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Snapbow Mk. V, Revised

New writeup that sucks less!
homemade writeup SNAP spring

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#1 rork

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Posted 01 October 2010 - 12:29 AM

I have revised a few things in regard to this gun, and took some good photos that should make the writeup easier to follow.

SNAPbow Mk. V.

Materials Needed:

Main Blaster Body:
12 1/2" 1 ¼” sched. 40 pvc
1”x½” bushing

Handle/Stock:

#8x1 ½” screws (2)
1 1/4" PVC coupler
1x2 Poplar board (or the handle material of your choice)
6” ¾” sched. 40 pvc
¾” hardwood dowel (I prefer poplar, to match the handle)
½” pvc tee OR elbow
½” pvc 45 OR elbow

Trigger:

Industrial-strength clothespin
Roofing nail
4” zip ties (2)
8” zip tie
1 ½ “ angle bracket

Plunger Assembly:

Superlative plunger head
1 1/2" cpvc endcap
2 11/4" OD steel fender washers
1 appropriately sized nylon spacer (look at the photo)
1 #6 11/4" bolt
1 11/4" rubber fender washer
1 11/2" rubber fender washer
1 #8 finishing washer
1 #6 wing nut

12" of ½” cpvc
½” cpvc T
¾” pvc endcap
[k26] spring

Adhesives, screws, and so on:

Epoxy Putty
CA glue/Solvent weld
Goop
Hot glue
#6 ½” pan head sheet metal screws.

Tools:

You have to have a hacksaw and a drill. A dremel, a pair of PVC shears, a sturdy pair of pliers with a wire cutter, and a hobby knife are all highly recommended.

Main Body:

Cut your pressure chamber to length: 12 1/2". Wrap your 1” bushing in etape until it fits reasonably snugly in the pressure chamber (PC hereafter). Slather it with goop and seat it. Anchor it with 3 screws. Measure 8 1/2" from the front of the PC (NOT the front of the bushing) and drill the hole for your trigger pin.
006-4.jpg

Trigger Assembly:

Cut your clothespin down, fill with epoxy putty, drill, and assemble--pretty basic stuff.
038.jpg
039.jpg
040.jpg
042.jpg
Make sure the pin is cut long enough; the superlative head fits the PC more loosely than does a traditionally made SNAP head, and a too-short pin is an invitation to catch slippage. Zip-tie the trigger on. No glue is necessary, although gooping it on is fine too.
008-3.jpg

DON'T POST YET FOR CHRISSAKES


Edited by Aeromech, 23 November 2015 - 03:19 AM.

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#2 rork

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Posted 01 October 2010 - 12:30 AM

Handle:

Start with a 1 1/4" coupler. Grind out the center ring, then cut 1/4 of the coupler away.
Posted Image
Cut your handle at a slight angle, making sure the top is flat (or concave to match the coupler section) and all sharp edges are nice and comfy. Tack on the handle. Make sure it's straight. Drill pilot holes (1/8" or a bit less), then add your screws.
Posted Image
Posted Image
Snap it on the PC, butt it up against the trigger, and wiggle it side-to-side. This creates a couple of marks where the screw heads need to go.
Posted Image
If you love the taste of PVC dust, feel free to dremel out a groove, but I just drill a couple of 7/16" holes, like so.
Posted Image
Now's a fine time to add your vent hole as well.
Posted Image
The handle should be butted against the back of the trigger, holding the trigger in place and preventing overtravel. Solvent weld the handle in place, making sure the entire internal surface of the coupler is coated with solvent weld.

