Picture of Rocket or Grenade Launcher Pistol


UPDATE: This thing has a very short range. If you build this, you would be lucky to get 150 feet. I have since taken it apart and rebuilt it with a 24 inch barrel.

Cost to make - roughly $15 plus cost of Mad Bull XM PB4 unit.

My cost to make - $3. I had almost everything I needed already.

The Mad Bull XM PB4 is a Rerservoir and Valve system for pressurized volatile liquid. For airsoft, this liquid is called Green Gas. When the Valve of the PB4 is triggered (opened) all the liquid flows out of the reservoir into the Chamber behind the Nerf Football. The liquid - being very volatile - QUICKLY vaporizes into a gas state. The volume of the Gas is hundreds of times Larger than the volume of the liquid state. This Rapid Expansion from liquid to gas is what Pushes the Nerf Football out of the launcher. For further explanation, please talk to your local high school science teacher.

UPDATE: I took this launcher apart and built a longer launcher. The new launcher is 24 inches long. It is a compromise between the pistol and the LAW which extends to 30 inches long. It abandoned this design because the range sucked.

Step 1: Tools and Materials


Dremel / Rotary tool with the following attachments
- Cut off wheel
- sanding drum
- shaper / cutters
Drill with assorted drill bit
Screw tap
scroll saw
hack saw
screw driver
Clamp (optional)

ABS or PVC Pipe 2" schedule 40
Shielded pipe coupler (see my M72 Law instructable).
aluminum bar
steel rod

Mad Bull XM PB4 airsoft grenade (also sold by RAP4).

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jgderuvo4 years ago
That's sweet!
malumalu5 years ago
where can you buy the madbull xm pb4 round?
airsoft websites like evike but they are 40-60 dollars each.
could u buy an empty used on on ebay? or a new one on amazon
MrTinkerer (author)  pieman125 years ago
an empty used what?
MrTinkerer (author)  pieman125 years ago
All grenades are sold empty.
thanks im kinda new to airsoft and i thot making this would be cool
can i buy one off of you? i will pay more than the original cost to make, plus shipping.
MrTinkerer (author)  heavymetalman15 years ago
It's not so much the cost of the materials that will get you as it is the cost of my hourly rate. I think 4 hours labor time is a fair estimate...
sbann55 years ago
how far dose it go ???
MrTinkerer (author)  sbann55 years ago
Not very far. About 100 ft. It sucks.

I scrapped the design and built one with a 24 inch barrel. The new design is now a shoulder fired launcher with a max range probably a little over 100 YARDS.
 how did you connect the hinge to the activation lever? or what sort of screws? and, did you just put the other end of the hinge under the metal part of the coupler? thnx
MrTinkerer (author)  mazingbrainiac5 years ago
The hinge is attached to the aluminum bar using the screws that came with the hinge. The other end of the hinge is just tucked under the metal binding strap of the coupler.
is there any way to take the grenade out? i plan on using it for airsoft and i would need to reload it. also will this work with any m203 40mm round?
MrTinkerer (author)  bdogjhonson15 years ago
I play airsoft too. The reason why i built this is because I neededsomething to give me that added edge on the airsoft field. I haveairsoft in mind when I build all my launchers.

Look at the current launchers in the market that use the 40mm grenades(example, Deep Fire M72). They require you to unscrew the back and plopin another grenade with a fresh charge of green gas. Well, if youhave to have multiple grenades at $40 a pop, that gets expensive fast.

Well, you say, "y not just one grenade, and keep refillingit?"

Hmmm, that goes something like this : FIRE > unscrew back >extract 40mm grenade > fill > replace grenade > screwback on > FIRE. Sounds like a lot of steps, right?

My Launcher goes  FIRE > refill grenade> FIRE!

which looks faster?

The short answer - No, you do not want to remove the grenade.
would it b ok to have the wood screws come down from the pvc pipe into the handle? because i'm using sorta old wooden saw handle. its in great condition, but it isn't long int he front or the back for wood screws like yours. any ideas?
MrTinkerer (author)  mazingbrainiac6 years ago
I used wood screws too on my first build. I put the pistol grip on and marked how far in the screws went into the tube. I then removed the screws and cut them down so they were flush inside the tube. It was still rough and probably snagged the fins of the nerf football. Than is why I abandoned the screws and just used epoxy and bondo to hold the pistol grip to the tube.
so u basically glued it on? with epoxy and, bondo? aight thanks
MrTinkerer (author)  mazingbrainiac5 years ago
be sure to sand the tube so the epoxy and the bondo has something to stick to. Use 60 grit sand paper.
is there a spring somewhere to keep the trigger from staying depressed?
MrTinkerer (author)  mazingbrainiac5 years ago
The hinge at the back has a spring that pulls the trigger to the read-to-fire position.
aseaheru5 years ago
do you go softing with this?
MrTinkerer (author)  aseaheru5 years ago
I did once. I was very disappointed by the range. So I took it apart and built one with a 24" barrel.
multi tube ones = artillery
macingtosh6 years ago
i rather buy an rap4 one theyre a little bit cheaper but at least its profesoinal
MrTinkerer (author)  macingtosh6 years ago
I saw this one in:

It looks very effective. Looks like it runs of an air tank so no refilling per shot, very cool.
Colonel886 years ago
Is this reusable?
MrTinkerer (author)  Colonel886 years ago
macingtosh6 years ago
can you sell me one not that good with building this type of thing
pyro lucas6 years ago
do i absolutely have to buy a grenadey thingy? they are very evpensive!
MrTinkerer (author)  pyro lucas6 years ago
this instructable is what it is. If the system used something other than the airsoft grenade, then you would NOT need the coupler and the lever to push the valve. without those three things, this thing will be a completely different beast. At which point it goes off-topic of what this instructable is about.
killerkorn6 years ago
did you trim the ends on the ball. and heres a pic of mine, on the front of the barrel i added this cardboard tube and taped it up cause i was bored.
MrTinkerer (author)  killerkorn6 years ago
Yeah, trim 1/4 of an inch from the fins.
killerkorn6 years ago
yea sorry i got one more question, when your playing airsoft and using you bunker buster, does the paint you put on the handle come off on your hand?
MrTinkerer (author)  killerkorn6 years ago
nope. Used rustoleum. Paint stays on the gun.
killerkorn6 years ago
heres a better pic. of it
MrTinkerer (author)  killerkorn6 years ago
I love it. Looks great. The front grip is a great addition.
fenixxx136 years ago
I just built this launcher using a 24 pvc pipe 2 diameter
the first few shots were about 100-140ft perfect but, now its just reaching 50 ft not sure if its the green gas that I use but, im getting alot of silicon in the tube. I dont know if that is what is makign the nerf vortex or distance sliggish. Any suggestions?

Also did you have a problem with multiple firings. It seems that the grenade gets cold and has poor power coming out of the tube. Did you run into that problem?
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