Here some Arnold For You :
Minigun
Not much to say, just PVC pipe from different diameter , hot glue and epoxy and voila.
M79 Grenade Launcher
It's always the same : Scaled print out 1:1 , then cut, paint and detailing
Picture shows the M79 on a A4 ( top left )
Bottom Right the scaled print 1:1 ( Half of the gun on 2 A4 )
U clamp used as Trigger guard
Barrel : PVC Tube 40mm
Half painted
Completed M79 with Grenades and Bandolier
The grenades fits exactly in the barrel ( Devil is in the details )
Cardboard Rolls and half ping pong balls
There you have it