Plunger Assembly:

Make your superlative plunger head. Mount on your plunger shaft, using 2 screws or a pin. Add your spring, drill out your ¾” endcap, and add your handle.
Posted Image
Lubricate with silicone grease, and nothing but silicone grease. Insert into the PC, make sure the endcap is flush with the end of the PC, and drill a hole all the way through the handle, PC, and endcap on each side. Screw it down. To disassemble, you need only to undo these screws. Add a barrel and shoot people.
Posted Image

Optional Stock: Cut a 6" piece of 3/4" PVC at an angle. Nest a 3/4" dowel inside it with e-tape. Add a buttplate (I just use a couple of fitings and a bit of 1/2" PVC). Dremel out a groove to fit the trigger's zip tie. Glue the whole assembly on. It should be offset toward you slightly to prevent cheek diddle (a righty's stock should be cocked 1/2" or so to the left).
Posted Image

Optional Rail: Cut a piece of 1/2" PVC to fit under the PC, in front of the trigger. Glue it on. Now, things can snap on and off your gun.
Posted Image
Maintenance: Re-lube infrequently. Pull the plunger and wipe it down occasionally, to remove any accumulated grime. I recommend priming by holding the foregrip in your non-dominant hand, and pulling back with your dominant hand. Use a long, tight barrel--I use 16” of cpvc, lubricated with silicone spray.

Inevitable Questions:

Q: Rork, why did you not use TantumBull's Pre-eminent plunger head?

A: I tried. It sealed less well, caught less reliably, and created more friction. It sure does look pretty, though.

Q: How good IS the seal on these things? Those washers sure are primitive.

A: Generally, if you make it properly, you can fire it with your hand pressed tightly over the output, and the plunger will stop.

Q: One more plunger head question: How well do those things last? Does the epoxy putty wear down?

A: Hell of a long time, and no, respectively. To put it in perspective, my current SNAPbow is the third gun to be wrapped around my FIRST superlative plunger head. Thousands and thousands of rounds later, it catches and seals perfectly.

Q: How solid is this thing? [insert quibble about part] looks wobbly/flimsy to me.

A: It's a rock. I've messed with +bows, including some pretty nice ones, and I can confidently say that durability-wise, this is far superior to those or any other nerf gun I've seen. The only parts that could possibly get knocked loose are in no way essential to the working of the gun, as well (no, I've never lost a stock or an accessory rail, including those held by hot glue alone). If you somehow suffer a trigger or plunger malfunction (those are the only moving parts), a spare can be installed in less than 2 minutes.

Q: Is it comfy?

A: Yes. Of course, you can make the handle any shape you want, or modify the simple design I use by sanding it down, and/or adding a shaped piece of wood to the back.

Q: Raaanges. Tell me about the raaaaanges.

A: An elegant sufficiency. With the right darts and barrels, it should easily pass the 100' mark with slugs.

Also, you can cover them with tape and shit.
Posted Image

Edited by rork, 01 October 2010 - 12:42 AM.

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#3 Y-Brik

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Posted 01 October 2010 - 06:49 AM

Great to see updated Snap writeups!
I have a 1.5" PVC Snap and have one notable updayte- Instead of potentially unreliable E-putty (Mine always crapped out on me), I took a 1.5" endcap and went t town on it with a dremel, creating a PVC catch ramp that fits right where an E-putty ramp would go. It's another option for builders, though a bit more labor intensive.
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As I said I have not not alot of testes yet but I will be once I finish the mod.

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#4 burning-ice

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Posted 01 October 2010 - 10:41 AM

On a side note, mine has a 1/2" pvc coupler spring rest. It seems to be better becasue it is so loose and holds the [k26] nicely, if I were to nest it in two halves of a 3/4" coupler (cut in middle, bump grinded down) it would use less e-tape.

Overall nice revision. A+
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#5 Daniel Beaver

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Posted 01 October 2010 - 11:01 AM

Very good, the pinnacle of simplicity and effectiveness. Everyone should build one.

My only suggestion would be to use packing tape instead of e-tape for the bushing, as this seems like a superior solution.
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#6 utahnerf

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Posted 01 October 2010 - 02:36 PM

I've gotta say, I love the look of snaps. I've been on a homemade high recently and I want to make one of these, but my only question is... Cost?
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#7 taerKitty

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Posted 01 October 2010 - 03:59 PM

People claim between $20 and $40. Keep in mind, some of the parts come in bulk: McMaster springs come in 5-packs, PVC comes in 10' lengths. You may end up spending over $50 to make one, but you'll have enough parts left over for the next, and the next, etc.

