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The Snap-5

14 months overdue and $3.57 over budget

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#1 Carbon

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Posted 19 January 2008 - 07:51 PM

Funny how life works. Here's some background on the design process for this iteration of the SNAP...

After I finished up the SNAP-4, I went to work on the SNAP-5. I had initially decided to scrap pretty much everything and start with a totally new concept. But as I worked, I noticed things getting more and more complex...which goes against pretty much everything that I want the SNAP series to be. So, I lost interest in building...and then a whole lot of life happened.

SPANO this last summer was educational in a lot of ways. Being my first war, I was able to see what really worked. And the basic SNAP performed well all day. Simple is better.

Getting back into building, I decided that the only way I would approach a new SNAP would be to address issues with the design of the SNAP-1. Why mess with what already works?

One of the things that bugs me about the basic SNAP is the stick that comes out of the back when it's ready to fire. However, the SNAP uses a narrow spring and wide tubing. Even if I were to use a wider spring, that would present a problem with the spring bending slightly and snagging on the catchpin. And, no stick coming out of the back also creates the problem of how to cock the system. Approaching all of these issues led to the SNAP-5. (As per usual, I'm posting it when it still has issues to work, but the entire concept is sound.)

As per usual, this gun wouldn't have been possible without all the fantastic work that comes out of the Haven, with a particular debt to Boltsniper, Ompa and Carrtoon.

The SNAP-5
IMG_6324.JPG
Looks a lot like the other ones, right? The differences are mainly under the hood.

This design addresses the problem of the chargerod sticking out the back, and how to charge the gun if that isn't used. The spring uses a collapsing guiderod, as well as a chargerod which can float on the plunger. The barrel slides back into the gun to press the plunger back, and then slides forward to firing position.

So, let's break it down, shall we?
IMG_6310.JPG

The charging system:
IMG_6309.JPG
IMG_6312.JPG

It's my usual reducing bushing combo, but the 1/2" part has been bored out slightly to allow the 1/2" PVC to slide snugly. I was initially concerned about this area being a major air loss, but that doesn't seem to be the case. Even so, I have an O-ring installed to minimize any potential leaks. The pushing end of the barrel uses a 3/4" -> 1/2" reducing bushing, rather than just a portion of 3/4" coupler; if it didn't, the rubber washer would bind against the end of the rod.
IMG_6320.JPG

The bushing is needed to make sure that the barrel doesn't wobble.

The plunger:
IMG_6313.JPG
IMG_6314.JPG

The rear is 17/32" brass, and the front guiderod is 1/2" aluminum (parts I had around that nested well). The aluminum is held loosely in the plunger head with a cotter pin, so the guiderod can slide into the plunger when it's pulled back. (This is the same concept that I used in the SNAP-3. It's actually the same plunger, just a little shorter. Modular parts are great, it saves me a lot of building time.)

The rear of the gun is also a reducing bushing:
IMG_6316.JPG

The brass was another part I already had on hand: a 17/32" brass barrel mounted in a stub of 1/2" PVC... Recycling! I just cut the PVC and brass a little shorter, and capped it off with a 1/2" endcap.

The other issue was how to load the gun, since the barrel would be moving back and forth. For the time being, I think my turret fits the concept well. With one hand, you can charge the gun with a pump action, and rotate a new barrel into place, four total shots.

Everything else is stock standard (clothespin trigger, plunger chamber style). I'm working on a new trigger cocepet, but that's coming later.

Things to address:
1. I still need to properly finalize my turret, and put long enough barrels on it. Also, I'm rather amazed that the PVC stub on the turret hasn't broken off yet. I need to epoxy that joint, as it's a major weak point.

2. The barrel isn't indexed at all so it rotates freely. It needs some kind of cowling over the entire thing so the rotating turret doesn't cause problems with a rotating barrel.

3. It doesn't give any indication on whether it's cocked or not. One good purpose for the chargerod!

3. Dead space. Just by nature of how it cocks, it has a lot of it. And of course, as I sit here typing and looking at the thing, I'm realizing that it's another good candidate for the in-line clip...definitely less bulky and complicated. I'll be testing it with that concept in place, and report on how it works.

