Airsoft Detent BBMG

[Gun Freak]

First, this is in the discussion because it isn't complete. When it is all finished I'll post it in the showcase. Trust me, it will look cool.
Anyway, here are the specs.
Chamber: 11" of 3/4" pvc.
Barrel: 3' 6.35mm aluminum
Detent: 2 o-rings max, although most of the time I will probably only use one because it is really tight. I don't even know if the bb will be able to make it through. We'll see tomorrow after the JB is fully cured.
Valve: 1/4" ball valve on my FE tank for testing. May add a new valve in final version.
Running pressure: Will depend on pop pressure of detent, but anywhere up to 180 psi.
QD in rear of chamber for connection to air supply.
Pictures:
Tank

With barrel

With tank

Barrel assy

Detent seat

With o-ring

BB with detents.

Sorry about blurry close ups, macro wasn't cooperating You should get the idea though.

Suggestions are appreciated, this is a WIP.
:occasion5:

[clemsonguy1125]

Im afraid the bbs wont make it through, Polandspud had a detent about that size and it took 300psi. You could cut a groove in the pipe and jb weld the oring like that or even better wrap tape over it and you can replace it. Other than that, it looks good.

[Gun Freak]

If the o-rings don't work I can just switch to tubing which was my original plan, but I couldn't find the right size so I used an o-ring. My plan C however for this would be take off the brass tubing, drill out the back and put the o-ring behind the bushing, hard to explain but it might work. Or I could drill out the o-ring a bit, we'll see how testing goes tomorrow. It was easy to push the bb through the o-ring when it wasn't in the pipe and had room to strech, but the brass pipe is limiting how much it can strech so it is going to tank a lot of force to get it out.

[jhalek90]

i can tell you right now that 180 psi will not push the bb through.

I had to use an oring the the bb ALOMST fell through before it popped at 100 psi... my set up was very similar.

[Lockednloaded]

You could calculate this before just going gung-ho into testing.

All you would need to do is figure out how much force is needed to push the BB through your seal. Then, to find the psi it will take to push it through you just do pressure * ~1/2" the surface area of the BB (assuming only half of the BB's surface area is embedded into the seal)

[c11man]

[quote="Lockednloaded"
All you would need to do is figure out how much force is needed to push the BB through your seal. Then, to find the psi it will take to push it through you just do pressure * ~1/2" the surface area of the BB (assuming only half of the BB's surface area is embedded into the seal)[/quote]

you would calculate it with the cross secton area of the bb. the only time you would have less area is when the bb is right in the middle of the oring and after(after doesnt matter becuase its already throught). when its in the middle the oring might deform around the edges of the bb but it would affect the area very little.

[jackssmirkingrevenge]

Looking good, it will take some trial and error but the benefits of a detent will make it worthwhile

[lozz08]

JSR is right. Like me, you'll probably accidentally come across some fitting that does exactly what you want. That o-ring certainly won't.

[Gun Freak]

Well testing today confirmed my nightmares
The bb held strong in the breech up to 160 psi. My pump is not cooperating I'm either going to get a new head for it or send it back. I could have used the money on a HS camera. Anyways, I tried all these different things, don't feel like saying them all lol. I can push the bb through with my fingers but it is really hard. Pushing it almost half way through gets it far enough to where to pressure can force it out, but only for one shot before I have to do it again. I don't really know what to do now, besides maybe trying rubber tubing, so I need some more suggestions. If all else fails, I'll use POLAND SPUD's adjustable detent. I think my current setup will allow it.

[c11man]

use a very small file and take out some of the rubber on the inside of the oring, using trial and error take out more and more rubber untill it pops at the right pressure

[Gun Freak]

That's what I was thinking about doing. I'm gonna go try it not, but I don't have any files so I'll try like a drill bit or something.

[lozz08]

If you take a look at my mag fed 6mm thread, you'll see that I used a compression fitting designed to clamp over compressor line to go into a blowgun. If I were you, I'd go purchase this:

http://cgi.ebay.com.au/BRAND-NEW-High-P ... 588a5e8f17

It comes with the compression fitting that I used and its inside diameter when not screwed in is exactly 6mm. When you screw it into a 1/4 inch nipple, the washer is squashed. You can set the popoff pressure to whatever you like. And the pressure washer handle is really good quality. They sell heaps of them, get one in a buy it now auction.

[Gun Freak]

That's Australian, and it is a lot of money. If the method I am using proves to be dysfunctional, I will switch to the threaded fitting washer sandwich method thingamabober. Thanks for the suggestion though Lozz.

[Gun Freak]

New videos, got it working. Power is good. It gets through 5 layers of cardboard and my 300 fps pistol can't even get through one. That is pretty strong. Thing is, ROF is still high, and that is what I wanted to lower. I'm gonna mod my other o-ring and see what I can do.
[youtube][/youtube]
[youtube][/youtube]

[lozz08]

Sir, you will never lower the rate of fire of a bbmg vortex to a reasonable level. The fact is that the only way to lower ROF is to lower the flow of gas coming from the blowgun. But vortex blocks need high flow to agitate bbs.

That is the whole point of what I did with my 6mm mag fed full auto. I suggest you check it out because it allows for a lot of adjustability of rof and power. I have nearly finished the outside of the gun and when I post it in the showcase It will give you a good idea of what a detent type system can do in airsoft.