Also, from my attempts, the plunger head takes a chunk of change.
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#8 Wes7143

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Posted 01 October 2010 - 04:14 PM

Although 1.5" PVC stuff has been brought up before in this write up, I don't believe its purpose in snaps has been fully realized. Using a 1.25" coupler as the handle bracket is silly. I used a few inches of 1.5" sch.40 PVC pipe, for the same purpose and it works way better than the coupler. Super tight fit, and it snaps on, and grips hard.This snap has the sort of handle clip I'm talking about.
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#9 rork

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Posted 01 October 2010 - 04:17 PM

A coupler fits and works perfectly, and for 50 cents, I eliminate 2 annoying mitered cuts, plus a measurement. Well worth it.

Edited by rork, 01 October 2010 - 04:18 PM.

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#10 Wes7143

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Posted 01 October 2010 - 05:17 PM

A coupler fits and works perfectly, and for 50 cents, I eliminate 2 annoying mitered cuts, plus a measurement. Well worth it.


If I may defend my opinion, the 1.5" eliminates the need to grind out the center ring, which takes far longer than cutting off a section of pipe. Both require the 1/4 being removed. The piping, for me, is simply more easily workable to exactly how I want it to be. Both do the same exact thing.
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#11 TxNerfer

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Posted 01 October 2010 - 05:25 PM

Might as well offer my $.02 When I made my SNAP, it came out to just over $30 (not including [k26]'s which I already had). Anyways, although I haven't tried it, I would suggest doing what stark did with his plunger head and using washers with a 1/4" I.D. followed by a 1/4" bolt and lockwasher. Lockwashers are a bit of a bitch to get on but I've found that the wingnut comes undone. Also, having everything auto allign is nice. When I attempted to make a second plunger head (my first one snaped off the plunger rod) then some things were out of allignment and it didn't catch properly.

Also, I'm just curious: Why do you cut the 3/4" PVC for the stock at an angle?

Edited by TxNerfer, 01 October 2010 - 05:29 PM.

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#12 rork

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Posted 01 October 2010 - 05:35 PM

Wes: hacking out the center ring of the coupler takes all of 15 seconds using a dremel with a sanding drum, with NO precision required, leaving me with a perfectly clean, even handle clamp. This fits perfectly with the idea of a SNAP as a gun you assemble, rather than fabricate.

I actually like a bit of wiggle room in the design, so I don't have to worry about drilling perfectly centered holes and whatnot. Plus, smaller bolts are cheaper and lighter. But in both these instances, do what you want.

I cut the stock retaining tube at an angle because it looks good. No other reason.

Edited by rork, 01 October 2010 - 07:10 PM.

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#13 Fome

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Posted 01 October 2010 - 06:26 PM

What exactly has been updated here, aside from the addition of a few pictures and a some measurements?

You know, the superlative head definitely needs an update. A larger bolt, locknut, and finishing washer are ideal, combined with a consistent 3/16" ID for your rubber and metal washers as well as your nylon spacer you'll get a self centering design that doesn't require any sort of super glue to hold it together. It also won't wriggle free or slam into your front bushing like wingnuts will either, causing your washers to loosen and "travel" laterally, fucking up your seal.

Self-centering and rock solid superlative plunger head with exact part dimensions:
Posted Image

From bottom to top:
1/2" flat cpvc endcap
10-24 X 1-1/2 SS pan head slotted machine screw (1" would probably be long enough, however)
3/16 X 1-1/4 metal fender washer
1/2 x .194 x 1/4 nylon spacer
3/16 x 1-1/4 metal fender washer
3/16 x 1-1/2 x 1/16 rubber washer
3/16 x 1-1/4 x 1/16 rubber washer
#10 stainless steel finishing washer
10-24 SS nylon insert lock nut
Epoxy putty

Also, a 7" draw is way more than is necessary to get any kind of decent performance. You're just overexerting both yourself and your spring.

