Build a Pneumatic Air Rifle

I have always enjoyed making pneumatic potato guns. There's always fun to be found with a gun that shoots anything you can fit in the barrel. So I've decided to post one of my more recent builds of a small caliber potato gun. This is technically my first instructable since my mini-fridge was just a slideshow, so please bear with me. Plus, I feel I have to redeem myself from that mini-fridge since it ended up all over the internet.

Generic Disclaimer: I'm in no way responsible for anything anyone decides to build/create/destroy with anything from this instructable. Don't even try to build anything related to this if you don't know exactly what you are doing. If you are unsure about anything in a build process with compressed air involved, seek help of a qualified individual or just don't attempt it at all. Be responsible and use common sense :)


A little background info.... The idea to make this particular gun design was kind of a spur of the moment idea. I had some small pieces of PVC laying around and an extra sprinkler valve so I decided to go at it with what i had(save some money too). Most of the potato guns I make are usually larger diameter barrels (1" - 4") but this time I wanted to go small with it. The diameter of the barrel I decided to use was 1/2" and the air chamber was 2". I wasn't sure how well this would perform but it seemed worth a try. I will try to be as specific as possible in the build process. If you don't like part of the design or have any feedback, please let me know. I do like to hear peoples opinions, good or bad.

Here's a materials list of the items I used in my version. Depending on the size you wish to build, this list can change dramatically.

This is not a complete list, these are just some of the main parts.

Main Materials:
1/2" PVC Pipe
2" PVC Pipe
3" PVC Pipe
2 - 3" PVC Couplers
1 - 3" PVC Cleanout with Plug
1 - 2" PVC Cleanout with Plug
2 - 2" PVC Coupler
1 - 2" to 1"threaded bushing
1 - 1" by 1" threaded pipe
1 - 24 Volt Sprinler valve
1 - 1" threaded to 1/2" slip Coupler
4 - 10" Hose Clamps
2 - 4" Hose Clamps
1 - Cheap Airsoft Gun
1 - SPST Pushbutton Switch
3 - 9 Volt Batteries
4 - 9 Volt Battery Terminals
Miscellaneous Pieces of Wood

You'll also need some pvc cleaner, pvc glue, expanding foam, liquid nails, and miscellaneous building tools.

Also, sorry if some of the pictures are crappy. The best thing I had to take pictures with during the first part of the build was a crappy cell phone.

Step 1 Air Chamber

I started with building the chamber to hold the compressed air. I build my potato guns by "eyeballing" it. So I don't have any exact measurements for this. Plus this is a chance for people to all have something different in case anyone actually decides to build something like this.

For the chamber, I used:
1 - 2" PVC Cleanout
2 - 2" Couplers
1 - 2" Slip / 1"Threaded Bushing

There's only one way those parts can be put together so it's a pretty easy step. Make sure to be generous with the cleaner and glue. You want to definitely make sure that you are getting a good air-tight seal on all parts of this project. Always wait the recommended curing time for the glue you are using. I've had caps pop off on parts before and it has the potential to be very dangerous.
The purple on the PVC is the primer in case anyone is wondering.


The next part has to do with the end cap. There can be many different ways and connectors for the end cap but it's all the same basicprinciplee. I decided to use a quick-disconnect fitting on the back of mine. I chose this because this can help with refill times (just keep it connected) and I don't like using tire valves. This is most likely the place where a leak will form in the air chamber. It can be challenging to get a good air tight fit on this. I found a pretty easy way to fix this by heating up the couple part for the inside of the cap to a very hot temperature. It screws on rather loosely (it expanded) but it melts the PVC on the inside and gets a good seal. There are possibly better ways of doing this but this way works for me.

After letting my glue cure it was time to put the cap in place. I didn't use plainTeflonn tape on the threads. I used tape specifically designed to seal gas. This tape is a little thicker and in my opinion has been more durable and reliable than plainTeflonn tape. But I'm sureTeflonn tape will probably work just fine.

At this point, the chamber can be considered done. I would recommend testing it before using it though. You can just put a 1" plug on the other end of the chamber and dunk it in a bucket of water to check for leaks. Be very careful with this also. If the chamber blows up in a bucket of water, it can be a very big explosion. My chamber was good andair tightt. I tested it up to 100psi. So I'm good to move on.

