It is assumed at the beginning of this mod that the crossbow has been opened, the yellow tube and barrel has been taken out, and the necessary plastic has been removed from the case to allow a barrel to come out of the front. Once you've got that down, then you can begin:
The first part of the mod I'm going to explain is for the pre-barrel piece that your barrel will connect to. To make this is pretty simple, take a 3" piece of sch. 80 1/2" PVC, and put a 1/2" PVC connector on each end. (One of my connectors is taped black for looks) then, use epoxy or plumbers goop to attach the coupler to the yellow plunger tube. Before I did this, I cut the nozzle off, and widened the hole the air is pushed out of, but I've found no difference in performance with or without it. Make sure that the coupler is glued in the very center of the plunger tube, and is flush with the surface. If it's off, it will affect where your gun aims.
The second thing that needs to be done is to reinforce the plunger shaft. These things are way too weak, and will eventually crack if you replace the spring or band it, maybe even if you don't. What I did was to plumbers goop in a metal rod at the notch in the shaft (one on each side). Then, to keep that piece from pivoting I gooped-in another rod above it and behind the notch-wall. It really doesn't matter what sort of rod you use, whether you go out and buy steel rod, or just cut the head off of a nail. Make sure that if any goop protrudes out from the width of the rod, you sand it off when the shaft is dry. Otherwise your plunger will stick when you pull back, and also when you fire. To increase plunger efficiency, I used some lightweight masking tape around the rubber plunger head to make it wider. I also applied graphite lubricant to the inside wall of the yellow plunger tube.
If you want your crossbow to stand the strength of a new spring, or even banding, you're going to have to re-enforce the compression wall for the spring. To do this, I put two bolts into the two main pillars on each side of this wall. Make sure you use washers on the outside of the case so you don't crack your gun. Also to avoid this, drill pilot holes of a slightly smaller diameter before putting the bolts in. Even with these bolts in place, the wall is still going to need more re-enforcement. I decided to go with steel plating and plumbers goop. I gooped-on four small steel plates, one for the bottom width of the wall, one for each pillar face, and one behind. The first three mentioned are gooped on flush with the surface, while the fourth one was gooped at a 45 degree angle on the back side of the spring-wall. (triangles are your best friend in the engineering world).
One thing that is annoying about the crossbow is that to fully pull the trigger, you basically have to push the trigger completely flush with the casing. My trigger finger always hurts after big wars. To fix this, I figured there were two options: add on to the trigger where it contacts your finger, or heighten the triangle on the top of the trigger piece. I chose the latter. To accomplish this, I cut two triangle pieces of the same steel plate I used above, and plumber's gooped them onto the trigger. One very important thing about this process is that you have to keep clear the slide and rail system for the trigger. In other words, if you glue your triangles too low, your trigger wont fit back into your gun.
Once all of this is done, the gun can be put back together. You may notice that in my pictures there is no spring in the gun. The reason for this is that I accidentally broke my replacement spring, and refuse to use the original spring. I figured having a spring in the pictures weren't worth the extra time it would take me to get another. Another thing that you'll notice is that almost every crevise in my gun is filled with foam. I was annoyed when my ears rang after every shot, so I quieted up the gun a little by adding the foam. The foam above the yellow tube is backer rod, and the foam below is foam insulation for 1/2"-3/4" piping. The foam in the handle is just flat chunks of foam from the insulator. The important piece of foam is the one that goes over part of the front-most PVC coupler. This is a piece of the insulation foam I just mentioned, but it has been slit, and also cut into so that the screw ports aren't impeded. This foam keeps my barrel steady in the case.
Your gun is now ready, but you'll need a barrel. Because of the 1/2" coupler, you'll be able to put on any variety of barrels via 1/2" PVC. The barrel that I chose to use, because it suits my darts the best is a 3 sectioned telescoping brass barrel. To make the barrel, take 10" of 1/2" sch. 80 PVC, place inside of that 12" of 9/16" inch brass. The brass should stick 3 inches out of the back (the distance from coupler to coupler, not a coincidence) inside of the 12" brass section is a 6" piece of 17/32" brass. This should stick out the back of the 9/16" about 1/8" of an inch, as little as possible.
That about wraps things up now all you have to do is make Stefans that fly straight, and people will swear that Satan resides in your gun. If there is anything that doesn't make sense, contact me. I'm sorry the pictures are quite the sux0r, I hope the writing was descriptive enough. Once I get my new spring, I'll put up the correct model number, and the length it should be cut to. I'll also try to get around to measuring it officially. It can hit a moving target at 70' no problem, YANO participants can vouch for that.
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