I googled "Star Wars EMP grenade" and came across this picture:
I am not sure if it is actually from anything Star Wars-related, as the image was on a non-Star Wars website, but I liked it and decided to use it as the inspiration for my own EMP grenades.
The components I used for this were:
a) (1) 1" compression coupling (approx $6.00)
b) (7) 2" x 3"16" o-rings ($0.99 ea.)
c) (2) black plastic end caps ($0.35 ea.)
d) (2) red plastic end caps ($1.25 for a bag of 25)
Once I disassembled the compression coupling, I discarded the o-rings and plastic rings that came with it, as they would not be visible in the finished product, but they could certainly be left in.
There is minimal sanding needed to remove lettering along the outer edges of the end caps. I left the lettering along the shaft as that area will be entirely covered.
Next I primed and painted the coupling pieces metallic silver:
These are the only parts I painted, as I wanted the metal washer piece to retain its metallic-ness and stand out against the painted metallic color.
I added a thin layer of foam around the shaft to even out the ridges of the coupling and to add a little extra thickness so the o-rings wouldn't be loose. Then the o-rings were installed:
Next I sanded the paint off the ends of the internal pipe and glued on the end caps. First the black ones, which sit nicely inside the interal pipe, and then the red ones on top of those:
Next, I sanded down the edges of the end caps and glued the metal washers to them:
Finally, the end caps are screweb back onto the main body:
As a final touch I used transparent black paint to weather a couple of the grenades I made. The following picture shows two freshly finished (left) and two weathered (right):
