NerfHaven: PVC/CPVC Breech - NerfHaven

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PVC/CPVC Breech

#1 User is offline   iamthatcat 

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Posted 28 February 2012 - 10:59 AM

Here are a few tweaks to the PVC/CPVC breech. I added a wire dartstop and shrunk the dimensions of the loading slot. The locking lug has no tab or handle. I use the barrel to open & close it. The opening is .45" wide and 1.6" long. It starts .53" from the end of the sleeve. I cut a bit off the front of my PVC couplers. You may need to start your slot further forward. The sanded area of the CPVC is 3.8" long. The PVC sleeve is also 3.8" long.

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I sanded the CPVC barrel to fit inside the PVC sleeve. I started with 60 grit sandpaper, wrapped around the CPVC. Use several different motions, alternating regularly. There is less chance of the sliding area turning out irregularly shaped that way. I alternated combos of hands, which end I held, up & down or twisting motion and grip. I sanded until it started to fit. I then went up through a few grits ending with 240. One trick is to cover each end of the sliding area of the CPVC with duct tape to avoid making those areas too small. That would leave a leaky breech. Just remove the tape from time to time and sand those areas separately. Once it was done I went over it with a manicure sanding sponge to give it a smooth surface. It should take about 1 1/2 - 2 hours to sand. I probably spent as much time sanding with the rougher grit as I did with the finer.

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Here I fit the dartstop. I used a finishing nail I found in my parts jumble. Measure, mark & cut it carefully to insure that it does not stick out past the PVC.

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Melt that down into the end of both the sleeve and barrel until it is sunk in. I used a 30 watt soldering iron. I held it in place for a minute while it cooled down.

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Undo everything and clean up the burnt plastic. Mark the area of the back of the barrel that needs to be removed. This will allow the barrel to spin a bit, letting the locking lug sink into it's slot. I removed the material with a file. Glue the nail in.

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I made the locking lug from some scrap PVC electrical conduit. I cut a small chunk of material to match the width of the opening.

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Now mark the barrel for the locking lug. Pull the barrel out and file a notch for the lug. Go very carefully here as the location of the notch will determine how tight your breech seals. A tight fit will ensure a strong lug. Cut the lug to size.

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Next I marked, started and filed a small slot for the locking lug to mate to. Test fit the lug to make sure that everything is tight. File and fit the lug, slot and rear mating surfaces carefully. Clean everything scrupulously. Make sure to position the lug so that the barrel will rotate properly in the slot. Glue in the lug with epoxy or solvent weld it in place. If need be the lug can be dremeled away for servicing, replacement or adjustment.

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Grease it up well.

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Pop it on your blaster and give it a whirl! I added a piece of the NF's stock barrel as a front sight.

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It opens 1". There's an additional .75" to jam the dart into before the dartstop. I pretty much matched the opening size to this blaster. A breech for a BBUMB would need to be made longer I guess. Here it is with a 1.4" dart loaded.

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This post has been edited by iamthatcat: 29 February 2012 - 11:07 AM

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#2 User is offline   thesaz123 

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Posted 28 February 2012 - 12:28 PM

That is a very clean and beautifully done breech. I will most likely be making one of these for *insert name of one of my blasters*. Thanks for posting this writeup!
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#3 User is offline   NerfNoob10 

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Posted 28 February 2012 - 01:14 PM

This looks really clean. One question tho, about how long did it take to sand the cpvc till it moved smoothly, yet still had a good seal? I can see myself trying this and spending an hour sanding only to sand too much and have a horrible seal.
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#4 User is offline   iamthatcat 

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Posted 28 February 2012 - 01:29 PM

It took me 3 hours the first time. I was going very slowly and checking waay too often. The second took me 45 minutes as I was less fearful of over sanding. As soon as the end fits in tightly you can start going for finer grits. This should ensure a good seal and smooth action.

Edit: I realized after writing this that this IS the first one I did. The second one was smaller. So, adjusted, I suppose this can take about 1 1/2 hours to sand.

This post has been edited by iamthatcat: 29 February 2012 - 03:57 AM

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#5 User is offline   thesaz123 

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Posted 28 February 2012 - 01:31 PM

Why not just use a 5/8inch spade bit? It works great on the inside of 1/2inch pvc
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#6 User is offline   iamthatcat 

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Posted 28 February 2012 - 01:38 PM

That's on my Harbor Freight list :) I haven't tried that method yet.
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#7 User is offline   thesaz123 

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Posted 28 February 2012 - 01:44 PM

It works great, a LOT less work than having to sand cpvc, which clogs up your lungs, which leads to lung cancer, which leads to death.
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#8 User is offline   Phree Agent 

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Posted 28 February 2012 - 07:16 PM

This is a great write up. Unfortunately, I think it made this look too easy :P. I have tried both methods (sanding and drilling) to make a cpvc/pvc breech and I haven't been very successful on either one. I will just share my findings instead of blabbering longer:

When using the sanding method it is hard to get a uniform thickness for the Cpvc. This led to a bad seal for me and troublesome sliding. I guess this could be fixed by using a mill, but that is neither here nor there.

