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FANG automatic Nerf gun

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: daberno123 » Sun Nov 30, 2008 5:27 pm

Looks familiar. :D

I like it but I must ask how the mag works. I don't see any springs in it but instead I see a string.

Any chance of blessing us with a video of this thing in action?
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Unread postAuthor: POLAND_SPUD » Sun Nov 30, 2008 7:29 pm

I think that there is no spring yet so he has to push ammo by hand (or pull upwards with the string) keep in mind that he wrote it's only 80% completed


the gun seems quite long... at least it is now longer than it could be... I know I commented on this just a few hours earlier but I think it is worth pointing out...

first of all, the air cylinder is an overkill... I know it has to have long stroke becasue nerf darts are long... of course it would be easier if you used spherical ammo (becasue you could use shorter/cheaper cylinder and a hopper for magazine) but since you decided to build a nerf gun it shouldn't be discussed...
however the way in which you aranged the gun 'made' you use longer cylinder.... to the fact that ammo is pushed forward though the tee means that the cylinder has to push the dart about 3 - 4 cm further (I don't know its acctual dimensions so it is just a rough guesstimate) that 3 - 4 cm which are unneccessary mean that the cylinder has to have 3 - 4 cm longer stroke and overall this makes the gun 6 or 8 cm longer ( I hope you can understand what I mean :? )
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Unread postAuthor: VH_man » Sun Nov 30, 2008 7:57 pm

As for your Cylidner thing, Would you reccomend possibly using a double acting cylinder?

I have three of them, And i want to make some kind of nerf gun. My friend and I always have a giant nerf war, and We always fight over who has the better gun. I want to win overall, 100%.

Im running into the problem that our homemades have to be able to shoot both stefans and normal darts........

anyway, As i said before, Sweet gun. You better get some videos up.

EDIT: anyone remember where the 3-way mod to the shop blowgun went? I could use that.
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Unread postAuthor: frankrede » Sun Nov 30, 2008 8:00 pm

john bunsenburner wrote:And now look at us in comparason! We are international, well educated, intelegent, young engineers each making their own ideas, each helping the others, each happy to welcome noobs like me. We, our mods and admins can be proud to belong to a community so great as ours is. Let us all do our best to keep is alive and the way it is for future spud gunners. Let us be proud and let us all make many, many more guns of all kinds and let us all present them in a language the average high schooler never even heard.

I find it ironic that you misspelled intelligent.
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Unread postAuthor: POLAND_SPUD » Sun Nov 30, 2008 8:17 pm

I bought a double acting cylinder... I know it'd be more stright forward to use a single acting one but I couldn't find single acting anywhere...

if you have the same problem you can always pump the other side with air (and have it act as an air spring) or use a 5 way valve (which has one advantage - you can use lower pressure for the cylinder and higher for the gun.... this might be very usefull if you plan to use higher pressures like 20 - 25 bar... there is going to be a lot of stress put on an air cylinder)...

so far I done only some basic tests on an air cylinder at 80 psi but everything worked fine...


EDIT: anyone remember where the 3-way mod to the shop blowgun went? I could use that
care to elaborate ?? did you mean blowguns for pumping tires ? ones with a button for releasing air ?
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Unread postAuthor: btrettel » Sun Nov 30, 2008 10:19 pm

Lots of comments. Thanks for the interest. I don't think I've ever seen so much interest in something I've done on a forum before. I'll try to respond to every one but if I miss you and you wanted a response, let me know.

One thing I'd like to say before I say anything else is that this project was on hiatus since August. The NerfHaven thread about this project shows that. Due to college I will not be able have access to the gun until December 20th because I left it at my parents house, so any requests for videos, damage photos, etc., will sadly have to wait. I'd love to do them but I have other obligations at the moment.

Concerning different ammo, I'm not going to try anything different aside from different weight Nerf darts. The design is rather simple and of course would work on different sized ammo.

One thing to keep in mind is that I used telescoping brass tubes. These tubes are made with high precision to have an air tight yet smooth fit inside each other. They are available in most hobby stores. Their sizes are limited to less than 5/8 inch ID but some fit Nerf darts very well. Using these tubes avoided use of a lathe to get similar precision.

As for shells, I've always found them to be clumsy. They're more work to make and in this case wouldn't add any benefit. They are necessary in many different applications though (or something between a shell and a sabot).

I intend to add a stock eventually. This is just what I could complete given my limited time. Any specific ideas on a stock are welcome.