I've made a lot of SNAPs, the first couple of which were initially made on your mk. V design and therefore I have a lot of reverence and respect for it. However, there's a lot of subtle improvements to the SNAP that this "new" writeup regrettably does not include.

#14 rork

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Posted 01 October 2010 - 06:56 PM

Essentially everything you said is incorrect. Firstly, the picture limit necessitated a new writeup. I simply wanted to get the best quality writeup I could up here, since I finally had time to complete it. I wasn't really looking for feedback from the likes of you. Now for the technical bits.

If you have problems with the wingnut hitting the front bushing, it's because you used the wrong part entirely. The wingnut allows me to fix anything that might go wrong with the plunger head with my fingers. All you have to do to hold your plunger head in place is to tack it together with super glue/hot glue/goop/Elmer's paste, tighten it down, and glue the wingnut in place to keep it from loosening One drop of CA glue on your screw threads to create friction and you're golden.. The epoxy putty holds the back rigidly in place, and the front does not suffer from any of the theoretical traveling problems that you describe, since the rubber washer keeps it spaced away from the walls of the PC. Oh, they could happen--if you dry-fired it a few dozen times. In which case, you'll have to take 30 seconds out of your busy day and re-align it.

7 inches of plunger stroke is not excessive, nor is it the most that can be squeezed out of a [k26]. The spring starts out slightly compressed, and does not reach full compression. Once again, you're talking out your ass.

What you seem unable or unwilling to comprehend is that this design has imprecision built in; I deliberately avoid anything that requires very precise measuring or cutting. In order for my plunger head to work, any hole that's within an eighth of where you want it to be will do just fine. eliminate that wiggle room, and you have to drill your holes much more carefully. Do I center my holes? Sure. but it isn't completely necessary to have a precisely centered assembly.

Before you get too smug over your "improvements," I'd urge you to do as I have and build several of these; then, instead of gluing shit to them, or curbstomping them, take them to wars and torture test them. Loan them out to people that can break a gun by looking at it. Drop 'em in the dirt. see how long they last, and see what breaks first. Then fix it, make it better--and engineer in ways to fix it more easily, in the field.

Edited by rork, 01 October 2010 - 06:57 PM.

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#15 TantumBull

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Posted 01 October 2010 - 07:39 PM

What ended up going wrong with the coupler/metal washer hybrid plunger head (I mean specifically, I know you mentioned what the results were)? I've made 4 now that all seal well and haves as much friction as any washer seal will make.

Also, that Snap in the write-up looks sexy. You're Snaps have always been the cleanest (for unpainted Snaps) that I've ever seen on here. Mine are all covered up in sharpie measurements. I think on my next build I'll be taking some 100% Acetone to the body, for removing the lettering and the marks I make.

Edited by TantumBull, 01 October 2010 - 07:39 PM.

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#16 rork

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Posted 01 October 2010 - 07:48 PM

I was honestly surprised, but the plastic ramp, even when centered, did not prime nearly as smoothly as the epoxy version, and the seal was probably 30% less efficient. On my latest SNAPistola, I tried one, and gained a big power boost when I went to the superlative. I suspect that with extremely careful fabrication, it would work about as well, but it does bear mentioning that the endcap fits fairly closely within the PC, whereas with the superlative, only the rubber ever touches. This is one of those things that really comes down to personal preference and how much time and effort you want to put into fabrication.
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#17 Fome

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Posted 01 October 2010 - 08:47 PM

If you have problems with the wingnut hitting the front bushing, it's because you used the wrong part entirely.



Mine did and I used the parts recommended by your writeup, I'd blame variances in parts rather than improper construction. If I had this problem then it's likely that someone else did or will too. I don't really give a shit if I'm hurting your feelings, my concern is for the people who might actually attempt to build one of these with an outdated and inferior plunger head design and therefore be met with the constant irritations of that design.

Old school superlative plunger heads break apart over time even with some kind of threadlocking glue, causing a host of problems, self-centering ones with locknuts do not. It's a simple substitution of parts for a much greater boost in durability and fabrication.

