Background info:
The original idea for this came from the Titan. I am going to make a pseudo-replica/approximation of an M16 w/ M203 grenade launcher from an LS and a Titan airtank. I wanted the LS to have a shotgun priming mechanism and the Titan to fire at least five barrels in a shotgun blast. This was impossible to do with the Titan because it is so big around. In order to use the Titan, I would have to make the shotgun grip for the LS out of like 4" PVC. That would look/feel awkward, so I kept thinking on it, and I started thinking about using an AT2K tank. The problem with the AT2K is that it wouldn't be able to fire multiple darts very far at all. That's when I decided that a new type of tank expansion was needed. I needed the power of a Titan in the diameter of an AT2K.
While browsing around the hardware store looking to find pipe that would fit together well in order to make the launcher, I found some sch. 80 PVC nipples. the fit around the AT2K tank was absolutely perfect. It wasn't so tight as to require a lot of effort to put in, but it wasn't so loose as to easily fall out. I also found that if the sch. 80 was ground down a bit, it would fit perfectly inside 1 1/2" sch. 40 PVC. I also knew that 2" PVC would fit nicely over the 1 1/2" PVC, so I could use it for the shotgun grip.
I also like the idea of having "grenade shells", so I am going to make interchangeable shells that have three barrels each, and each barrel is loaded with two darts. I will explain this more later when I finish the entire LS.
The instructions begin here
To start building the tank, you have to cut the AT2K tank in half, and leave an equal length of the 1 1/4" diameter part of the tank on each side. This will give enough room to make sure the adhesive holds on tight to prevent blowouts and leaks. The next thing to do was find a longer firing pin. I came to the conclusion that 3/32" rod was the best size to use since it was ever so slightly larger than the original firing pin. I had trouble finding something that size until I found the K&S brass section of my ACE store. They had 3/32" rod, which fit perfect in the tank. Next, you need a longer spring. I got the spring from ACE as well. I got a...#184, I believe. It is only about 3" long though, so it needed to be stretched, but to keep it from shrinking, it must be heated at 500 degrees in the oven. I heated mine for 10 minutes or so, and it has held its length through over 50 firing tests, so I don't see it shrinking. You also need to drill out the two white pieces inside the tank. One holds the o-ring in place and the other has the rubber seal attached to it. Drill both of them out just big enough that the 3/32" rod can be easily slid through. I also made an "O" shape on the end of the rod to use as a trigger. This isn't necessary, but it works nicely for my intentions. Now onto assembly.
First, glue the front of the tank into one end of the nipple. Next, put the firing pin through the back of the tank, then put on the o-ring, then put the back white piece on, then add the spring and then finally push the piece with the seal on it over the firing pin, and glue it into place. Once the back half is assembled, push it into the back of the nipple and glue into place. Note that if you pre-bend a trigger out of the brass rod, make sure the rod stays long enough to seal the tank once everything is together. Now you just need to add some tubing and a pump.
Onto ranges:
Right now I am using a Titan pump, and I pump it 15 times. I haven't range tested a singled barrel, but it fires insanely fast. I did measure ranges with the triple barrel, and I am very pleased. With the six darts loaded, they average about 50'-60' each with 6" PETG barrels. The lowest range from any single dart was 49' and the longest range (which was actually three darts that landed fairly close together) was 80'. These are measured ranges and not estimates. They were fired flat from slightly below my shoulder, and I am 6' 4" tall. Also make sure to use fishin' glue to adhere these things. DO NOT USE AMAZING GOOP!!! That stuff isn't amazing at all. I also mis-interpreted what it was for. It is not an adhesive, and even after curing for two days, the tank blew out after like 10 pumps. I used JB Weld on the back half of this with no trouble, but I had leaking issues with the front when I used it, so I used lots of Fishin' Glue instead, and it sealed up great. I don't have any leaks anywhere.
Here a pics of the barrel setup (until I make the shells) and a size comparison with my NF2K and a Titan airtank:
Questions? Comments?