Comments

[dasadler]

When using the arrows, did you wrap anything around the shaft to fill the barrel? In other words, something for the compressed air to push against as it seems like the arrow just sitting there would not be propelled very far or with much force.

[CaptPikel]

Yes. A single paper towel (the blue shop kind).

[de0509]

actually, i think cellophane tapes are good for wrapping around cylindrical ammo for a good seal. they are so thin that you can make the diameter very finely tuned to what you want. duct tapes are too thick, just an extra round and its too thick, one round less, it leaks pressure. Plus, cellophane and PVC doesnt have much friction just same as the paper towel right. Thus, there will be no need to retrieve the paper towel anymore, just find the ammo back and its ready to be shot again. less messy reload. There are ideas on the net to make rifled bullets because rifling the barrel is a tough work. more accuracy.

[shingkai]

 Nice, but just as a heads up, pvc isn't very safe to use for storing pressurized air. It's not designed to handle air, and even if its rated far above what you're using it for, it's still not a good idea. The rapid decompression can cause micro fractures to form, which can eventually lead to horrendous failure (pvc shard shrapnel). ABS is more flexible and ruptures rather than fractures when it fails, so I'd recommend going with that. Looks great otherwise though!

[wewantska]

ABS is a bad idea it not for pressure it would break rather easier.

[shingkai]

 Yea pressure rated ABS is a lot harder to get, but ABS is actually safer. Even though it breaks more easily, when it does, the result is a split forming and the air rushing out. Because it's slightly flexible, it doesn't shatter like PVC.

[lemminggenocide]

abs is not safer. decompression at pressures used in amateur pneumatics won't cause micro fractures. It's a choice between having something that will rupture at lower pressures (which is sill very dangerous in hand held cannons) or something that will only fail if improperly joined or filled with much higher pressures than those achievable with with hand pumps or cheap compressors.
better no explosion than a less damaging one.

[CaptPikel]

 This is very true. ABS is not readily available to me unfortunately. I have a place I can get PVC from about 3 minutes away from my home. I have never had a compressed PVC air chamber blow up on me luckily. Which is why I always recommend wrapping the air chamber in duct tape. I'm glad you pointed that out. My photos don't show it I believe, but I did wrap the air chamber in duct tape before installing it. I usually run a tight overlay about 3 times on air chambers if I use PVC (about 2 rolls of duct tape for a 4 inch by 4 foot chamber). The duct tape may not prevent an explosion but hopefully should keep the shrapnel down. This is theory as I don't want to really test that :)

[shingkai]

 I noticed that and it should help, but I've heard of tests where 3" pvc wrapped in duct tape, denim, and placed in a 1/4" plywood box at 60psi resulted in pvc shards embedded in the box. Granted it was hit with a remotely triggered sledge hammer rig to trigger the failure, but still, it's pretty frightening.

Just an idea though, if you threw some metal hose clamp bands around the pressure chamber every few inches or so over the duct tape, and then another layer of taper over that, that might help prevent failure and minimize damage if failure does occur.

[wewantska]

how much pressure does this valve hold with the electronic switch ? does it leak?

[yeolddingdong]

hey I was blown away by this and if this is really your first 'structable its totally awesome !!!!!!!!!!!!!!!!!!!!!!!!!

[collingant]

how would you make it to shoot airsoft bbs?

[reaper75]

 how much does it cost?

[CaptPikel]

I'm not sure of an exact amount since I had most of the parts already. It would greatly depends on what store you got the parts from. A rough guess would be less than $50. Again, it mainly depends on where you get the stuff from.

[MadBricoleur]

Nice first 'ible!! It's like a plain solenoid pneumatic but looks sophisticated... I like it! I never thought of using airsoft pistol grips. That would be something to try with the cheap guns at the cheap novelty stores, and use the actual mechanics for something like a nerf gun, idk. :)

A suggestion: did you use Krylon Fusion brand paint? I've heard (from boltsniper and others on nerfhaven) that it bonds well to PVC and doesn't chip. I've seen it at walmart.

[Fuingurth]

So is this semi auto, or will i have to refill the chamber everytime i want a shot?

[CaptPikel]

This is a single shot gun. It probably wouldn't be too hard to make a semi auto one considering the small caliber. There wouldn't have to be too much movement.

[cowscankill]

Good design! nice job!

[dietpoop]

this is a very good looking gun, and great for the fact that its pneumatic even better, id like 2 see more