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Pumpsnap

Why let the pumpbows have all the fun?

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#1 Stark

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Posted 05 August 2010 - 12:23 AM

I like the Snapbow, and I like pump action, so I built a PumpSnap. This design is essentially Fome's Supa Snap (http://nerfhaven.com...showtopic=19880) with a pump grip sleeved over it. Granted, a few slight design modifications need to be made to accommodate the grip.

Here's the full gun.

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The issue with making the SNAP pump action is the catch placement. Because the catch on a +bow is on the plunger rod, the catch plate, and thus the handle and trigger, are farther back. This leaves enough room for the pump grip to slide back and forth. The clothespin trigger on a snap catches on the plunger head, which puts the trigger too close to the gun. To solve this, I simply made the pump grip extend beyond the front of the plunger tube.

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The pump grip is 1.5 inch thinwall PVC that I snagged from Zach (Venom). The coupler is there because his pieces weren't long enough, so I stuck two together. I'm looking into other ways to make the pump grip, because I would like to use something that people have easier access to. Because the grip has to extend past the barrel coupler, we need to shave the edge of the coupler down to fit inside the pipe.

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I then wrapped the coupler in clear packing tape and gooped it in. I used packing tape instead of e-tape because e-tape is really narrow, which means there's a good chance that the coupler would be crooked, and packing tape has an extremely consistent thickness of 0.003 inches. Just to be on the safe side, I drilled a 1/8 hole through the coupler and chopped off a hunk of 1/8 inch steel rod and made a retaining pin. This also serves as a dart stop.

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Remember, the grip has to slide over this, so don't use a screw or a bolt, or anything that will protrude from the side of the plunger tube. Now you're going to want to make your plunger head.

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I used the preeminent plunger head, but I swapped out the narrow bolt and wing nut for a 1/4 inch bolt and nylon locknut. I used a 1/4 inch bolt because the ID of all the washers I used for the head were 1/4 inches, so everything is automatically perfectly centered. I also used a retaining pin to hold the plunger head together instead of a screw because I didn't want anything mucking with the catch pin. Let's take a look at all the internals laid out.

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There you can see the similarities in the plunger head and wire priming mechanism between the PumpSnap and the Supa Snap. I didn't have a u-bolt that was small enough to fit inside the spring so I had to put it at the end. This puts a LOT of stress on the bolt, so I just covered it in locktite epoxy putty. There is simply a bolt that goes through the back of the pump grip, through the wire priming mechanism, and is fastened with a nylon locknut. This pulls the wire back, and is able to slide forward while the blaster is primed. The stock is simply a pvc T shoved onto the 1.25 inch pvc body. Next, we have the endcap. Normally on the back of the blaster and secured with screws, ours must be in the middle of the blaster and cannot be held in with anything that protrudes out from the 1.25 pvc. Thus, we use another retaining pin.

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This does not go through the endcap, rather, it sits behind it and simply keeps it from shooting out the back of the gun. All that's left is to construct your clothespin trigger and handle. Keep in mind, it needs to be fairly narrow, and you must have space for it in whatever you use for the pump grip/sleeve. I went with a fairly janky looking handle so that I could have it done in time for ILFF. I must say, it worked beautifully. I used this gun in every round that day, except for the cqb round.

Ranges are average snapbow ranges.

Edited by Stark, 05 August 2010 - 09:00 PM.

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#2 BustaNinja

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Posted 05 August 2010 - 12:29 AM

Stark, do you still have your original diagrams and stuff for the pump snap? We need to crank some out at Zach's sometime.

This thing shoots hella holla fiddle faddle good. It really is a poor man's pumpbow, and it works.
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#3 Stark

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Posted 05 August 2010 - 12:35 AM

The gun itself IS the diagram. I wrote all the measurements and stuff on the pvc, you just can't see it with the pump grip covering it. But yah, if Zach gets his hands on more thinwall, we'll mos def have to make a batch or two.
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#4 BustaNinja

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Posted 05 August 2010 - 01:01 AM

The gun itself IS the diagram. I wrote all the measurements and stuff on the pvc, you just can't see it with the pump grip covering it. But yah, if Zach gets his hands on more thinwall, we'll mos def have to make a batch or two.

Good good. These things ownage little children. I'm gonna look at your pictures more to pick apart the plunger head. What spring are you using for it?
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#5 Fome

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Posted 05 August 2010 - 01:07 AM

That's really awesome man, great job.

#6 taerKitty

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Posted 05 August 2010 - 02:21 PM

Looks great, but could you edit it so you're posting the actual images and not the thumbnails? It would make things much easier to see.

Thanks!

I love how you addressed the length issue by just cutting a slot for the hoppah.

Using a cable to create the 'slotted plunger rod' is also a great way to do it.

Lots of great ideas here - you definitely made it work cleaner and simpler than I could have imagined.

Edited by taerKitty, 05 August 2010 - 08:45 PM.

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#7 Stark

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Posted 05 August 2010 - 08:20 PM

@BustaNinja: It's a k26. Let me know if you have any questions about the plunger head, it's pretty much just the superlative plunger head with a larger bolt.

@Fome: Thanks, couldn't have done it without your write-up!

