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

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....

Comments

[Hitman227]

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]

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.

[Hitman227]

OK Thanks.

[Hitman227]

How much did this cost in total?

[MrTinkerer]

Biggest cost in the grenade. Should cost 100-120 total.

[Hitman227]

OK. Thanks!

[Rango19]

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?

[thecrow117]

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]

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.

[gnazaire]

Is there any substitute to fiber glass???

[MrTinkerer]

carbon fiber

[theRx]

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]

Fiberglass will be significantly less expensive even if you did 5-6 layers. Fiberglass is very strong even with 2 layers.

[cdaniel2]

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]

not sure

[cdaniel2]

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?

[boredom99]

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?

[awesomesauce24]

how many times do u wrap the wax paper and mylar around the pvc

[MrTinkerer]

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.

[yish1919]

where did you get the gas can or online? cuz i buy things online more then in the stores

[MrTinkerer]

local store. i dont like paying for shipping.

[yish1919]

Which air grenade is better, or is all of them are the same and have the valve on the back?

[blslespaul]

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 :)

[searl2]

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]

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.

[Inverted_Spectrum]

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...).

[The3rdPunch]

I'm confused does it shoot bbs or a NERF ball?

[MrTinkerer]

Did you read Step 1?

[PJPEEJ]

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]

Yes and yes. Google "S-Thunder grenade". I think 50-60 bucks.

[The3rdPunch]

Hey could you use 40mm PVC or CPVC instead of an expensive airsoft gernade?

[MrTinkerer]

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.

[PJPEEJ]

sorry if im being annoying but how much would it cost in total and when u fire, does the grenade thing launch too?

[airsoftchase]

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

[MrTinkerer]

no

[airsoftchase]

what is the greenish tape stuff?and where can i find it?

[MrTinkerer]

Green self adhesive felt.

[airsoftchase]

will the s-thunder fit as well as the mad bull in the coupler?

[MrTinkerer]

most likely yes. Remember the s thunder and the mad bull is a replica of a 40mm grenade shell. With that said, they will mostl likely have the same diameter.

[pablotheillegaltaco]

What is the locking mechanism for is it to hold the metal bar in place?