The original plan was to make a homemade plunger tube/rod/head, but I had a spare Nitefinder sitting around so I just raided that. The first step, after opening the Gotcha Shot, was to clear out all the junk inside. Everything except the catch, spring, and trigger went straight into the garbage. Fortunately, the catch isn't actually attached to anything, so you don't even have to cut it off.
Next break out the dremel! I highly recommend getting a "high speed cutting" bit, it's all I use anymore.
Everything that holds the original internals should be cleared away, except for the rearmost wall. It's a convenient brace for the Nitefinder plunger tube. This is where I made the biggest mistake of this mod. The rectangle that is cut away from the shell was raised up and flat, from eyeballing the plunger tube fit it looked like it had to go. When I finished both sides and put it together, the plunger tube was loose and rattling around. Fortunately the problem was easily solved with a few layers of electrical tape, but the moral of the story is that cutting twice and measuring once is completely wrong!
Look at that plunger rod action!
The pump length on the Gotcha Shot is about 3 inches, but the Nitefinder rod is just long enough to cover it. I ended up cutting it under a 1/4 inch from the priming handle, but you'll want the rod to be as long as possible and trim it down to fit. Make sure to trim down the Nitefinder catch as well, so it doesn't get hung up on that bracing wall. Then use goop to attach the rod to the catch. I just measured the draw of a stock Nitefinder, and was surprised to find that it is apparently only 1.75 inches, so there's definitely an air volume increase. The spring is also stronger then a stock Nitefinder spring, I don't have any of the popular replacements to compare it to though.
Now it's time to get the tube in there!
It's so close to being a perfect fit length-wise. At first I just trimmed the tiniest bit off the back end, under an 1/8th of an inch. When it became apparent that it was too loose to just sit in the shell, I got out the Gotcha Shot's original "barrel" to stabilize it in front. The plunger tube won't fit inside the barrel, but it's close enough that you can widen the inside of the barrel without cutting through. Goop them together, wrap e-tape to stabilize the back, and it sits in there quite solidly.
Looking good so far!
It's a half cpvc 1/2 inch coupler, gooped into the hollowed out thing that holds the Nitefinders A/R, which is gooped to the plunger tube and Gotcha Shot "barrel". Although I did this last, I would recommend doing it before trimming the plunger tube. When I fit it on the plunger tube normally, it was too far in and the plunger head knocked it off after a couple of test shots. In the picture it is attached a little bit further out, but is holding together so far. It is completely airtight, when I hold my hand over the coupler the plunger stops with about 1/3 of the tube left.
All together now!
The finished product. It shoots across my living room and into the hallway wall without losing any height. I think that's something like 35-40 feet. An outdoors test doesn't really matter at this point, since it's below freezing with a couple feet of snow on the ground, but it should get comparable ranges to any draw-extended Nitefinder. It's a really comfortable and cool looking shell, I wish I hadn't cut those rectangles out of it though.
I'd like to set up a breech that opens when the pump moves back and closes when it moves forwards again, but I'm not sure how to do it without adding a ton of dead space. Do breeches still work if you push the dart behind the opening instead of in front of it?
Anyways, that's all for now. Hope you guys enjoy the mod/writeup, I was just glad to find a project that interested me over the winter here.
↓ Haha. Yeah, I scraped off the "DO NOT" part.
Edited by VelveetaAvenger, 25 January 2011 - 04:48 PM.