I'm not sure if this will work with the old zappers, i think their inner workings are diffrent then these new ones, but here is what i started with.
and this the the gutted gun who donated it's internals, i got it for $2 at walgreens.
Start by gutting the zapper and sanding down the inside the barrel, then try setting the internals in the gun to get an idea of where you need to place them,
cut the plunger rod off just a little past where it comes out, then drill a hole in it, so after you cut down the cord, you can tie it on.
You'll need to cut off the center screew post on the green outer shell to make room for everything to sit down in there, you'll have to sand down the side of the front green post too. When you know where the internals will be sitting, you need a front stop for the tube, i used the little orange peice from the front of the starting gun. You'll also need to build a back plate for the spring and a channel to house the spring catch(i just used plastic i riped off on the starting gun) and on the other side of the main body you will need to line up a peice of plastic to make sure the catch stays down, it should be just as tall as that half of the shell. Also when you are gutting the zapper, make sure to keep the part that goes behind the trigger, you'll keep that same sound when you pull the trigger and it will act as a spring
You need to sand down the sides of the tube and the top of the little wheel you'll use to redrict the cord to come out at the bottem(I distroyed my double shot some time ago and now it's sitting in peices, but i found the little wheels in that work perfectly)
last thing to do is building up the trigger, this was kind of an odd step where you need to figure out where you need to build upto so it will push on the spring catch.
Then all that's left is to put everything together.
I hope you enjoyed this and that it helps.
