This Sniper Rifle reassembles the 25 mm Sniper Rifle by irWinner, which i give all the credit in the world to, except the barrel size and a few corners i cut =]

Major credit to everyone at spudfiles.com who helped me fix my sprinkler valve problem.
18in. Barrel

Modded Sprinkler Valve trigger
bike pump powered (easier for the most part)
Battle-Rifle type feel
Quick-load slide

No video yet >.< but I'll upload one as soon as I fix a leak in the bike valve and get the time to video it

Step 1: Materials:

I can't stress this enough

a rainbird or watermaster sprinkler valve.
apparently any other kind won't work because of a guide rod inside the others.
I bought one and I had to get the other watermaster 3/4

Good amount of
3/4in. piping
1in. piping
a 1ft. piece of 2in. piping
(all sch 40)

Main Body:
tire valve
2in. end cap
2in. coupling
2in. to 1in. reducing bushing
90 degree 1in elbow (2)
1in. Tee elbow
1in. to 3/4 threaded reducing bushing
small piece of threaded 3/4 on both sides to connect the sprinkler valve to the rest of the gun
3/4in. to 1/2in. reducing bushing (for barrel)
1/2in threaded piping (18in. long)

Stock:
1in. coupling
1in. to 3/4in. reducing bushing
Tee elbow 3/4 in.
3/4in. 90 degree elbow (2)
3/4in. 45 degree elbow (2)

Other:
1/4in. barbs to connect sprinkler valve to blowgun
blowgun
pressure rated hose
Teflon tape
PVC cement
PVC primer

Recommeded:
Paper towels
wrench (to tighten barb into valve and other jobs)
drill
drill bits (assorted)
bike pump w/ gauge
scope (not necessary)
laser (not necessary)
JB weld or hot glue
epoxy putty (to plug up the solonoid hole
working area (the primer is VERY messy)
Hacksaw (any saw)
sharpie
tape measure
Dremel

Step 2: Stock

To start with, most of this does replicate the 25mm sniper rifle, however this stock isn't blocked off, therefore it adds to the size of compression. I didn't see any benefits in this but it was easier in my point of view. Make sure you cut these right, i actually had the side facing in a little shorter, and it makes me feel horrible because now it's not completely straight. I hope to make a brace to straighten it soon.

Just cut pieces of 3/4in piping to put in between the elbows and the Tee connects it. It really depends on what you like and the size you choose.

Step 3: Chamber

cut a 1ft. piece of your 2in. piping and grab your 2in coupling, 2in end cap, and 2in to 1in reducing bushing. drill a hole in the center of the end cap (1/2in hole). The tire valve should fit about halfway through. This is the hard part, gluing it in place. I've found hot glue seems to hold it, i tried JB Weld in this instructable. You can either cement all of this now or glue it all at once like I did.

Step 4: Modded 90 Degree Elbow

Grab your dremel ( or other cutting device that I really don't recommend) and the 90 degree elbow 1in. Cut the 'back" out of the elbow, so a solid piece can slip right through it and connect to the rest of the body.

Make sure you shave out the inside of the elbow or the pipe will get caught.

Step 5: Main Central Body

Cut about a 3in piece of the 1in piping to put in between the non modded 1in elbow and the Tee 1in thing. cut another piece a little shorter for the piece to the reducing bushing of 1in to 3/4in threaded. Now, you can now cement everything in place, but I recommend not cementing the 1in to 3/4in threaded adapter until you mod the sprinkler valve.

Step 6: Add the Stock to the Main Body

Self explanatory

just glue the stock, chamber, and connecting body together.

Step 7: Mod Your Valve

Now, you can mod your sprinkler valve

Get either a rainbird or a watermaster, apparently nothing else works because of a guide rod.

Here's the youtube video for the mod that I used:

Step 8: Mod Your Trigger Housing

grab a 2in or piece of 3/4 piping and your Dremel

Cut (see picture) the piece to hold the blowgun and cut a hole in the 45 degree elbow (3/4in.) to feed the tubing inside.

Now glue the 3/4 45 degree elbow into the modded piece, and for me I glued the 3/4 elbow directly into the 1in previously modded 1in. elbow.

again i replicated this from the 25mm sniper so that instructable will help as well

Step 9: Barrel

This is also an optional step that should decrease performance slightly but make life a little easier

I had a 1/2 in. pipe about 18. in long for the barrel threaded, and i found that 3/4 sch 40 pipe would fit perfectly if dremeled inside

this took me quite a while to dremel out, i dremeled a little and tried to fit it into the pipe over and over so this may be more work than you would like.

next, just use a cutting piece of your dremel to cut about half of the top of the barrel.

Step 10: Finishing Touches

Add a scope if needed, for me, I have a laser from dragonlasers.com that I will attach.
I didn't attach it mainly because i would duct tape it on (so I could take it off when i wanted to) which would make it look unrefined
Feed the tubing from the sprinkler valve into the blowgun, pressurize, and test it.

I've found that the best ammo is either nerf darts (the orange tipped whistle ones fit perfectly), AA batteries that are dead, airsoft BB's for that shotgun effect, or Paper Darts by barri_kid