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Pumpbow

Pump-action +bow
homemade plusbow pumpaction spring writeup

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#1 Ryan201821

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Posted 14 July 2010 - 08:40 PM

final.png

My main reason for doing this project was to take advantage of hopper clips, and them being so awesome. Having a pump action blaster, as opposed to having a normal pull back style blaster, increases rate of fire tremendously. It's also very beneficial to your accuracy. Instead of taking your hand off the main handle, pulling back the plunger, and putting it back on the handle, you have one fluid motion without changing your stance, or aim.

So, here is the Pumpbow.

P1010087-1.jpg

Of course mad props to Captain Slug for the Plusbow, and Split for that marvelous skirt plunger head.

The basic power system, catch and trigger are all very similar to the +bow. I added a few things I thought would make the original design better, aside from making it pump-action.

First thing to do was improve the handle.

P1010089-1.jpg

I removed the trigger guard and replaced the two piece of polycarbonate on the grip with a solid piece of wood. The worst part of the +bow is the handle, specifically where you put your middle finger. This, for me, is much more comfortable. I used small rubberbands (for braces) for the trigger return. I also beefed up the catch spring to give the trigger a harder pull. I did this to prevent accidental fire, in absence of the trigger guard. Before my war this weekend, I'll also wrap the handle in some foam for extra comfort.

Next I needed something to link the foregrip to the plunger rod.

P1010092-1.jpg

I used a 1/2" x 1/2" square aluminum bar for the plunger. The priming bars are 1/4" x 1/2" aluminum bars. To link them, I just used a 1/4-20 steel threaded rod, 2 1/2" inches long. That random shit in the back of the plunger is actually some hot glue wedged in there because of a miscalculation while using the mill. Whoops. I can work on something more permanent later, but it works for now. Also, it's pretty much imposssible to use any other tool other than a mill for the channel in the plunger rod. It's unfortunate.

Here's a better view, while it's being primed.

P1010088-2.jpg

And what it looks when it looks like when fully primed.

P1010094.jpg

Next order of business is the priming handle, or foregrip.

P1010093.jpg

It's mainly composed of two 1 1/2" x 5/8" 90° angles. Those are screwed into the aluminum priming bars, and to a 1/8" piece of polycarbonate on the bottom. The foregrip assemblage is guided by two 1/8" UHMW polyethylene bars that run the length of the draw, keeping the foregrip from moving down. The 90° angles ride 1/16" underneath the bottom plates and prevents the grip from moving up. The polyethylene works well since it has relatively low friction. The aluminum on aluminum rubbing isn't ideal, but it's not going to mess up the blaster at all. Next one I make, I will probably improve upon that. The grip is actually surprisingly comfortable. I enjoy this a lot more than a large semi-circle. I've sanded down the edges, and will probably put some type of foam on this later. Another thing on my to-do list is get a rubberband or extension spring moving the foregrip forward after being priming.

Last thing I did was make the stock shorter.

P1010091.jpg

The whole blaster is roughly 4-5" shorter than a traditional plusbow. It actually fits in boxes! With the stock being about 3" shorter, I can get a lot more leverage on the foregrip, making it much easier to prime.

====================

Miscellaneous stuff:

I used a [k25] instead of the [k26] (+bow), to make it easier to prime. It gets 6.5" inches of draw. With Slug darts I'm getting plusbow ranges, with almost three times the rate of fire.

Here's the firing video.

Overall, I'm extremely happy with this blaster. I can, and probably will provide some general templates/parts list for the design if anyone wants to attempt to build one. I might do a writeup in the future as well.

Enjoy.


Edited by Aeromech, 23 November 2015 - 12:27 PM.

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#2 Ice Nine

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Posted 14 July 2010 - 08:50 PM

Two words, Ryan.

Effeminate.

sub-optimal.

Edited by Ice Nine, 14 July 2010 - 08:50 PM.

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#3 archangel24

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Posted 14 July 2010 - 08:52 PM

Is there much frictions between the plunger rod and the priming bolt?
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#4 Phibonnachee

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Posted 14 July 2010 - 08:55 PM

Looks nice. Would it be possible to attach a foregrip to the +bow pump grip or would that make it more difficult to prime? This looks like it would be quite easy to do on a SNAP as well, unless 1/2" cpvc is too likely to break after putting in a channel...
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#5 Fome

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Posted 14 July 2010 - 09:02 PM

That's cool as hell Ryan.

I'm glad someone finally made a successful pump action +bow, it's been due for one for a long time.

#6 Doom

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Posted 14 July 2010 - 09:03 PM

Fantastic work. The pump-action modification to the +bow design should have been done much earlier.

I'd suggest covering your wooden handle with some polyeurethane varnish. It seems like a small detail, but it's worthwhile.

Edited by Doom, 14 July 2010 - 09:03 PM.

