15 replies to this topic

[Retiate]

A while back, Galaxy613 said something about cutting a piece of PETG and putting it over another piece of PETG for a breech. I thought this was a good idea, and so I decided to try it out.

I made a quick barrel to first test how well a standard 12" PETG barrel did. I decided to use my Pump Shotgun as the gun to test the barrels, mainly because it's one of the only couplered guns I have.
So, for the tests, I pushed a dart into the back of my heavy wall 12" PETG barrel, then pushed it up a bit so it was at the position it would be if I had loaded it with a breech, to keep things constant.
I shot it 3 times, using the same dart, and pushing it up roughly the same distance.
The dart landed an average of about 100' (From where I shoot, there's a wall of bricks almost exactly 100' ahead of me, and it either hit the bricks, or dropped right at them).

I then used the same barrel to cut my breech. So I started by marking then cutting the hole for my breech.
Sorry these pictures have horrible white balance, it was dark outside, so I had to use the work light in my room.
The cut is roughly 1.75" long.


Then I needed to make my breech cover. I cut a ~2.25" section of medium wall PETG for this. I then cut this piece lengthwise using a pair of scissors.


Then I slid it over the heavy wall PETG barrel. I sealed off one end, then blew down the other to see how good of a seal this basic set up had. It was terrible, air leaked out all over the place. So to improve this, I wrapped the breech cover in e-tape.


And here it is, breech closed.


I tested this set up to see if the seal improved, using the same procedure as before. It worked. The seal was so much better. To keep this seal, the slit I cut, now a small gap, had to be on the opposite side of the cut breech. To make sure this side was always down, I drew a line over it with a sharpie so I could tell where it was.


And the whole barrel, breech installed.
I had to spray silicone lube over the parts that the breech cover contacted since it was really hard to move back and forth.


I went outside and range tested again, using the same dart. I shot it 3 times again, and to my surprise, the dart went the same distance as before. I don't know it was because of the breech, but two out of the three shots, the barrel blew off. I think it was because I put the barrel in the coupler looser so I could pull it off without risk of it breaking.

Now, there are some definite downsides to this compared to a brass breech:
-The whole thing is flimsy, the section of the barrel that was cut for the breech can twist from side to side and it feels very weak. I don't think this will matter too much though, as it should normally be encased in PVC.
-The breech cover is harder to move back and forth, even with the silicone lube.
-Occasionally the breech cover will catch on part of the breech hole when it's closing. This really only happened when I was trying to close it really fast, but fast is how it will always be closed in a war situation.
-The added e-tape will make it tougher to add a breech handle.

I think I can work out some of these flaws. This was only a quick prototype. I'll update this as I solve these problems, or if I come across anything else worth noting.
Hopefully I can get this whole thing to work well. Maybe in the future perfectly nesting materials won't be necessary for a breech.

Edited by Retiate, 21 April 2008 - 04:56 PM.

[Quilan Fett]

I don't get how putting the e-tape n the outside of the cover helped it to seal.

[slowguitarman]

I don't get how putting the e-tape n the outside of the cover helped it to seal.

The tape probably pulled the outside petg in tighter around the petg barrel. Tighter=better seal.

[Galaxy613]

Thanks for testing my idea. I knew it was going to work.. but I didn't expect it to be as flimsy as you reported.

[ultra920]

but I didn't expect it to be as flimsy as you reported.

I think it was because I put the barrel in the coupler looser so I could pull it off without risk of it breaking.

Reading is fun.

[Galaxy613]

but I didn't expect it to be as flimsy as you reported.

I think it was because I put the barrel in the coupler looser so I could pull it off without risk of it breaking.

Reading is fun.

The whole thing is flimsy, the section of the barrel that was cut for the breech can twist from side to side and it feels very weak.

Indeed it is.

[Retiate]

Thanks for testing my idea. I knew it was going to work.. but I didn't expect it to be as flimsy as you reported.

I edited your name into the top of my post. Thanks for the idea.


