Bear with me, as these pictures were taken at different points of construction. Once I make more, I can replace pictures for a clearer writeup.
Disassemble your blaster. DUH. Take out everything.
The middle piece lets the priming rod travel through it, and holds the catch piece. You'll need to shave off the back 1/3 and carve out the front (not shown until later). A [k26] spring should slide in and out easily, if not, file down the passage a little bit.
Put a small length of CPVC in either shell half, in this cavity. These hold the spring rest in place.
Your spring rest is a 1" by 1/2" PVC bushing. The ridge on the inside is large enough to hold the spring, while allowing the plunger rod to travel through. Put a couple screws on either side so that it will "sit" on the ridges, then liberally add plumber's epoxy to secure in place.
I drilled a hole in the catch, and added a length of roofing nail. There's a platform underneath it, sitting on one of the shell ridges. Essentially, a nickel with putty underneath for support. THIS IS ESSENTIAL. You'll need a fairly stiff spring between the nickel and catch; I grabbed one out of a spring assortment box from Home Depot.
Here's the plunger head. I used a 1/4" by 1.5" bolt, with a hex nut securing the assembly on the inside of the 1/2" CPVC cap. I have (2) 1.75" rubber washers from McMaster, some spacers, and 1 1/2" fender washers keeping the plunger head together and making the catch face. Please note that the plunger head is 1/2" longer than pictured here; I had to make adjustments for this prototype.
For the rest of the plunger rod, I cut a notch in the back of some CPVC, and put liberal amounts of plumber's epoxy in to secure the yellow priming bar. Then, to make sure it stayed together, I drilled two holes and used the remainder of that roofing nail as crossbars.
Once you have all that complete, assemble your internals. Use roughly 6" of [k26] spring. Once the rod and spring are in place, put on your plunger head as tight as possible, and screw into place. Cover the screwheads with an epoxy putty ramp, so you can prime the blaster smoothly.
Here's the plunger tube; it's 6" of 2" OD, 1 3/4" ID polycarb. Just slice it up, and use a hacksaw to cut a notch in the back to allow the catch to function properly. Wrap in tape, then place in the translucent plastic sleeve that came with the shell. It'll fit snugly in there; just use some JB Weld or epoxy to hold it in place. There's a 1.5" by 3/4" bushing in the front; the bushings at Home Depot turned out to actually be 1-3/4" in diameter, so some tape wrapping on the pipe and screwing in place was enough for an acceptable seal.
And the final product! It only has about 3" of draw (any more would require cutting into the shell to let the CPVC travel farther), but I'm getting 90+ feet with crappy slugs. I need to lube up the plunger and play with barrels to get optimum ranges, but I'm happy with it!
Edited by Buffdaddy, 14 October 2011 - 08:00 PM.