When I attempted the drilling method, I found it hard to center the bit which in turn either created a corkscrew-esk groove in the PVC sheath or if the drilling did go successfully, the hole was crooked from end to end.

Like I said, these are just my findings. You can take them with a grain of salt if you so choose. Just know, that as simple as this write up makes it look, it is quite difficult to make this sort of breech well.
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#9 User is offline   iamthatcat 

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Posted 29 February 2012 - 02:07 AM

Phree Agent, thank you for pointing that out.

I used a method of sanding I dub "fractal sanding". My theory is that if you use several different motions, alternating regularly, there is less chance of the sliding area turning out irregularly shaped. I alternated combos of hands, which end I held, up & down or twisting motion and grip.

As to the difficulty, the level of skill required here is basic. I truly think that patience here will result in a good seal and functioning. This isn't something you try right away though. Some way of chucking a piece of CPVC in a drill would also substantialy decrease the effort required. I tried a few ways and failed. There's a way to do it though.

I am always trying to improve the things I do for ease of repeatability by others. One thing you reminded me of, is that I have to include all details such as this. I will edit in my response. Thanks again!

This was my second breech. It's small and I had to move the loading slot forward so it's a bit fiddly in design. It was for a contest though. I'll make the sleeve longer and trim the shell to move the loading slot back on the next one. The seal on that one isn't as good as the larger one. I attribute that to the reduced length of the sleeve and the "undercut" or chamfer I attempted on the face of the loading slot. I think it may be important to keep that square.

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This post has been edited by iamthatcat: 29 February 2012 - 05:32 AM

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#10 User is offline   iamthatcat 

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Posted 22 April 2012 - 01:42 PM

I added a quick foam seal to mine when it came time to clean & tune my nf. I pressed the breech into the foam to mark the outside edge of the seal and cut out the circle carefully. I didn't trim out the center at this point because I have had problems with doing that in similar situations.

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I used gel superglue to adhere it, being sure to get good coverage. I pressed down on it and wiped away the excess glue.

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Lastly I cut out the center out with a razor blade and cleaned it up with a file. I added some grease to the whole breech for good function, as well as improvement of the seal.

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It improved the seal enough for the plunger rod to slow down more than usual, and even crawl to a stop near the end of it's travel (which it didn't do before).
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#11 User is offline   HasreadCoC 

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Posted 22 April 2012 - 03:17 PM

Between the accessibility of this breach (compared to getting brass), and the fact that I've been wearing out my couplers ripping the single'd barrel out every time to load a dart (when just testing stuff, I use a hopper at wars), I may actually finally have to make a breach. Most of this seems like stuff I could do in 10 minutes or so, with the exception of that little "lug" part. That seems a slight bit tricky. Anyway, any chance I could just use some 1/2" PVC for that part, rather than that grey stuff?

 Daniel Beaver, on 07 October 2012 - 06:07 AM, said:

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AKA: ObiWonTwo on Nerfrevolution, and most of the rest of the internet for that matter.....
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#12 User is offline   RedFear 

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Posted 22 April 2012 - 04:42 PM

The breech looks great. wouldn't a brass one be easier to achieve seal with though because brass nests? i might be trying this breech out with brass in a few weeks.

This post has been edited by RedFear: 22 April 2012 - 04:42 PM

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#13 User is offline   jackrabbit 

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Posted 22 April 2012 - 05:15 PM

@ RedFear- Brass is harder to find and is far more expensive, I think the breech was supposed to be easy to make with material accessible and cheap.
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#14 User is offline   iamthatcat 

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Posted 22 April 2012 - 06:17 PM

@HasreadCoC: Yup, 1/2" PVC is the same sizewise. I did the locking lug in grey conduit to be able to confirm when it's locked better, and to make it easier to dremel away.
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#15 User is offline   RedFear 

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Posted 22 April 2012 - 08:23 PM

 jackrabbit, on 22 April 2012 - 05:15 PM, said:

@ RedFear- Brass is harder to find and is far more expensive, I think the breech was supposed to be easy to make with material accessible and cheap.

ok then. i guess i wasn't taking material cost into account.
how much improvement on range is there with this?
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