I think the biggest issue I'm having is the breech cover catching on the edge of the breech hole.

And yes, putting the tape on was to keep the PETG on tight to hold air in. I am going to try some new things to see if I can make the breech cover easier to slide.

[Galaxy613]

Another crazy breech idea is to take CPVC, cut a section out of it that'll fit a dart and then do the same cover system... but I doubt it'll work as well. CPVC has a much thicker wall then even thick-walled PETG, so it might cut down powers a tad even with a good PETG cover.

*Edit* I'm going to try my CPVC/PETG idea. I'll re-edit this post when I'm done...

*Edit Twice* CPVC isn't as stable as I thought it'll be... it bends, but not at will. And probably not as much as PETG. Right now I'm working on the cover.

*Edit Thrice* Well that was a waste of CPVC. Once again the cover, as stated before, is a pain in the back to close and open. I would not suggest doing this to anyone. (the CPVC+PETG combo) I am also experiencing the PETG breech cover catching on the edge of the breech hole.

I'm thinking there's gotta be a better, not so friction-based sealing method.

Edited by Galaxy613, 21 April 2008 - 08:06 PM.

[Retiate]

Another crazy breech idea is to take CPVC, cut a section out of it that'll fit a dart and then do the same cover system... but I doubt it'll work as well. CPVC has a much thicker wall then even thick-walled PETG, so it might cut down powers a tad even with a good PETG cover.

*Edit* I'm going to try my CPVC/PETG idea. I'll re-edit this post when I'm done...

*Edit* CPVC isn't as stable as I thought it'll be... it bends, but not at will. And probably not as much as PETG. Right now I'm working on the cover.

Yeah, CPVC should definitely be more stable than PETG. It's way too tight on my darts, so it won't work for me.


Good news, I have an update.
I changed my e-tape-covered, tight, and high-friction breech cover to this:

I'll explain exactly what that is. I took off all the e-tape, then cut a new piece and covered just the gap.
It now slides VERY easily, easier than a brass breech. It also doesn't catch on the little lip anymore.

I tested the seal, it seemed good. So I went outside and tested to see how it did. This time I just grabbed darts out of my dart bag, since I already threw the dart I was using before in there.
I shot three darts, two hit the brick wall 100' away with enough force/height to go on for at least another 5'. The third dart apparently had no weight and so it flew all over the place and still hit ~85'.
So, excluding the weightless dart, it averaged at least 105'. The extra range could be caused by a few things including:
1. I used two different darts, and it could be that the dart I was using earlier wasn't quite as good.
2. It was nice and sunny out today. Yesterday, when I did my other tests, it was sunny, but not quite as nice.
3. This new breech set up somehow increased ranges a bit (probably the least likely, unless someone can come up with some kind of explanation for this).

This time, every shot I fired caused the barrel to come off. I'm pretty sure it's because my PVC slides easily into the coupler, and the back is cut at an angle (I just cut it real quick). The angle isn't that bad, but it's enough to keep it from sliding all the way back into the coupler.

And now:

Now, there are some definite downsides to this compared to a brass breech:
-The whole thing is flimsy, the section of the barrel that was cut for the breech can twist from side to side and it feels very weak. I don't think this will matter too much though, as it should normally be encased in PVC.
-The breech cover is harder to move back and forth, even with the silicone lube.
-Occasionally the breech cover will catch on part of the breech hole when it's closing. This really only happened when I was trying to close it really fast, but fast is how it will always be closed in a war situation.
-The added e-tape will make it tougher to add a breech handle.

So far so good.
Now it's time for a PVC case.

[Galaxy613]

BTW I updated my post again.

So you got rid of the E-tape ladened-ness? I should try that also. One min.

*Edit* I too need to cut a new piece of medium-walled, but I did get a few shots off and it seemed to work decently well for me and my CPVC.

*EDIT!* Confirmed, my breach is now functional too. No apparent loss of power, but it's too dark to go outside now... I am going to take pictures of my breech and breech cover to compare.

*Edit 3* Ok, here's the pictures of my CPVC/PETG hybrid breech.