7 inches of plunger stroke is not excessive, nor is it the most that can be squeezed out of a [k26]. The spring starts out slightly compressed, and does not reach full compression. Once again, you're talking out your ass.


I made a SNAP with a cutdown [k26] for my nephew because he couldn't easily prime a full SNAP, it had a 5.25" draw and could send single bb darts 90-100' with a 8-round hopper. 7" is overkill unless you're shooting much heavier darts or you want to kill small animals.
Also, you obviously used a 3/4" round endcap in your writeup which adds a small, but necessary (especially with the draw length you're using) amount of available spring compression. If somebody only had 3/4" flat endcaps in their local hardware stores, then they're bound to run into problems.

Anyways, I think I voiced my issues with this particular build enough so I'll leave your thread alone.
I have made and used a lot of these, however, so "talking out of my ass", I definitely am not.

Edited by Fome, 02 October 2010 - 01:20 PM.


#18 rork

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Posted 02 October 2010 - 03:50 PM

The problem has nothing to do with hurt feelings (mine) and everything to do with the fact that you're a nitpicking jackass. And since my current SNAPbow has my FIRST superlative plunger head in it, It's pretty obvious that it has lasted just fine, and you're full of shit.

Also, I use a tiny little lock washer between the wingnut and the finishing washer, and will edit that into the relevant writeups--even though the issue that seems to have become so all-fired imporant is not the choice of nut (a locknut would be fine--just make sure you have a wrench) but rather the choice of bolt. Just in case any of the bamboozled SNAP builders Fome is so nobly concerned about couldn't figure that one out on their own.
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#19 TantumBull

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Posted 02 October 2010 - 04:21 PM

I was honestly surprised, but the plastic ramp, even when centered, did not prime nearly as smoothly as the epoxy version, and the seal was probably 30% less efficient. On my latest SNAPistola, I tried one, and gained a big power boost when I went to the superlative. I suspect that with extremely careful fabrication, it would work about as well, but it does bear mentioning that the endcap fits fairly closely within the PC, whereas with the superlative, only the rubber ever touches. This is one of those things that really comes down to personal preference and how much time and effort you want to put into fabrication.

You definitely have a point there about the ease of priming. You can make it easier with lots of grinding (of nail and endcap) and testing, but like you said, it really depends on how much time you want to put into it. I've never used a putty ramp, but I imagine its a much smoother prime as it ramps more gradually than an endcap. And that's weird about the endcap tightness, must be manufacturing differences.
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#20 MindWarrior

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Posted 07 October 2010 - 07:27 PM

What brand of epoxy putty do you use?
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#21 rork

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Posted 07 October 2010 - 08:06 PM

Loc-Tite, generally.
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#22 Whisper101

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Posted 08 October 2010 - 04:43 PM

I don't beleive you mentioned the lengths of the plunger rod, the roofing nail, or the diameter of the hole that one has to drill in the PC as well as the clothespin. I'm aware that the hole diameter is subject to variation but what do you typically use? What are the lengths?
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#23 TxNerfer

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Posted 08 October 2010 - 05:01 PM

The plunger rod is pretty much any length you want. It should be 12-13" though. The hole for the nail really depends on the diameter of the nail you're using. I suggest reading Carbon's recent thread on clothespin triggers. The nail length is kinda hit and miss. Idealy though, you want it sticking into the PC about an 1/8 of an inch. Also, unless I'm wrong, the hole in the clothespin for the nail really doesn't matter at all. On the side with the angle iron, it should be a snug fit. On the opposing side, I would make it so it can freely slide, as the PC takes the stress from the spring, not the clothespin. Hope that helps.
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#24 rork

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Posted 08 October 2010 - 05:02 PM

I use a foot of cpvc for the plunger rod. I cut the pin to length each time, but I recommend a hair over 1/8" sticking up inside the PC. The hole for the pin is a touch over 1/8"; I use a 1/8" bit and wiggle it around a little.
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#25 Whisper101

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Posted 08 October 2010 - 05:46 PM

Great!!! Thank you both!
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