I used a set of spare grips from one of
my Browning M1919 patterns, and made some nice oak grips from
1-1/8 diameter dowel from the local hardware store.

This barrel pack is based on my
Honeycomb style layout, and are identical to the one's on
the 2010 Give-away gun.

The main body tube is 2 inside diameter
ABS plumbing pipe, the motor is 1-1/2 inside diameter
stuff. Large zinc-plated washers adorn the grip mounts. Notice
the big wing nut inside the tube facing you here. Un-do it,
and the gun can be lifted right out of its
mountings.
This was a non-functional model, built to
explore the possiblities of the Small Minigun
Patterns.
A Thompson M1A1 provides a sense of scale
that the grips don't: this is a very small
item.