Overall shot of my breech, ammo, and leaky, coupler'd AT2k.



As you can see by the grooves in my CPVC, I do not have the luxury of a Dremel. (yet) So what I did was I used a hacksaw to cut the front most, and the back most of where I wanted my breech opening to be, then I did cuts between them then used a box cutter to cut them out. Then I used a box cutter and a file to smooth and debur the whole area. The darts are 2inches long for the record.



Here it is in the AT2k with the breech still open.



Here is it closed.

One thing that ISN'T shown is how much of a gap there is with the medium-walled PETG. Retiate, I assume theres only a few mm gap on yours? Mine has a 1/4 inch gap. The e-tape was giving me trouble so I went with the safe route and just used a big piece of duct tape. I have to worry about keeping the gap down, but that's easy because the duct tape doesn't fit all around the PETG and leaves a window for me to align on top.

Edited by Galaxy613, 21 April 2008 - 08:39 PM.

[doubleshot]

BTW I updated my post again.

So you got rid of the E-tape ladened-ness? I should try that also. One min.

*Edit* I too need to cut a new piece of medium-walled, but I did get a few shots off and it seemed to work decently well for me and my CPVC.

*EDIT!* Confirmed, my breach is now functional too. No apparent loss of power, but it's too dark to go outside now... I am going to take pictures of my breech and breech cover to compare.

*Edit 3* Ok, here's the pictures of my CPVC/PETG hybrid breech.

Overall shot of my breech, ammo, and leaky, coupler'd AT2k.



As you can see by the grooves in my CPVC, I do not have the luxury of a Dremel. (yet) So what I did was I used a hacksaw to cut the front most, and the back most of where I wanted my breech opening to be, then I did cuts between them then used a box cutter to cut them out. Then I used a box cutter and a file to smooth and debur the whole area. The darts are 2inches long for the record.



Here it is in the AT2k with the breech still open.



Here is it closed.

One thing that ISN'T shown is how much of a gap there is with the medium-walled PETG. Retiate, I assume theres only a few mm gap on yours? Mine has a 1/4 inch gap. The e-tape was giving me trouble so I went with the safe route and just used a big piece of duct tape. I have to worry about keeping the gap down, but that's easy because the duct tape doesn't fit all around the PETG and leaves a window for me to align on top.

Actually my friend and I found a PERFECT breech for CPVC. His dad is a vet, and has syringes readily available. Well being modders, we tested every one and found a specific one had a perfect seal. He still uses it, but I moved out to brass.

[Retiate]

Nice job on the CPVC breech.
Yeah, the gap on mine is real small, probably around 2 mm.
With that 1/4" gap, does the exposed duct tape ever stick to the barrel? Or did you already solve that?
I kept the e-tape bare on mine, I don't think it will stick to my barrel.

[Galaxy613]

It SOMETIMES sticks, but it isn't too hard to get it moving. I guess if you REALLY wanted to you could maybe put tissue or something over that section, but it's fine for me. It usually doesn't stick on it's own unless you accidentally press on it.

Also, I found out the Longshot's stock 'barrel' fits very nicely over CPVC, so I put that on the end of my CPVC and taped it to my breech cover so now it's even easier to open the breech.

Anyways, I'm quite happy with this whole design, both pure PETG and CPVC/PETG hybrid. My first semi-original idea that actually works. Tomarrow I can get actual ranges from mine.

[Nonsense Man]

Today I went out to get some supplies to make a breech some 1/2in thinwall petg and 5/8in thinwall so expect a breech by the end of this weekend.

[Galaxy613]

Sweet, where did you get 5/8th thinwalled PETG?

[Nonsense Man]

At my local Petland in the fish section their was a lot of different sized pieces of petg for aquariums. They were in 3ft lengths. The 1/2in will serve as a way to push the dart into the main 9/16in barrel and the 5/8 will be there to keep the 9/16 in line and make it so the dart can't get stuck between the 1/2in pvc and the 9/16 petg.