It has the same general engine as all the SNAPs, so I i'm expecting similar ranges (no, I haven't tested it yet). Performance is patchy right now, partially because of the inconsistent barrels on the turrest. But the overall concept is sound.

More reports as they happen.


Edited by Carbon, 17 May 2016 - 10:56 PM.

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#2 Vimes

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Posted 19 January 2008 - 08:19 PM

Very nice Carbon!

I like the charge rod idea. I usually cut slots in the side of the plunger
housing and run a peg through the gun to slide the plunger back and forth.
This is a much easier design and, like you said, its perfect for the inline clip!

Excellent improvements!!
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#3 Quilan Fett

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Posted 19 January 2008 - 08:28 PM

Whoah! You just made almost the same gun as me only mine's clipped and almost done. I'll have it up by the end of the weekend. I used 2 CS-9173(?) springs glued together and put a peice of 1" PVC in the Plunger chamber-behind where the plunger head is when cocked- to support the springs. I think you should consider this, because yours looks like the plunger would have alot of extra friction. Other than that, nice job.

Edited by Qui'lan Fett, 19 January 2008 - 09:01 PM.

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#4 Carbon

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Posted 19 January 2008 - 09:03 PM

Vimes: Thanks. I used what you described on two earlier guns...It's a lot of fun to play with. When I do that, I just end up with guns that are almost unusably long (like the SNAP 2 and 3).

Qui'lan Fett: Heh, funny how that works....looking forward to seeing yours. You're using the 1" to keep the spring from buckling? That really won't work on mine, as the spring is still too narrow (I've tried using it as the powerplant in a 1" tubing gun...it didn't work). I'm probably going to sand down the aluminum to get it moving a bit looser, but it's not as much friction as you might expect. The nested portion only has to slide metal on metal for about 2": the rest is sliding out of the plunger, which is very loose.
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#5 Vimes

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Posted 19 January 2008 - 09:42 PM

I used 2 CS-9173(?) springs glued together and put a peice of 1" PVC in the Plunger chamber-behind where the plunger head is when cocked- to support the springs.



Thats a good way to keep the force of the plunger linear.
Hmm...I have an idea, but I can't explain it very well. I'll make a prototype tomorrow if I've got the material and post a pic.

Perhaps if you used 1/2" PVC instead of 1", Carbon, it would fit over the spring better.
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#6 penguin807

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Posted 19 January 2008 - 10:51 PM

You're going to run out of space on your sig soon. I'm really liking how this year is turning out so far. Are you planing to make a Snap-6 or are you going to branch out and do other series as well? Either or excelent job as always. I gotta say, you're the one who's gotten me closest to geting off my lazy butt and building a homemade.

Edited by penguin807, 19 January 2008 - 10:52 PM.

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#7 Carbon

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Posted 20 January 2008 - 03:05 PM

I tried it with an inline clip today....much better.

IMG_6325.JPG
IMG_6326.JPG

Still four shots, but with increased simplicity and less weight. This is still the same in-line barrel that I've been using for all my projects, so some tweaking is still in order. Range seems comparable to other inline SNAPS (60-70 feet or so), but cocking is much easier than with the turret.


You're going to run out of space on your sig soon. I'm really liking how this year is turning out so far. Are you planing to make a Snap-6 or are you going to branch out and do other series as well? Either or excelent job as always. I gotta say, you're the one who's gotten me closest to geting off my lazy butt and building a homemade.

I gotta clean out my sig...I'm maxed out, as the hidden URL characters count towards the maximum. As far as future building, who knows? I'll definitely branch out if I can think of a better way to fling a dart with springs, but for now, I like working out the bugs in the basic design.

Edited by Carbon, 17 May 2016 - 11:00 PM.

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#8 frost vectron

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Posted 20 January 2008 - 05:32 PM

Great work, as always, Carbon! :)

I've been meaning to build a SNAP one of these days, but I just haven't got around to it yet.

EDIT: As far as the signature limit goes, I would just make a blogger or something with links/photos to each of your snap designs--then hotlink to that blog.

Edited by frost vectron, 21 January 2008 - 03:51 AM.

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#9 sn1per

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Posted 20 January 2008 - 08:07 PM

Now you have to edit and make your sig longer!
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sn1per I appreciate your humor, that made me laugh literally out loud.