@taterKitty: Bam.
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#8 cheerios

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Posted 05 August 2010 - 08:24 PM

Are you willing to contract these?
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#9 venom213

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Posted 05 August 2010 - 10:09 PM

Nice job on this Stark. It's awesome having witnessed much of the building of this and then seeing it rape face at ILFF. I don't think I'll be able to find anymore of that magical 1 1/2" Thinwall PVC which I am not happy about in the slightest. Other Aces in the Twin Cities might have it though, but the one I work at doesn't.
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#10 Stark

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Posted 05 August 2010 - 10:14 PM

Worry not! I am in the process of making another pump sheath thing using standard 2 inch pvc with sections of 1.25 inch coupler inside it. Hopefully that will make this homemade design a bit more accessible.
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#11 Carbon

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Posted 05 August 2010 - 10:31 PM

God damn.

This blaster just may make me retire my venerable SNAP-1 for a new model. Great job.
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#12 Stark

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Posted 06 August 2010 - 12:39 PM

Good news, I figured out a way to make the pump grip without using the mythical thinwall PVC!

You'll want a length of 2 inch Schedule 40 PVC and a 1.25 inch coupler. Cut the coupler in half. Sand the outside so it doesn't have that little ridge where the mold comes together, and sand the inside of the coupler until it slides smoothly back and forth across the 1.25 inch pvc body of your snap. Now, cut your 2 inch pvc so that there is room for the hopper and handle. Now, wrap one of your half-couplers in packing tape until it fits fairly snugly in the uncut section of your 2 inch pvc. Super glue or goop that sucker in. The other half-coupler will be going in the back, where the bolt goes through the snap. Because pvc tightens when you cut a section out of it, you won't need to wrap this one. Drill a hole for the bolt to go through the 2 inch pvc as well as the coupler. Don't glue this one in! The bolt will hold it in place, and if it is glued in, you will have to take your handle off every time you want to take the pump grip off.

Here's a picture of all the parts laid out.

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A closer look at the two couplers. You can see the one on the left is wrapped in a few layers of packing tape. Again, I use packing tape because it gives a more consistent thickness meaning that the coupler will be more straight. Don't drill the hole in the second coupler right away, put it in the pump grip first so that you can be sure the holes will line up.

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This is where I glued in the first coupler.

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And here you can see the rear coupler being held in by the bolt.

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Finally, here is a shot of the PumpSnap with the new grip.

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Now that I have a reliable way of making these I would be more than willing to sell them. Shoot me a PM if you're interested.
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#13 needak

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Posted 06 August 2010 - 06:10 PM

how much did it cost to make?
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Why the fuck would you put a bullet in someones head when you can just pump the bastard full of stefans until he's got so many welts and goose-eggs he looks like blueberry with pimples?

#14 TantumBull

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Posted 07 August 2010 - 10:40 AM

I think you just convinced me to rip my foregrip and mp5 "handle" (from broken airsoft gun) off of my Snap, which is no small feat. Bra-fuckin-vo.
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#15 BustaNinja

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Posted 14 August 2010 - 09:27 PM

Me and Stark are building one together! It's like bonding time!
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#16 TantumBull

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Posted 14 August 2010 - 10:55 PM

Me and Stark are building one together! It's like bonding time!

Hey, I'm making one too! It's like virtual bonding time! Yaaaaay!

I'm at the point where I have to start making measurements for the trigger, which is proving to be a thorough bitch when the segment of 1-1/4" PVC is so damn long.
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#17 BustaNinja

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Posted 16 August 2010 - 11:18 PM

Word up bitches. Don't use a k25 unless you plan out the plunger tube better. My trigger sometimes catches on the spring. Its easily fixed by holding down the trigger while you prime it, but just a heads up.

Also, i got mine working, and it shoots hella farr.
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#18 Stark

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Posted 17 August 2010 - 11:34 AM

Another suggestion, I would use 1/8" steel wire for the wire priming mechanism. That way, the wire is thick and stiff enough that it won't get tangled and bent over time.
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#19 BustaNinja

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Posted 17 August 2010 - 02:22 PM

Actually, I figured out that if you don't sand down the couplers enough, it makes an awful crack when priming. Now it works great. Thanks sand paper!
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#20 TantumBull

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Posted 17 August 2010 - 03:41 PM

I'll be uploading pics when mine is done, but I've discovered something that makes measurements A LOT easier: make the blaster in two segments and attach the back via 1-1/4" PVC coupler. It also makes the plunger assembly a lot more accessible for maintenance. You also don't have to add another sanded spacer for the pump as the coupler will act as a stationary one.

Edited by TantumBull, 17 August 2010 - 03:42 PM.

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#21 BustaNinja

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Posted 18 August 2010 - 12:55 AM

I'll be uploading pics when mine is done, but I've discovered something that makes measurements A LOT easier: make the blaster in two segments and attach the back via 1-1/4" PVC coupler. It also makes the plunger assembly a lot more accessible for maintenance. You also don't have to add another sanded spacer for the pump as the coupler will act as a stationary one.

I noticed that, and that is actually a really good idea. It would allow some more flexibility when it comes to the stock and how its set up.

Also, NEVER EVER make your pump handle out of ABS. ABS plastic tubes are about as strong as Minnesota is warm during the winter. My pump shattered on me where the rod goes to prime it. It kinda super sucked. I made a pretty permanent fix to it involving some sheet aluminum, but the reduction in weight isn't really worth it. Just use PVC for the pump handle too.

Also, I have a layer of think foam over the handle, and it helps wonders. Not only does it look super nice, but feels great too.
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#22 TantumBull

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Posted 20 August 2010 - 01:33 PM

Here's my variation on the PumpSnap:
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Biggest changes are the coupler connecting the halves and then not needing to use a coupler at the back for spacing because of the said connecting coupler. More info here.

Edited by TantumBull, 20 August 2010 - 01:34 PM.

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