9 replies to this topic

[Athune]

First off, this is an addition to CaptainSlug's Big Blast mod. I take credit only for the breach system.
When I first did this mod, I had the problem of the entire barrel shooting off the gun when I pulled the trigger (I wanted a breach-loader, not a muzzle-loader, so I didn't glue it to the gun). To fix this, I added male and female threaded adaptors to the barrel and wrapped them to the other bits with e-tape. However, having to screw and unscrew the barrel to load a dart really cut down on my rate of fire, especially since the threaded adaptors didn't always line up on the first try. I looked at lots of breach systems made by others here, but none that I found locked closed, and I feared that on this gun they would open upon firing, just as my first barrel had flown off.
This design allows the barrel to be unscrewed from the gun and pulled forward, opening the breach. After a dart is loaded, the barrel is pushed back down and secured with a few twists. The breach keeps the barrel in line with the gun, thus eliminating a few seconds of fumbling around. Now I'm sure something slightly faster could be done similar to a bolt-action rifle, but I like the simplicity of this design.

Here is the front of my Big Blast without the barrel or breach:

Since my Home Depot didn't have PVC 1-1/4" to 1/2" socket weld reducing hex bushing, I had to go with a 1-1/4" to 1" plus a 1" to a 1/2". To that I added a short piece of 1/2" SCH 40 PVC and a 1/2" female threaded adaptor which I sanded down about an eighth of an inch (less twisting). These were all glued together using hot glue (after I took the picture).

Here's the barrel:
It's just a 1/2" male threaded adaptor on a length of 1/2" SCH 40 PVC wrapped together with e-tape.

Finally, the breach:
The PVC in the middle is 2" SCH 40, with a 2" to 1-1/2" reducing bushing on each end, and a 1-1/2" to 1/2" socket weld reducing bushing at one end. The slots were cut using a 1-1/2" hole saw bit on a drill press to make two sets of holes which were then connected using a hand saw. I also used a spindle sander to smooth the edges somewhat. The 1-1/2" to 1/2" socket weld reducing bushing has the 1/2" end bored out so that the barrel can slide through it easily. I did this with a metal lathe, but I'm sure it could also be done with a large drill bit or a dremel.

The final product:

After the barrel is screwed onto the gun, the breach is slid over the barrel and then hot-glued to the body of the gun (not glued in picture). Because the pieces of the breach aren't glued together, they can be pulled off the bushing glued to the gun, thus allowing the attachment of other barrels (I made a quad-barrel attachment that can fit on here. If anyone's interested, I can post a write-up for that later).

So, what do you think? Any comments, questions, critiques, and suggestions would be more than welcome.

Edited by Athune, 30 June 2007 - 02:28 PM.

[Athune]

basically, yeah. What do you think?
Please, I'm begging for some feedback here.

Edited by Athune, 30 June 2007 - 02:58 PM.

[keef]

How does it work? I don't see it, and wouldn't you lose a shitload of air in that breach?

[frost vectron]

No.

When you want to reload, you pull the 1/2" PVC Barrel out. You insert a dart through the slot(s) cut in the larger PVC. When you want to fire, you push the 1/2" PVC back inside to form an air-tight seal.

I am a little curious why there are two slots in the breach cover--I think that just one is necessary. It seems to work out fairly well for you, so that's what matters most.

I think brass would offer the easiest solution, but it's fairly hard to find. This breach is a little complicated, but sounds very robust.

Great work. I hope I understood the concept correctly.

[keef]

No.

When you want to reload, you pull the 1/2" PVC Barrel out. You insert a dart through the slot(s) cut in the larger PVC. When you want to fire, you push the 1/2" PVC back inside to form an air-tight seal.

I am a little curious why there are two slots in the breach cover--I think that just one is necessary. It seems to work out fairly well for you, so that's what matters most.

I think brass would offer the easiest solution, but it's fairly hard to find. This breach is a little complicated, but sounds very robust.

Great work. I hope I understood the concept correctly.

Ok, thanks, now I get it...
But why is the breach opening pipe so big?

[Athune]

You got the right idea frost. Here are a couple pics of the breach in action; I probably should've taken these for the write-up:

Breach open:


Breach closed:


There are two reasons there are two slots: One, it makes it easier to see what I am doing when I load a dart (I usually load from the bottom slot), and two, I anticipated accidentally dropping darts in the breach while loading, and I didn't want to shake my gun upside-down to get them back out. With two slots, a dropped dart simply falls through.

Thanks for the feedback.

But why is the breach opening pipe so big?

So when I cut slots big enough to comfortably fit my fingers in for loading, there was enough pipe left to maintain the structural integrity.

[PointBlank]

Wow, I have got to say that is pretty cool.

[keef]

Ohhhhh, in that case, I'll have to go with PointBlank and say its pretty cool.

[frost vectron]

Ah, that photo explains more.

I hadn't realized that you were using stock darts and that the foam area sealed with the barrel nub. That is a very interesting design indeed. It's similar to nesting brass in that respect, since you have a tight fit around the foam body, but then the dart leaves the barrel nub and then the head is loosely sealed with the 1/2" PVC. Bravo.