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#10 el swifto

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Posted 20 January 2008 - 11:48 PM

I gotta clean out my sig...I'm maxed out, as the hidden URL characters count towards the maximum.

Maybe you could put a link to "SNAP seires"....
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#11 Carbon

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Posted 21 January 2008 - 10:35 PM

Things are coming along nicely.

IMG_6336.JPG
(If anyone's curious, the electrical tape is holding a loose zip-tie in place, so the nail won't leave the hole if I pull the trigger too hard. The trigger cover usually does that, but I haven't made one yet.)

I installed a pump-action handle tonight, so it's essentially become a four-shot nerf shotgun. It bears a lot of similarity to the SNAP-4, but I've improved on a few of the construction methods. The handle guide is 1" thinwall, just like before. On the 4, I had found that it fit perfectly into the hollowed out area on the front of my reducing bushing. I had tried using various blades to hack out the reinforcing fins I then drowned it in hot glue, hoping it would hold itself together out of fear. It eventually held, but the negative was that once it was together, there was no taking it apart.

I apparently only have to do something hard way once....
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IMG_6328.JPG

I just cut out notches, and now it fits beautifully. It's held in place with a single screw (it's lot a load bearing part), so I can still break down the entire thing if need be.

The slider is 1.25" PVC. I drove screws through it directly into the .5" coupler I have on the barrel (that the inline barrel attaches to).
IMG_6338.JPG

I lubed up the friction points with my plunger lube, and it's working pretty smoothly. More improvements to come.


Edited by Carbon, 17 May 2016 - 11:01 PM.

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#12 sam

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Posted 22 January 2008 - 06:15 PM

Couldn't you use the piece of PVC you use to cock the gun as part of the inline clip, since it is just dead space at the moment? It would make it pretty damn small.
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#13 Carbon

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Posted 22 January 2008 - 07:17 PM

Couldn't you use the piece of PVC you use to cock the gun as part of the inline clip, since it is just dead space at the moment? It would make it pretty damn small.

Yes, I could. Because I did *grin*.

There's pretty much no dead space in this design. Or rather, any dead space is currently being used as the in-line.

I installed a stock, and I hope to get a return spring up and running shortly. Pictures later.

Edited by Carbon, 22 January 2008 - 07:18 PM.

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#14 sam

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Posted 22 January 2008 - 07:57 PM

Oh your a stinker!
How comfortable is the pump grip? I think it would look sweet with a T-fitting as a grip, like on the SNAP 4
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#15 jwasko

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Posted 22 January 2008 - 08:02 PM

Questions abound:

1. How do you reload the in-line clip in your current setup? Is it still just couplered to something?
2. How is the pump connected to whatever pushes the plunger back (whether that is the in-line clip, or whatever).

...okay, so maybe "abound" wasn't the best word.
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#16 Carbon

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Posted 22 January 2008 - 11:08 PM


Oh your a stinker!
How comfortable is the pump grip? I think it would look sweet with a T-fitting as a grip, like on the SNAP 4

Funny you should mention that...pictures below.


1. How do you reload the in-line clip in your current setup? Is it still just couplered to something?

Yep, just yank off the barrel and drop in the darts.

2. How is the pump connected to whatever pushes the plunger back (whether that is the in-line clip, or whatever).

A picture is worth at least a paragraph of me trying to explain.

IMG_6344.JPG
The coupler joins the chargind handle/inline clip section with the barrel. The coupler is also where the charging handle screws grip in, through the slot in the 1" thinwall I'm using as a cowling.

Modifications for the night:

I added a return spring between the coupler and the body of the gun:
IMG_6348.JPG

Two benefits here: one, no longer having to manually move the charging pump forward. The other positive is that I can put an O-ring under the spring on the outside of the gun, to assist in keeping a seal.

Added a stock. This is, of course, removable. It's a plus over the design of the 2 and 3, where the stocks were integrated into the design.

I also improved my charging handle, using a 1.25" Tee.
IMG_6353.JPG

I don't think I'm going to add a section to the tee...my return spring is a bit too strong, and moving away from the linear action binds things up a bit much.

