First Attempt At A Homebrew Gun, With pics Options

[Carbon]

I've been collecting Nerf for years, but only discovered mods and homebrew guns very recently when I bought a couple of AT2Ks...and found out how bad they were out of the box. They rock now. Anyway, I've been spending a lot of time reading Boltsniper's amazing work. I want to build a F.A.R. eventually (who doesn't?), but the thought of taking on the entire project all at once was a little intimidating...so I decided to build a smaller project based on what I was learning. This is my first result.



What I was testing out in this gun was how to make a internally sprung plunger that used a firing pin. This is the plunger assembly:



The design came about after discovering that 3/4" endcaps fit just about perfectly in 1 1/4" PVC, with some minor edge sanding. The plunger is two endcaps (no O-rings) with a three or four inch length of tube. The dowel is attached to the bottom cap of the plunger with a cotter pin. I wans't able to find one long suitable spring, so I used two, separating them with a washer, plus washers at either end. Then, the spring assembly was capped with a 1 1/4" endcap. The hole for the dowel is very close to avoid rattles, so I drilled several vent holes in the endcap. The works is currently lubricated with a touch of vegetable oil.

I didn't want to even try a complex firing pin assembly, so I did something a lot simpler:



The firing pin is based off of something I saw on the Wikipedia page for rubber band guns, only upside down; the clothespin is glued down, and a hole drilled through it, into the plunger tube. I put in a nail, trimmed to the proper length (this took trial and error), and covered it with a dome of hot glue. The gun can then be fired by pressing the clothespin.



This is a closeup of the trigger assembly - once again, keeping it simple:



I drilled a hole in a piece of workable metal (this is a PCI slot cover), and slipped the firing pin through it. Pulling on the trigger lifts the pin just enough to release the nail.



I then cut a strip out of 3/4" PVC , and slipped that over the trigger assembly.



The barrel is 3/4" PVC with a nested Crayola barrel to keep darts out of the plunger. Fires stefans and micros (sonics work rather well). The barrel is fitted into a 1 1/4" --> 1/2" PVC bushing. The part is nice - the inside is shape into a half sphere, so it channels the air nicely. I'm using the hollow space in the handle to store the ramrod (1/2" dowel, stored in some 1/2" CPVC I have glued in there).

RANGE: The gun currently gets about 40-50 feet.

FUTURE PLANS: Well, get some O-rings on the plunger, for one. I've been having trouble finding them in the kinds of sizes or thicknesses I've been looking for. I'm also going to replace the dowel with an aluminum tube (the dowel tends to bind up a little). Cosmetically, I'll be painting it black, and probably adding a cosmetic clip/dart storage tube on the side to play up its similarities to a Sten. I'm having fun, I'll keep playing with it.

This post has been edited by Carbon: Jun 15 2007, 04:55 PM

[Crappy Nerfer]

Woah, good job. I love the simplicity and looks.

Yeah, o-rings will definently make it more air-efficiant. Also, maybe, a stronger spring. Finally the barrel looks too long, maybe shorten it.

Otherwise good job.

By the way, that trigger is marvelous.

[boltsniper]

That's very impressive. That is quite an ingenious trigger you developed there. It's extremely simple but looks to be quite ergonomic. I don`t know that I could've come up with that use out of a clothes pin. Kudos!

What's your stroke on your plunger. Since your plunger is in 1/1/4" PVC and he stroke seems decently long I don`t tihink your barrel is too long at all. You could possibly go longer with that kind of plunger volume. You definitely should get some kind of seal on your plunger. An O-ring would be best but even electrical tape will help. Like you said it might be kind of hard to find an O-ring that large.

Again, very nice job. Can`t wait to see it painted up.

[Pineapple]

Very cool.

Bolt's FAR, while a technological masterpiece, is also equally challenging to build; trust me, it's been at least six months now and I'm still stuck on the firing system (I'm making a variation, single shot.)

Your clothespin trigger and pin release is simple, yet works. I may take on that one just so I don't get stuck on bellcranks and linkage. I will, however finish the FAR variant if it kills me (which is pretty close right now).

Good job. Neat to see more innovation in homemades.


-Piney-

[Carbon]

Thanks for your comments, compliments, and ideas, I appreciate it!

Not only O-rings, but springs have been a challenge to find, CN. For this gun, the source I had was pretty limited. I decided to go with the two springs rather than one stiffer one I found, because I didn't know if I would shear off the nail with something stronger. The original nail has held up well, so I'll step up the spring and see what happens. Also, I'm finding that a stronger spring results in a stiffer pull (sorta figures), as I'm finding in the variant I'm making now. If I use much stiffer of a spring, I'll have to use a trigger linkage to get teh lever advantage to pull the pin....

The stroke on the plunger is about seven inches, boltsniper. I used your "rule of thumb" equation to figure the barrel, but it needs some more testing. You're right, a 1 1/4" plunger should have a huge air displacement, but I think my design is inefficient enough that I'm not getting the full benefit. I'll try out electrical tape, or maybe sandwiching in a rubber washer in between parts of a cut endcap. Is there anything in particular that I should be lubing the plunger with, rather than veggie oil?

