Available in both rifle and pistol flavors as well as an actual full-auto submachine gun for the .gov types, the Vigilance Rifles M20 series is here. This line of 9mm NATO, side-charging guns offers quick change barrels and a tilt-up machine gun-style top lid for accessing the bolt and recoil system.
On that machine gun lid are integrated front and rear sights along with a Picatinny rail for optics mounting.
The slab-sided M20 is stated to accept PROMAG magazines, though it appears to be a GLOCK-spec magazine footprint. Looks like AR-15 grips and triggers are used, too.
The exposed barrel nut allows for quick barrel swaps.
Nice to know it’s “Considered Military Spec.” MSRP starts at $1,699 plus shipping.