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BOSS9

Member Since 17 May 2011
Offline Last Active Mar 29 2018 01:00 AM

Topics I've Started

Prototype of an Internal Pump-Action Platform

02 January 2012 - 11:08 PM

First, we need some background. This is a scaled-down prototype. It requires 3 nesting tube sizes, and I chose to build this on a small scale using materials I had on hand before building a final version. This thing is not built for performance. It shoots ~60-70s, but I've never actually tested and never will, it doesn't matter. This is just a demo of a possible internal pump-action system that I’m hoping others can build on. It’s not very efficient in terms of plunger volume considering its overall size, but it’s the system I want for the final version.

This is post-mod (by almost a month), so it’s not a full write-up, and I’m assuming no one will replicate it exactly anyway in it’s scaled-down version. I do, however, hope others will use this concept in some way or another.


The “finished” product:
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Closeup on the ridiculously comfortable handle (based off a recon- but better):
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Closeup of the priming handle. I dislike vertical handles, but this was easier than a nice wood one.
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Sweet RSCB spacer, ‘cuz it’s nice.
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This uses a rainbow catch, with the catch notch at the end of the plunger rod- similar to Slug’s 2-11.
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An exploded view of the internals. The 1” PETG at the top is the plunger tube, with the spring rest built in to the end. The plunger tube is fixed in the “shell,” or 1 ¼” PVC.The plunger rod is made of ½” OD ⅜” ID PEX with ⅜” OD ¼” ID PEX nested inside to form the 360 degree catch notch. The priming slide on the bottom is 1” PVC and floats over the plunger tube and slides along the ½” plunger rod, pushing back on the section of ½” CPVC to prime it.
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To disassemble there are 3 set screws holding the front of the plunger tube in place.
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The entire internals can then slide out, leaving just the catch in the shell.
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The internal assembly.
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The priming slide and plunger pulled back. When in the shell the catch would be engaged.
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Unscrewing these two screws releases the spring rest from the plunger tube, and the plunger tube can be removed.
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With the plunger head removed.
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The priming slide.
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Closeup of the plunger tube. Note the awful materials and implementation of all of these parts. That will go away in the full-size version.
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Plunger head. Clusterfuck of various washers. Seals wonderfully, but has to be re-tightened.
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Catch/end of the plunger rod. That’s an “I fucked up measuring” snap-on CPVC spacer. Note the screws and beveling.
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Another closeup of the priming elements extended.
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The catch when primed (picture taken of the gun assembled).
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Trigger. Has been known to seduce fingers.
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Just like the recon. But better.
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And a nice closing picture. Can’t get enough o’ dat handle! HGNMMM.
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Questions? Hope I explained everything well.

If anyone can help me out with tubing sizes for the final version, that'd be great. The plunger tube (inner of the 3 closely nesting tubes) has to be at least an 1/8" thick, hopefully more- should be able to sturdily take screws. The middle tube has to be pretty thick/durable. More so than the PT. The shell can be relatively thin. Ideally I'd use 2" PVC for the shell. I want the PT to be ~1 1/2" ID. Preferably the tolerances between these would be pretty tight, for a smooth prime.