I used this model: (LINK). Any one will do, as long as you can do the following:
1) NOT A RATCHETING ROD. I'm referring to one that has wedges in the rod for pushing it along. This works differently from the kind posted above, and is not what you want.
2) a rod/plunger head that you can disassemble.
3) While not necessary, being able to disassemble/reverse the trigger mechanism is a big help. Otherwise, you're stuck with reversing the rod, and having little actual support structure for constructing your blaster.
Here's my caulk gun in it's normal state. the plunger head is actually just shy of 2" diameter. Which means 2" PVC might be a possibility....
...oh, look! 2" coupler fits perfectly in the base, and can surround the trigger mechanism! Although I've jumped a few steps. Let's start from the beginning.
Here's me, unscrewing the trigger mechanism. We'll put it on backwards in a bit. Obviously, you should have already taken the plunger head off, or you can't reverse it :-P
Cut a slot here. you need it so that the lever has space to fully extend; otherwise, it won't work properly.
Reassemble in reverse. You now have a shell to put your blaster in....normally. Turns out the way mine was welded, it wasn't straight enough, and keeping the shell would have meant problems with the plunger pressing against one wall of the tube, yada yada. So I ended up removing it, and keeping just the base, for the 2" coupler to sit in.
Chop up a 2" coupler, and a 2" to 1/2" bushing as needed to clear all the space around the mechanism. Has to move freely, you know. And put a short stub of 1/2" PVC. Solvent weld all of that together. Also be sure to JB weld the base, and make it nice and solid.
Take another 2" by 1/2" bushing, remove the lip on the inside so it can slide over the 1/2" PVC. Then put a coupler on the pipe. Apply adhesive as necessary to hold things together. Note that you can still slide it off.
Now for the plunger head. In hindsight, I should have kept the normal orientation, put the skirt seal behind that, and a polycarb cirlce behind that. Would have made it still capable of disassembly. Also, I SHOULD HAVE PUT THE SPRING ON FIRST. A [k26] is a bitch to wind around a 5/16" steel rod. Anyhow, the spring will sit in the coupler at the base just fine.
I cut a 1 7/8" polycarb circle, with a 5/16" hole in the middle. I put the skirt in the middle, and then JB welded the polycarb and metal together. The skirt is still free to move a bit; I put a 1/4" sliver of thinwall 1 1/4" PVC inside it for spacing it properly. Clamp together, and let cure.
Put on a 10" length of 2" PVC for your barrel, then cap it. Drill a hole for airflow, then take a 1/2" bushing of some kind and cut the pipe end down until flat. Weld together and cure.
Not pictured, but necessary: use screws to hold the plunger tube together, so you can disassemble as needed.
Make sure you're lubed up, and you're ready to go. Initial testing had me hitting 100' easily, although I should note the only availabe barrel at the time was 22" of CPVC. Obviously too much. I'll have more testing and video later.
Q: How do you prime it?
A: You pull back the rod. Or use the lever, if you're a weakling. lol
Q: How does it fire?
A: The metal plate in the trigger position exerts severe friction on the steel rod in one direction. This allows full spring compression. By pressing it, you release the rod and fire, just like on an Ultimator or XXL Bazooka.
Q: I don't like the giant hook in the back, waiting to diddle my face. Anything I can do?
A: Sure thing, you can always build a shield for your face.
Q: I don't want a pullback blaster...
A: Then make it pump action. Dear lord, do I have to do everything for you?
Edited by Buffdaddy, 20 August 2011 - 11:06 PM.