The relative size isn't that monstrous..it's only a bit bigger than the SNAP-1:
IMG_6352.JPG

And it's actually smaller than the SNAP-1.5:
IMG_6351.JPG

I'm probably going to end up cutting some coils off the return spring....it's a bit burly right now.

More tweaks to come...

EDIT: Finally got some ranges: six shots down my hallway, all landing at ~65', +/- 3 feet.

Edited by Carbon, 17 May 2016 - 11:04 PM.

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#17 DeceitfulSteve

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Posted 23 January 2008 - 02:46 AM

I'm probably going to end up cutting some coils off the return spring....it's a bit burly right now.

Wouldn't that make the spring harder to compress?

PS - I love watching the incremental improvements develop
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#18 Prometheus

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Posted 23 January 2008 - 07:07 PM

I'm probably going to end up cutting some coils off the return spring....it's a bit burly right now.

Wouldn't that make the spring harder to compress?

PS - I love watching the incremental improvements develop


It makes it easier, since there is less to compress.
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#19 DeceitfulSteve

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Posted 23 January 2008 - 10:13 PM

Actually, cutting coils increases the spring rate.
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#20 jwasko

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Posted 23 January 2008 - 10:33 PM

Stop feeding us your physics lies!

(Just kidding)
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#21 Carbon

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Posted 23 January 2008 - 10:48 PM

Actually, cutting coils increases the spring rate.

Heh, thanks for the tip....glad I didn't make any cuts.

I did some research, and It's counterintuitive, but true. I'd post the formula, but Google seems to be down (!!). Anyway, one of the factors in the formula for spring rate has you dividing by the number of coils. All other things remaining the same, reducing the number of coils would increase the force. Weird.
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#22 Diablo

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Posted 24 January 2008 - 03:56 AM

This thing screams "pump action shotgun," and I love it. If used in combination with a deodorant clip the rate of fire would be amazing.

I think it has great potential for an actual Nerf war. While it's lacking a tad on the range side of things, the rate of fire on this gun combined with a clip system would blow most other guns out of the water. Not having to move your priming hand from the comfort of the gun's foregrip lets you keep steady aim, reload, and fire all at once.

Excellent work Carbon.
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#23 Carbon

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Posted 24 January 2008 - 07:33 AM

Thanks, Diablo. As far as a clip, I've decided that I dislike them. Sure, I can hold six or eight shots, but it increases the chances of a jam (at least in my designs), and makes it much slower to reload. I'll take four shots over six less reliable ones.

That being said, I hope to improve the range. 65 feet isn't awful for a multi-shot weapon, but I'd be a lot happier with 80 feet.

More tweaks to come...
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#24 Carbon

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Posted 24 January 2008 - 09:41 PM

The night's improvements while questing for more range...

1 ) Properly vented the rear of the plunger, more than just the hole in the rear. I finally realized that there's no reason why I couldn't add my usual vent holes on the side, and be stylish about it...
IMG_6355.JPG

Yes, the trigger area is a lumpy mess right now. But I like the vent holes.

2 ) Changed the stock to something a little less bulky.
IMG_6354.JPG

3) Replaced the aluminum plunger stem with brass that I had sanded down a bit, and then lithium greased the whole mechanism. It slides much easier now.

4 ) An improvement to the plunger head seal. I noticed that the rubber washer was tending to bend backwards, losing part of the seal, so I added a large ID washer behind it...one of these:
IMG_6356.JPG

It seems to help keep the seal in a more upright position.
IMG_6360.JPG

5 ) Improved the seal at the base of my barrel (it was a little loose..added a few turns of teflon tape).

With these changes, it definitely feels like it's firing harder. So, I went out to do some range testing.....and got the same damn range as yesterday. However, it looks like I need a new barrel...my darts are now fishtailing like crazy. My current barrel is only 7" long, so I'm hoping that's the answer to squeezing out some more range.

News as it happens.


Edited by Carbon, 17 May 2016 - 11:06 PM.

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#25 Prometheus

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Posted 24 January 2008 - 11:10 PM

For a compression spring I refuse to believe that a shorter spring is harder to compress until I see a verified source. F = -kx, so if you cut it down, x is then decreased because you can't compress it as much, resulting in a smaller force.
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