Picture of Airsoft M72 LAW rocket launcher
Using an airsoft 40mm grenade shell for the reservoir and valve system, build a nerf launching LAW for about 60 dollars plus the cost of one airsoft 40 mm grenade shell.

WATCH THE VIDEO!!! - It explains how the launcher works.

Edit: People keep asking about the Strap/Sling. it is a 1 inch wide cotton webbing strap purchased at a local fabric store. Buy about 1-2 yards. Also buy velcro and 1 inch plastic buckles.

Edit 2: People STILL keep asking about the "Locking Mechanism". Seriously, it is nothing but a piece of plastic. But since I get questions on youtube, here, forums, private messages and email, I decided to make a video. WATCH the video in STEP 7.

EDIT #3: If others have a method to use a DIFFERENT GRENADE, Please Post a comment. Then we can Collaborate on making an instructable for using a DIFFERENT GRENADE. I have brainstormed methods of using other grenades but they all BREAK my Rule OF K.I.S.S. With that said, I ONLY RECOMMEND THE MAD BULL XMPB4 or the S-THUNDER GRENADE. Don't Ask me about other grenades.

Step 1: How it works

Picture of How it works
Illustration of what is happening inside.

My sorry excuse of a drawing of what is going on side the launcher.

Pictures are in sequence.

Color Code

Red = Grenade, 40mm type
Orange = Nerf Mini Vortex
Green = Green Gas
Blue = Valve
Black "T" = firing pin.