A video would be great. I don't have any video equipment though so it's not possible at the moment. I'll see what I can do in the next few weeks.

As for damage photos, I can get some. I've done tests with some heavier styrofoam I've found and it can get some pretty good penetration, which I found surprising because I'm shooting low density foam at high density foam. The gun could shoot clear through 1 1/4 inch of styrofoam. I'll have to get some different materials to test when I do more tests.

I see a lot of comments about the look. I wasn't going for any particular look and used what was available so it does have a distinct look. For those who worry about me changing the look, I don't plan on changing it substantially because it's only a test for the more serious prototype. The most I'll do is add a stock, a trigger, and clean up the plastic near the handle.

I suppose that you could make your gun a little bit more sturdy by making it from malleable iron threaded fittings... they really make life easier (sometimes)... this will also alllow you to use higher pressures

ohhh and there is a dead space between the tee and the air cylinder... it seems that it can be minimized... I am not an efficiency nazi like JSR Very Happy but dealing with it will help to make the gun shorter


Iron's heavy so I didn't consider it. Higher pressures aren't a concern in this specific gun either, though I wouldn't be surprised if it could hold 250 PSI without issue as is. I'm doing my tests at low pressures like 30 PSI.

While I'm unsure, I think the space you are referring to is where the bolt hides. I've tried to reduce the length as much as possible. Without changing the air cylinder (which could be shorter) I probably couldn't reduce the length very substantially without reducing the barrel length. I plan on making prototype 2 use a shorter air cylinder, but possibly I'll use a longer barrel so it might work out differently.

@SEAKING9006: I agree with much of your points about NerfHaven. That is precisely why I don't post there often. Sadly, with the recent influx of new members to NerfHaven, the situation is only getting worse. The alternatives are much worse however. While you can find gold at NerfHaven, other Nerf forums are pure trash. That is why I don't bother looking elsewhere, except for here, because people here actually know what they're doing.

The magazine uses a small constant force spring. The side shown does not make the spring very visible. I chose a constnat force spring because helical springs will not make high capacity magazines very well. Because the displacement would be rather large, the increase in force would be rather large. Foam doesn't work well when squished.

The string only exists to help with loading. The magazine is internal for simplicity, so loading is done by pulling down the follower and dropping more darts in. Very simple.

first of all, the air cylinder is an overkill... I know it has to have long stroke becasue nerf darts are long... of course it would be easier if you used spherical ammo (becasue you could use shorter/cheaper cylinder and a hopper for magazine) but since you decided to build a nerf gun it shouldn't be discussed...
however the way in which you aranged the gun 'made' you use longer cylinder.... to the fact that ammo is pushed forward though the tee means that the cylinder has to push the dart about 3 - 4 cm further (I don't know its acctual dimensions so it is just a rough guesstimate) that 3 - 4 cm which are unneccessary mean that the cylinder has to have 3 - 4 cm longer stroke and overall this makes the gun 6 or 8 cm longer ( I hope you can understand what I mean Confused )


I agree about the length of the air cylinder. Shorter ones are available but not from McMaster-Carr, and initially I had not considered parts from elsewhere. As this is only a prototype I didn't worry much about it.

While I'm not sure I believe the reason the air cylinder is so long is because the force build up of the return spring must be small so the push occurs all at once instead of gradually (if you understand what I mean). The spring is prestressed and has a low spring constant. I don't care if it advances all at once so I could use a shorter air cylinder that is not prestressed.

I'm not quite sure what you mean in the second paragraph I quoted so if you could explain more I'm sure it would help.

As for your Cylidner thing, Would you reccomend possibly using a double acting cylinder?


I considered double acting air cylinders but they'd waste air and make the system more complicated. I wouldn't recommend them but they would work. If I already had a double acting air cylinder I probably would try it.

If you can disassemble the air cylinder you might be able to convert a double acting one into a single acting one by adding a spring. The one I have is one solid piece so that's not possible but you might want to consider it.

Actually, after some thought, air is like a spring, so if you make a small pressure chamber on one end of the double acting cylinder and leave it pressurized at a certain pressure level, the rod won't move until the other side has more pressure. This will act the same as a single action air cylinder but be a little larger. I would suggest this because you already have some double acting cylinders.

