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Longshot With Cpvc And '2k Pump Tube Breech

post construction writeup

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#1 atomatron

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Posted 26 August 2009 - 02:23 AM

I got a Longshot from Daniel Beaver for $10 and decided to try my hand at singling it. Here is the fruit of my efforts:

Overview

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My intention was to make a new CPVC breech with minimal deadspace and that I wouldn't have to worry about harming my fingers with. I had to move the handle forward two inches to accommodate the 3+1/2" to be able tocock it.

The breech assembly out of the shell:
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^visible are the bolts I added to reinforce the epoxy

Here's a drawing too:
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It's pretty straightforward, the purple thing is the breech cover, the little blue thing is a dart stop, black is CPVC, some measurements are shown.

Construction:(sorry, no pictures, this is post construction after all)

Took it apart,removed the stock breech and a lot of the internals

I made the breech using 14" of CPVC, I cut a loading slot 1+1/2" long, 2" from one end. The dart stop is roughly 1/2" from the end of the CPVC, I epoxied it directly into the orange/black pushing back part, NOT to the tube coming from it (the CPVC is in contact with the plunger head). Then I slipped the plunger tube over the cpvc (not forgetting that oring) and 2" of AT2K pump tube. 7" from the back of the breech I epoxied on half of a CPVC teeto attach the handle to. Then I cut up the shell to allow it to fit and to lock forwards


Operation:

Rest:
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Primed (back):
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Primed (forward):
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Loaded:
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Breech closed:
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I have some plans for improving it... Integration much?
Posted Image
[/evil laugh]

Questions/whatnot?
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#2 nerfitynerf

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Posted 26 August 2009 - 08:58 AM

Interesting. at first i was confused on how it worked because the breech opening went into the air tank(i forgot the technical name for it) i would try it but if i get my hands on a blue ls I'm going to keep it stock because the yellow ones are ugly as all hell.
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#3 Mr BadWrench

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Posted 26 August 2009 - 05:29 PM

Ive been playing with something similar only with brass and still using the magazine.... good work btw

Don
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#4 venom213

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Posted 26 August 2009 - 06:37 PM

That CPVC with the cap on the end in the last picture looks oddly familiar...................


Posted Image


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Did you base it off of my sadly underused design?

Edited by venom213, 26 August 2009 - 06:38 PM.

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#5 atomatron

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Posted 26 August 2009 - 08:07 PM

^kind of...

My design doesn't change the volume of the pressurized space (I think that's what the problem is with yours). It is based a little off of a valve in a brass instrument (former trumpet/Baritone TC here), my intention is to have a multiple stage release, The rubber washers I'm using (00) are very stiff. I think it will work well after I've lubed it and stuff.

There isn't much room to work with the LSFG integration I'm trying to work around that and make it function like a Splitfire.
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#6 Fresh

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Posted 27 August 2009 - 07:09 AM

Wow this is great. As long as the pump tube is airtight it solves my problems. My main complaint about the singled longshot is that the e-tape that sealed the part that primed the gun had to be changed often because it would get warped. It was a pain to open the gun but doing this would give a little power boost and im all o.c.d. about getting the most out of the blaster and the seal.


-Fresh
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#7 Nerf Bros

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Posted 27 August 2009 - 06:45 PM

Nice as always atom. I'm working on a way to copy the general design of this but lengthen the plunger stroke, most likely by trimming down the orange pusher piece and reinforcing it, so I can use 1.25 of Century Spring 836s (almost same as #49). Should be cool.
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#8 Jangadance

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Posted 28 August 2009 - 02:11 AM

Questions/whatnot?

I believe this is the gun I got hit in the forehead by as I was peeking from behind a tree @ about 50'.

Nice work all around, good luck w/ the integration!!
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#9 atomatron

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Posted 31 August 2009 - 06:33 PM

Thanks for the compliments.


This is the mock-Splitfire system I've been working on:
Posted Image
Posted Image

Compared to Splitfire internals:
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The valve taken out:
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And a simplified drawing: Before and after firing the two tanks.
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Purple goes to the pump
Blue goes to the tanks
Green is the rubber sealing things
Red is 10/32" threaded rod/spacer/nuts
Black is thinwall CPVC/CPVC endcap


...In theory it functions perfectly, unfortunately the tanks go "fffshhht" instead of the nice "POP" from splitfire tanks. It seals fine, just not shooting up to par with what I expected ( >10').

Is this normal for Hornet tanks?

Anyone see any problems that I don't?
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#10 atomatron

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Posted 31 August 2009 - 07:11 PM

I have noticed that if I pull the valve slowly it will leak, the rubber washers aren't thick enough to prevent what you have described. Usually I pull quickly so any leakage is minimal.

I think that new tanks might help, perhaps they are worn out or something is messed up inside them.

Edited by atomatron, 31 August 2009 - 07:12 PM.

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#11 atomatron

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Posted 14 November 2009 - 01:52 PM

An update.
Posted Image
A simple addition of 6 CPVC bits GREATLY increased the rof, I can get 7 shots off in 24 seconds (1 every 3.5 sec). compared to before when I was taking darts from my pocket.

And the mock-Spltifire turned into this.
Posted Image
I switched out the hornet tanks, added a check valve, an AT2K tank and replaced my trigger design with a blast button, the hornet tanks fire at the same time. That's a stub of aluminum on the 2k tank.
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#12 Drew is nerfing

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Posted 15 November 2009 - 09:06 PM

I did a 3k integration into the undergun and a cpvc breech much like you did and it works excellently. I hope yours turns out nice when it's all done.
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#13 Phibonnachee

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Posted 15 November 2009 - 11:42 PM

What did you use to make the breech cover? The "purple thing" in you drawing and how easiy does it slide?
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#14 atomatron

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Posted 28 February 2010 - 05:18 PM

A short video:

Link
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