Picture 1 = Launcher ready
Picture 2 = Pin presses Valve
Picture 3 = Valve Open and Gas Explodes Out.
Picture 4-5 = etc....
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hey i know a way to make one that fires any 40mm grenade. not quite as simple as yours, but very realistic. i had bought an m72 body, de militarized for training. i put a 2 inch barrel in it. i drop the grenade in the back, slide in a actuator from an automotive power door lock, and close the back. i was able to get the body for $50, the actuator for $8, and the small 7.2v lipo battery that powers it for $15. oh, and the fire button for $2.
Is the Fiberglass just to make the outer tube, or does it also help reinforce the PVC, I want to make one of these, but if I don't require all of the fiberglass and additional parts and I can make a more basic version that would be great, but I was concerned with having pressure in the PVC tube.
thecrow1172 years ago
hey so far ive made one for my friend and am making one for myself i also have a 3D printer so i designed a trigger for it and also am going to design a part for that goes on the aluminum rod to depress the button is here is the link to the trigger http://www.thingiverse.com/thing:104019?save=success
Building one as we speak, this is like 3 years in the making. I'll post a video once I'm done. Basically building to the schematics of this instructables, with a few minor differences. I'm using very similar parts, with the exception of a few, namely the grenade, and the shielded coupler. I realize that what you have posted are the exact specifications for a product that will 100% work, though, being unable to acquire such items was difficult, as I am in Canada. I have a fair understanding of all the parts and realize that essentially you're just looking for a rear-load green gas grenade, and a shielded coupler which reduces from 2inches to 1.5 inches. If you are looking to make an airsoft grenade launcher:
1. For a reasonable price
2. That doesn't look like plumbing parts
3. That is easily made within a week
4. That will rival any $1000 launcher on the market
5. Can be used on virtually any airsoft field
6. Will not be turned down for use, as all potato guns are (even though they may be the most high-tech thing out there)
And probably the most important part of this instructable, as all instructables by MrTinkerer:
7. Sticks to the best principal - KISS: Keep It Simple Stupid.
I have spent countless hours on the internet looking for a product that even rivals this, that is home made, for under $120.. Needless to say, there isn't anything close. Stick with this instructable, and be smart about it. If you read the directions one by one, carefully, as well as the comments, you will find literally EVERY answer you may have a question to. Even if you're a novice, this makes sense. Basically you could take the coupler, the grenade, and a piece of ABS or PVC and depress the trigger on the grenade with your finger, and you would have the most basic form of this weapon. The fiberglass as well as the externals are not required to make this weapon work. It just makes it much more functional.
Thank you MrTinkerer, you are a god among men. No joke.
I am going to school to be a gunsmith and machinist technician so I can start building my own guns, and eventually open the most bomb airsoft facility ever. I'm talking downed heli's, airplanes, indoor CQB, and outdoor scenario play. I have ideas to host a apocalypse day/week/month every year around halloween, where players will set out, and zombie-costumed staff by the 100's will attack unsuspecting players through ambush and surprise. Think COD and Battlefield maps, only real life. That being said, if and when I get my business up and running, I would love to work along side for your expertise and innovative standards in everything you do. Very impressed to say the least.
MrTinkerer (author)  thisishaggard2 years ago
Wow! so much flattery in the comment above. you are too kind. thanks. but, humbly, i am just a guy who likes to make stuff, nothing more....
I am very much looking forward to seeing your launcher. Please send me a youtube link when you are done.
Hitman2273 years ago
I live in Canada and I cant see to find part no. 3001-215. Part no. 3000-215 is avalible but Im not going to purchase the grenade unless the grenade fits in that coupler. On the fernco website it says that part no. 3001-215 is 2" CI, PL. or ST. to 1-1/2" Copper or 1-1/4" PL while part no. 3000-215 is 2" CI, PL or ST to 1-1/2" CI, PL, or ST. I assume that the grenade will fit in part no. 3000-215 becuase the 1.5" end is 38.099999999999994mm's and should fit the 40mm grenade snugly. Thoughts?
MrTinkerer (author)  Hitman2273 years ago
Yes, whats important is that one end has an opening 1.5" or as close to 40mm as possible and the other end has an opening that is the corect size as the pipe you are using.
OK Thanks.
Hitman2273 years ago
How much did this cost in total?
MrTinkerer (author)  Hitman2273 years ago
Biggest cost in the grenade. Should cost 100-120 total.
OK. Thanks!
Rango193 years ago
Ive finished my law, and it turned out great. one problem i have is that the grenade (Mad Bull XM-PB4 Dummy Round BB Grenade Shell) will jam. after firing it once ore twice, the valve that is pleased does not come back out all the way. this makes it unable to be filled. i had my friend bring his mad-bull shell over and it did the same thing. did you have this problem? if so, how did you fix it?
on airsoft grenades you need to push the button in until you hear a click with a pen or something similar and release this resets the grenade.
MrTinkerer (author)  thecrow1173 years ago
Yeah. My mad bull does the same thing. I carry a nail for resetting the valve. Just press the valve all the way to the bottom. It will click when it is reset.
gnazaire3 years ago
Is there any substitute to fiber glass???
MrTinkerer (author)  gnazaire3 years ago
carbon fiber
If we wanted to go for carbon fiber, what would you recommend? Multiple layers like you did with the fiber glass? Single layer with a thicker sheet? I understand that using the fiber will probably make the build more expensive no matter what, but I'm just trying to minimize cost while making the outer tube (hopefully) more durable.
MrTinkerer (author)  theRx3 years ago
Fiberglass will be significantly less expensive even if you did 5-6 layers. Fiberglass is very strong even with 2 layers.
cdaniel23 years ago
Just out of curiosity, would the launcher be able to fire loaded 40mm grenades instead of nerf balls? Like, if I loaded the grenade and left the nerf ball out, would it damage the weapon?
MrTinkerer (author)  cdaniel23 years ago
not sure
This is still me. I've also noticed that it uses a different type of grenade. So, if I loaded a bb-type 40mm grenade, instead of the multipurpose grenade and Nerf rocket, would it damage the fiberglass tube?
boredom994 years ago
Hey where do you find nerf balls I already checked walmart they didn't have it and I don't know if toys r us has it. I know that Toys r us and everything discontinued their sale of nerf vortexes for some reason so where could you find those?
how many times do u wrap the wax paper and mylar around the pvc
MrTinkerer (author)  awesomesauce244 years ago
3-5 layers. It depends on how thick the material is. We want a tight fit but we also want the pvc tube to be able to slide. the fiberglass shrinks a little as it cures.
yish19194 years ago
where did you get the gas can or online? cuz i buy things online more then in the stores
MrTinkerer (author)  yish19194 years ago
local store. i dont like paying for shipping.
yish19194 years ago
Which air grenade is better, or is all of them are the same and have the valve on the back?
blslespaul4 years ago
what is yours or anyones average range with the S-Thunder grenade? Im building several LAWS for friends and some of my contacts throught the airsoft manufacturers have stated that the XMPB4 has been discontinued through Mad Bull... Im only getting about 20yds with the S-Thunder grenades as the power source, yet we played 2 weeks ago with my LAW and I got a 175yd launch with the XMPB4 :)
searl24 years ago
I used an ignition system of a BBQ sparker and static-guard. It seams to ga farther that the green gas and it dosent take time to warm up. Just out of curiosity, why did you use green gas?
MrTinkerer (author)  searl24 years ago
I dont want an ignition launcher. This is a non-fire, non-ignition instructable to make it universally field legal. As far as I know most legal paintball and airsoft fields will not allow potato canons in their games. That is why I am using green gas in a non-ignition way. Just playing safe.
Cool! If only nerf wasn't so restrictive of power, then kids will be shooting each other with stuff like this (although injury can occur more, hmm...).
The3rdPunch4 years ago
I'm confused does it shoot bbs or a NERF ball?
MrTinkerer (author)  The3rdPunch4 years ago
Did you read Step 1?
PJPEEJ4 years ago
is the grenade reusable? i don't wanna spend another $80 on only 1 grenade. And also, are there cheaper ones? I plan on making this instuctable. Its totally awesome :D
MrTinkerer (author)  PJPEEJ4 years ago
Yes and yes. Google "S-Thunder grenade". I think 50-60 bucks.
Hey could you use 40mm PVC or CPVC instead of an expensive airsoft gernade?
MrTinkerer (author)  The3rdPunch4 years ago
I don't know what a 40mm PVC, so I don't know. Besides, my design is field tested and works great the way it is.
sorry if im being annoying but how much would it cost in total and when u fire, does the grenade thing launch too?
ok so I want to make your launcher but i want to use the s- thunder multipurpose grenade ,but i want to be able to shoot bbs and nerf rockets..any suggestions on making the grenade able to be taken out during battle so i can reload
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