Image: Bend Studio / PlayStationOfficial screenshot from Bend Studio / PlayStation.
The RPD is a Military Spec Russian light machine gun with a 65-round drum. The in-game description pitches it for Horde fights, and it delivers. It is also your starting LMG in challenge-mode Horde fights.
It holds a chokepoint against a Horde and keeps camp defenders pinned. Fire in bursts to keep the drum on target.
It beats the MG45 on condition and drum size. The MG55 from Horde Killer has lower recoil and a 75-round belt. Move to the MG55 once you have it.
Chicago Chopper
The Chicago Chopper is a drum-fed Military Spec submachine gun sold at Wizard Island from Trust level 2. It has the highest fire rate and a 55-round drum. It is a primary-slot answer to Freaker crowds at close range.
M50 Reising
The M50 Reising is a Military Spec submachine gun sold at Lost Lake from Trust level 2. It fires fast and stays accurate at range, but hits light. An upgrade doubles its 15-round magazine to 30.
MG45
The MG45 is a German-made light machine gun for the special slot. It has an extremely high rate of fire, which makes it hard to aim at range. The Hot Springs merchant sells a belt upgrade from 55 to 95 rounds.
MG55
The MG55 is a Special Forces medium machine gun with very low recoil. It unlocks free at 60% of Horde Killer and goes in the special slot. It is the best machine gun for taking a Horde apart.