[quote=@Senhara]
Oh I'm more saying like a traditional firearm. Telescoping ammo has the propellant encase the projectile in some way, resulting in better barrel velocity for the same cartridge size when designed right, I'm more concerned about fielding such a weapon with insane RPM
[/quote]

Yeah - I think the Autocannon with the Munitions Pack synergy upgrade describes what you want to go for pretty closely. Again, you can flavour the specifics how you please since there's lots of different autocannon models and what's presented is more an umbrella term describing the general idea.