Vacuum Loading Tagger Shotgun

Blaster Design and Instructions by KaneTheMediocre

Forum Threads:

http://nerfhaven.com/forums/index.php?showtopic=18963&st=0&p=266830&fromsearch=1&#entry266830

http://www.nerfrevolution.com/forums/viewtopic.php?f=9&t=871

A dick-waving video showing a few HAMPs, including both the VLTS and the BATS, can be found here:

http://www.youtube.com/watch?v=FRpDRu3WEoc

Construction:

CAUTION:  It is very important to thoroughly deburr the sharp edges that result from cutting these parts, and even more important to clear all of the chips away.  For the steel EMT, that means at the very least blowing / pushing some wet toilet paper through the barrel, repeatedly, from both sides.  You don’t (or you shouldn’t) want to be shooting metal chips along with your darts.

1. The Elbow:  There are lots of ways to do this, the easiest of which uses a 1/2” piece of braided tubing.  The method described here is much more difficult, but improves airflow a great deal (1/2” braided tubing has about ¼” ID).  Another method, which has good airflow (but not quite as good as below) starts with a ½” hole, and nests PEX in CPVC, and CPVC in PVC.  Most hardware stores carry impact coupling tools to achieve this:

The PEX-CPVC-PVC method only requires a 1/2" hole, which is usually easier to make cleanly.  The disadvantage is slightly reduced airflow, more gap between the barrel and the HAMP, and lots of quality time with the hammer.

1a. Drill a 5/8” hole in your HAMP, a close to the plugged end as you can put it without damaging the end cap.  This is not a terribly easy task, as drills will get often get stuck and stall out frequently, or they might quickly and unexpectedly make a triangular hole. 

A drill press and / or a good clamping system is very helpful for getting the hole to start on the curved surface.   Beware that a powerful drill may grab the piece and pull it out of your hands or clamp, spinning it until it hits the post of the drill press our your face.  With patience and/or frustration, and a wee bit of scissor work at times, it can be done with a hand drill.

1b. Insert a small piece of CPVC and the CPVC elbow into the hole, and put the PVC coupler on the CPVC elbow (the elbow fits loosely inside the coupler).

1c. Affix these parts.  Since my hole looks like it was made by a 3rd grader with an icepick, I used plumbers putty / epoxy putty, which smells bad, takes time to set, and gets on your fingers.  

I have no doubt that this could be accomplished as well by some choice or combination, of duct tape, hot glue, e-tape, and/or ticky tack.  Ticky tack is the best for making a good seal, but doesn’t provide any useful mechanical bond.  This can be fixed by adding duct tape, which is mechanically great, but doesn’t make very good seals.  Hot glue is good if you want to make a messy clusterfuck that seals great until you use it on a hot day.  Or a cold day.  Or you drop it.  Just make sure it’s at least sort of airtight and stays on to your satisfaction.  Don’t feel like you need to stick with my methods in part 1; I know I haven’t. 

2.  Cut off 3’ of 1/2” EMT Steel Electrical Conduit for the barrel.  You can use ½” PVC for the barrel.  In fact, this slight tighter fit will often get better range, but it will jam occasionally, and require some unpredictable amount of notably obscene finagling to extract the dart.

5. Attaching the barrel:  This step is MUCH easier if you use hose instead of an elbow in part 1, since you don’t have to space out the barrel to compensate for the elbow height.  

5a. Use a small piece of thinwall ½” PVC to mate the barrel with to the PVC coupler.  Duct tape or E-tape could be used instead if need be.  Superglue the thinwall PVC on to the end, to keep the barrel from sliding into the coupler.

5b.  Stick the barrel into the coupler, and put something between the HAMP and the barrel to compensate for the elbow height, then tape it down to the HAMP.  I used a 1/2” square wooden stick, but a mess of cardboard and duct tape works alright too.  Do everything you can to keep the barrel and the HAMP parallel.  

If you used a hose in step 1, there’s no gap to space out and you can just tape down the barrel.  If you’re making a BATS, you need to make sure that your spacer and whatnot do not interfere with the action of the breech.  I didn’t have to worry about this much with the ½” square wood, but with a mess of duct tape, you might be limited to attaching at the front and rear of the HAMP, leaving the middle (where the breech travel lay) open.  Also, if you want to try gluing the barrel, that’ll probably work fine, and in fact will better keep the barrel from moving sideways once dry.  I’m a duct tape man, and so that’s what I use.

6.  Put a screw in the very rear of the barrel, to prevent darts from being sucked back into the gun.  This wouldn’t hurt for a BATS, but normally the bolt-pin takes care of this.

7. The Plunger Guide:  HAMP plungers seal best when the plunger is close to coaxial with the casing, and for practical use, you don’t want to be able to pull the plunger off the gun, or hit the air exit tube on the inside.

7a. Position the plunger in the HAMP so it’s about ½” away from hitting the air exit tube. 

7b. Find something that slides nicely on the barrel.  I used ¾” PVC for this, but in the past I’ve used ¾” EMT, rolled up cardboard with duct tape, etc.  It’s not critical.  Put it on the barrel.

7c. Find something to space out the barrel.  I used the same ½” square wooden material as the barrel spacer, but I needed to wrap it in duct tape to pad it out a bit.  Again, cardboard/newspaper/whatever is fine, it just needs to take up space

7d. Tape it all together.

I avoided taping all the way around here, because I wanted a good sliding surface to present to the magazine, but usually I go all the way around, and it’s not really a problem.  In retrospect I wish I’d gone all the way around, as it would add a lot of strength.  It seems to hold up all right as it is, but I suspect I’ll break it at a war and end up retaping all the way around anyways.  Also, there’s a bit of extra plunger length past the spacer/plunger guide, which I ended up cutting off later.

7e. To avoid pulling the plunger out of the gun, you need to make an out limit stop.  This can be done easily by pulling the plunger out as far as you want it to go, then winding duct tape around the barrel at that spot.  Don’t let any yarn show, as entering/exiting the tube can scrape it along the inner edge of the outer HAMP tube, and damage the plunger. 

8. The barrel tip:  I used ¾” PVC for this, although I’ve used thinwall 1/2” in the past.  I strongly recommend 3/4” PVC, as it provides a very blunt tip, which is better for safety in case you accidentally bump someone (No one wants to get stabbed with EMT).  It’s also crucial if you want to barrel tap, although from both a safety and gameplay perspective, barrel tapping may be the most idiotic rule ever to be put forth for nerf warfare.  But that’s another discussion.  Anyways:

8a. Make sure your out limit stop is wound to close to the OD of the barrel tip.

8b. Wind more duct tape around the barrel, to the ID of the barrel tip.  If you have much barrel left (as I did), you may need to do this in 2 places.

8c. Cut off some 3/4” PVC, about 1/2” longer than the amount of barrel you have left, and slide it over the barrel.  It shouldn’t wiggle too much with the duct tape spacing it out inside.  Tape it on, winding duct tape around the crack between the out limit and the barrel tip

8d. Make the tip orange.  This step is not optional.  I don’t care if the whole thing is spraypainted purple, do not underestimate the imagination of a policeman.  I use orange duct tape, but you could paint it if you like.  I’d recommend painting the tip prior to attaching it, if you’re going that route.