Hmm... POLAND_SPUD just recommended the same thing. It's worth considering, in fact, I might try it myself in prototype 2.
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Unread postAuthor: PVC Arsenal 17 » Sun Nov 30, 2008 10:39 pm

Hey that works almost like the one I'm building! Great minds really do think alike! Nice job!
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Unread postAuthor: SEAKING9006 » Sun Nov 30, 2008 10:40 pm

Speaking of which, how's it coming?
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Unread postAuthor: PVC Arsenal 17 » Sun Nov 30, 2008 10:41 pm

I only work on things when I feel like it... which is about an hour or so every 2 weeks. I have a hard time focusing haha. Just need to build the mag and I'm set.
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Unread postAuthor: SEAKING9006 » Sun Nov 30, 2008 10:46 pm

Same here. I haven't worked on a project in weeks. Hell, I have a backpack tank in the garage, solvent welded, PAINTED, and everything! But it still needs just epoxy on the leaks and a frame and straps. That's been there since August.
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Unread postAuthor: btrettel » Sun Nov 30, 2008 11:13 pm

PVC Arsenal 17 wrote:Hey that works almost like the one I'm building! Great minds really do think alike! Nice job!


I saw your gun a few weeks ago and was thinking the same thing. To me it's less "great minds think alike" and more "this is the most reasonable way to do it". CaptainSlug at NerfHaven has done some similar things too.

My original plan was to make a custom clip of sorts that held many different darts and was advanced by a trigger pull (like a linear version of the "RevoSemi", another Nerf gun here). I wanted to do that because it would have avoided an air cylinder, but after some thought, I realized it was actually much more complicated. This was back in May if I remember correctly. I sat on the idea for a while and starting actually working on it in late July. And then I sat on what I had built for a while before working for a couple hours to hook all the parts together. Life's like that.

Edit: One quick thought. Earlier I had said that it doesn't matter if the air cylinder pushes gradually. Yes it does. If the air cylinder didn't move all at once, the bolt would retract too earlier. So perhaps longer air cylinders are necessary. I'll experiment with them or try a double action air cylinder with an air spring I suppose...
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Unread postAuthor: btrettel » Sun Nov 30, 2008 11:26 pm

I just realized my "it's less that great minds think alike" comment could come across wrong and I can't edit it now. I don't mean to put down anyone, just that an air cylinder pushing a bolt or breech is the most reasonable way to do semi-auto Nerf. So great minds do think alike. :wink:
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Unread postAuthor: POLAND_SPUD » Mon Dec 01, 2008 1:47 am

I meant that the distance ammo has to cover while it is being fed from the magazine and pushed to the firing position makes you use an air cylinder that has the same stroke lenght as that distance...

consequently, any 'deadspace' there is makes you use a cylinder that is longer for that exact lenght... so acctually the overall lenght is increased by (2 * lenght of an unneccessary deadspace)...

if ammo has to go 4 cm through the tee this means that the cylinder has to have 4 cm longer stroke and this makes the gun (2 * 4 cm) = 8cm longer
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Unread postAuthor: john bunsenburner » Mon Dec 01, 2008 2:47 am

Ok something totally different to gun lengths:

You where talking about different kinds of fam darts, why not make 2 or 3 mags all with different darts, and you just use the best one for each situation, that would look pretty cool and maybe be really useful. It sounds like a powerful gun, i guess even foam darts can hurt so watch out, it would be a pitty if either some one took the gun away or if you hurt some one. Do some testing and show damage pics. Otherwise iahve to say once more great gun, good job...

p.s. I truely wonder what would happen if you used that thing on ply woad at maybe 250psi with lead slugs, if you decide to change your mind about using other kinds of ammo, and do what i just mentioned please get a camara first, we all would love to see the gun in action killing some ply woad...
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Unread postAuthor: Ragnarok » Mon Dec 01, 2008 11:21 am

Looks great to me so far. Obviously, it still needs the finishing off and cleaning up, but that shouldn't press you unduly, having seen your previous water gun work.
Actually, I hadn't heard anything about your work in some time, but seeing this, it's still looking good.

Sorry, my posts in the showcase almost always end up being boring sounding praise, because I don't often have many questions to ask to spice up the posts.
Asking where you got a part is generally useless, because US parts are useless to a Brit, and I seldom have questions I need to ask about how the cannon works - in fact, I often find myself answering that question for someone else when it's asked.

I think I know too much about spudguns.

@SEAKING9006: Ah, you have learnt that people on the internet aren't always as intelligent as found on our forums.

Nerfhaven is on the bad end of things, because it picks up a large number of younger kids, and... seemingly, from one post I've just found on there, the willingness to use highly coarse language on a forum full of younger kids.
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Does that thing kinda look like a big cat to you?
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