An upgraded/higher tier smg, inspired by the Italian Villar Perosa 1915, from ww1.
Would have a capacity of 50 rounds, 25 per gun, a very high fire rate, a very short reload time, and would either use the already existing smg ammo or a new smg ammo designed specifically for it.
Irl it was nicknamed the Raspberry, presumably because of the sound.
A possible in game name for the gun could be the “Cicada”, named after the extremely loud flying insect.
Link to the Wikipedia article on The Villar Perosa 1915:
https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://en.wikipedia.org/wiki/Villar_Perosa_aircraft_submachine_gun&ved=2ahUKEwjpu8OYqvOMAxWiWkEAHRXyKvgQFnoECBoQAQ&usg=AOvVaw3bwz0z8IyupgiBsgSt8Gsb
And an image from wikipedia:

How about adding actual cicadas (the bug) to the game as well? Hmmm?? How about that??? I think that would be a better development