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#7 Ryan201821

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Posted 14 July 2010 - 09:11 PM

Structurally, this is >five kinds of overkill. And there is not one single thing wrong with doing that for a prototype. As for that wad of hotglue in the plunger rod, call that fine tuning, not any kind of accident. Congratulations!

Now that we've been shown a way, I'd expect a number of variations to appear soon. Actually, I know that LT has been working independently toward roughly the same goal, so the community may soon see a wealth of pump-action homemade styles.

I definitely encourage people to try out some new designs or building off of this design. Pump action guns are awesome. We need more of them. I'm tired of pull-back guns.

I do realize this is super overkill, but I'm quite glad I have a pretty much invincible blaster.

Is there much frictions between the plunger rod and the priming bolt?

I think I understand your question, but no it's pretty smooth. The channel is maybe a 1/16" wider than the bolt. When you return the handle forward it's really easy.

Edited by Ryan201821, 14 July 2010 - 09:12 PM.

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#8 Lt Stefan

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Posted 14 July 2010 - 09:29 PM

Well props to you for this design. As Bob said I do think it is way stronger than necessary but there is nothing wrong with that, especially if you have the tools to make it that way. I also think that your guide method for the pump is very creative and makes pump action a lot easier.

Now I know what to work on to make this type of design more accessible to the majority of the community, and once again good job.
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#9 TED

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Posted 14 July 2010 - 09:33 PM

Would it be possible to remove the pump action and put just a handle on the plunger rod?
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#10 Hipponater

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Posted 14 July 2010 - 09:35 PM

Very nice. The Al is certainly sturdy, though it require some specialty tools (mill), it adds a level of 'badass'. There's certainly a nice feeling in knowing that a blaster will almost never break.

Definitely an interesting idea for the guide for the pump motion, not something I had thought of when making mine.

It's always nice to see new and changing homemades, thanks.
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#11 taerKitty

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Posted 14 July 2010 - 10:37 PM

At risk of a little whippage, can the aluminum bar be replaced with a cable?
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#12 nostyleguy

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Posted 14 July 2010 - 10:44 PM

That just looks unfair. And the cocking looks alot easier than I'd have expected (though that might just be the difference between the [k26] and [k25]. I didn't think they were that different). Awesome stuff.
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#13 Daniel Beaver

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Posted 14 July 2010 - 10:44 PM

I just want to say:

Single Piece Side Plates. Fuck yeah.

That is all.
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#14 FatNerfer

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Posted 14 July 2010 - 10:57 PM

That's tighter then a frog's ass.
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#15 Zorns Lemma

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Posted 14 July 2010 - 11:02 PM

Would it be possible to remove the pump action and put just a handle on the plunger rod?

That seems pretty hard to do. Maybe you could have it pump up an air chamber that then fires to prime the blaster.
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#16 ahtanie

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Posted 15 July 2010 - 04:20 AM

Super sexy sick.
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#17 Carbon

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Posted 15 July 2010 - 09:46 AM

Very nice. Pump action is where it's at for ROF. It also seems to put more stress on the blaster, so there's nothing wrong with overbuilding.

This looks like it would be quite easy to do on a SNAP as well, unless 1/2" cpvc is too likely to break after putting in a channel...

Cutting a channel in CPVC sucks. It's easier to make the charge lever slide around the plunger rod, and push against a cotter pin, rather than sliding in a channel cut through it.

That said, the issue with doing something like this in a SNAP is that the trigger and handle is about five inches further forward, due to the catch engaging at the plunger head. It throws off the balance. Bringing it back to this thread: the +bow design has the catch/trigger at the rear of the plunger rod, so it's better suited for something like this. Can't wait to see this beast on the field.
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#18 ficksterkid

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Posted 15 July 2010 - 07:30 PM

That said, the issue with doing something like this in a SNAP is that the trigger and handle is about five inches further forward, due to the catch engaging at the plunger head. It throws off the balance. Bringing it back to this thread: the +bow design has the catch/trigger at the rear of the plunger rod, so it's better suited for something like this. Can't wait to see this beast on the field.

I can testify it is true that it is very hard to do because of the trigger, as my last week and change can prove.
That said, very great job on the gun ryan. I have been working on a pump action gun the last few days and this will definatly help improve my disign.
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#19 SonReeceSonJensen

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Posted 15 July 2010 - 10:30 PM

Yesssssss, an $80 alternative to a singled quadshot!

J'skidding, this with a hopper will in fact change nerf. Don't believe? Single a quadshot, then pm me.
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#20 Abyss Mods

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Posted 22 July 2010 - 09:57 AM

Are you going to be bringing this to Foam In the Fort II? If so, I fear that I will be shot multiple times by it! <_<
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#21 mrlegonerf

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Posted 08 July 2013 - 12:24 AM

Ryan, do you have any of these for sale? I really like them! And by the way, which do u like more? The Pumpbow or the Rainbow pump?

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