it was actually not a submachine gun in practice. It was actually a twin gun, fired usually from a bipod using spade grips. It had some very specific applications, but was generally not very useful, and Italy set about looking for alternative uses for them. The solution they found was to split the guns into single receivers and fit them with buttstocks and traditional triggers. This led to the first true Italian submachine gun – the OVP-1918 – and also the Beretta 1918, which was originally a semiauto-only carbine.
The Beretta was made using Villar Perosa magazines, magazine latches, receivers, and bolt assemblies. The stocks came from Vetterli rifles and the bayonets from Carcano carbines. Only a few parts like the trigger assembly and ejection port housing were made from scratch. Beretta was given a contract late in the war to convert 5,000 Villar Perosas into these carbines, but was unable to complete the work before the war ended and the contract was cancelled. Of the guns that were completed, many were later converted into Beretta M1918/30 carbines and others were sold as surplus. A bunch of them went to Ethiopia, where some were ironically recaptured by Italian forces in the 1930s and put back into service in World War Two in North Africa. This example is one of a few recently found intact in Ethiopia.
Villar Perosa: https://youtu.be/NAsH0fVAoxc
Shooting the Villar Perosa: https://youtu.be/WLFA8VXVkRQ
OVP-1918: https://youtu.be/K2nhwH1I8PU
Beretta M1918/30: https://youtu.be/jNrAsnfI5-k
The ejection tube is likely there to avoid the shooter to cover the ejection port with his hand.
Maybe that’s not why it had been done that way but, being the sights on the right side, a right handed shooter, as long as he keeps both eyes open, has not his field of vision limited by the magazine.