I'll be really interested to see your implementation of the clothespin if you end up using it, Piney...my PCI slot metal is okay, but it still has a bit too much flex to it. I'm still trying to find something which is thin, easily workable with basic tools, but keeps its shape better.

Back to the bench, gotta try these ideas out now... thanks!

This post has been edited by Carbon: Jan 31 2006, 09:26 AM

[cooldood31]

Sweet homemade, Carbon. If you manage to get the thing working more efficiantly, I might make one myself (it would be my first homemade). It reminds me a bit of a sten (british submachine gun from ww2). Good luck with the changes, and I hope you find a good name for it.

[boltsniper]

[Carbon]

[FromAbove]

Carbon,

Great job with the pistol, simple and effective and theres improvement possible to make it even better.

Not to hyjack the thread but since there has been talk of trigger mech's has anyone considered the use of a sprinkler solenoid for actuation. I picked one up earlier last week thinking it was a "push" solenoid, turns out they pull, which led me to think of a design for a pistol, similar to the GNS, but with an electronicly actuated trigger.

I think it would be a rather expensive alternative, I paid around 14 dollars Canadian for the solenoid, it does give the freedom where mechanics may not allow, it would be easy to route wires around say a magazine or what not.

Just a thought.

[cooldood31]

Carbon, simplicity is half the reason I thought of a sten. Speaking of mass production, once the SNAP mk.2 is out, if it's shooting better (80 feet would be a good goal to shoot for) could you put the instructions out online, that would be awesome. I could easily see these things becoming the backbone of my arsenal.

A neat idea to do (once the instructions are out) is to have people pm you when they finish one, and you could keep track of the number of SNAPs produced in your sig. It would be interesting to see how many people start making these.

Once you have the basic SNAP shooting at a slightly higher range, another idea would be to try making some with turreted barrels (like an airtech 2000), or a bolt action clip (I think it's Ompa or Pineapple that makes these), of course you'd make the clip feed horizontaly right?

[davidbowie]

Here's a tip if o-rings are difficult to find: your local hardware store should have 3/4" sliding repair couplings (AKA Slip-Fixes). The plungers from these have o-rings mounted on them, and they are a very nice fit in 1 1/4" PVC. This would also allow you to have a PVC plunger shaft attached with standard fittings and solvent.

I love the look of it. Clip feed would be awesome, but all you really need is a breech, or maybe a turret. Ramrods aren't exactly convenient.

[LordoftheRing434]

Nicely done.

For your lubricant, I'd say that silicone will work best. I've said it before and I'll say it again - it works wonders for me. I've used it to lube my NF, SS1, and BBB and each is amazing.

[Carbon]

After meeting with dismal failure last night, I've made some serious improvements tonight, with a lot less work...

I've been trying out most of the suggestions. I added a stiffer spring, and swapped the dowel for an aluminum rod. But the plunger head was still too leaky. The tolerances were too tight for anything; one turn of electrical tape ended up getting scuffed, and trying to dremel in an o-ring ended up with me nearly gluing my fingers together, and nearly jamming the plunger into the gun. Even the idea of gluing a rubber washer that was large enough at the face of the plunger would end up getting jammed. But then I got the idea....why not put it in front of the plunger?




I took a machine screw, and dropped on a fender washer for support, a large rubber washer, another fender washer, and then added a nut. I drilled a hole in my face plunger, dropped it through, and then screwed on the whole assembly. This gave me a washer assembly which could be more flexible than a typical O-ring, and actually press against the walls of the tube, without adding a lot of resistance. LOTR's suggestion of silicone lube really makes it fly. The worst part was that the washer I found had an O.D. that was too big, so I had to cut it down with a knife. I can *hear* an improvement - if I try and cock the gun with a dart in the chamber, it makes a vacuum noise.

Tonight, I actually took it outside for some range testing, and the gasket showed up as improvements of about 15 feet. Firing a micro sonic:

55 feet
62 feet
64 feet
58 feet
74 feet
55 feet
72.5 feet

These are all measured distances, firing chest high, level.

The only downside I have right now is that the new, stiffer spring is a harder pull, so my PCI cover bends before it lifts the clothespin. Still searching for the elusive stiff, yet bendable metal...

This post has been edited by Carbon: Jun 15 2007, 04:55 PM

[sniper25]

I have attempted this type of side arm and have come to failure. this post has helped alot and the gun looks great. I have added a false magazine for looks , it looks like a WWII grease gun.

[LastManAlive]

If you are getting a vaccum seal, then that is actually good.

1) It shows you have a GREAT seal on the plunger. My NF doesn't even get a vacuum sound seal.

2) Since you are getting a vacuum seal, you will not need ramrods to load your gun. You can simply stick a dart in the end (if using stefans) abd pull it back. the vacuum will pull the dart with it.

3) A longer barrel would much be needed for better range. especially with that plunger. You might want to make the barrel as long as your plunger tube so tha the vacuum can pull the dart back with equal length, and not suck the dart into the chamber.

Nice work.