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BBMG air sources

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Unread postAuthor: jimmy101 » Tue Jun 04, 2013 3:16 pm

jackssmirkingrevenge wrote:Given the way BBMGs work, you could probably use 275 psi directly in an appropriately rated PVC tee, just maybe add a pop-off valve for safety.
Or instead of a pop-off, use a regulator between the gas source and the BB chamber. If you don't want the chamber above 100 PSI (for PVC) then set the reg to that pressure. The reg should be very close, if not directly mounted on, the chamber. This would require a reg with pretty high flow.

As Jack suggests, most BBMGs are flow restricted. The gas source pressure is much higher than the chamber/barrel pressure since you can't flow gas fast enough to get the chamber/barrel up to the source pressure. A 125 PSIG gas source, through 25' of 3/8" ID hose, then a blowgun valve, then through a several in^3 chamber, then a couple feet of 0.18" ID pipe gives chamber/barrel pressures of only about 20 PSIG. And that only when a BB is actually in the barrel, when the barrel is empty the chamber pressure is even lower.
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Unread postAuthor: nicksam112 » Tue Jun 04, 2013 3:49 pm

So what you're saying is that I'd have to run a much higher pressure than I'd think in order to account for all the extra volume given by the hose + chamber?

So then I'm assuming something like a 400 psi source through some pipe and in a relatively large chamber would be fine then?

If that's the case, there are 40 dollar paintball regulators that either do 300 psi or anything from 450-800 psi. That seems to be pushing it pressure-wise but I don't know much about these systems so any input would be greatly appreciated.
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Unread postAuthor: jackssmirkingrevenge » Tue Jun 04, 2013 4:00 pm

You should always assume the worst case scenario, where a BB jams in the breach and the BB chamber reaches the full pressure that your air source is outputting. That being said, small bore thick walled PVC can take such pressures.

I've even used PVC for hybrid cartridges, this held well at 6x, more than 300 psi:

[youtube]http://www.youtube.com/watch?v=w8MZ5aS2-JA[/youtube]

Or instead of a pop-off, use a regulator between the gas source and the BB chamber. If you don't want the chamber above 100 PSI (for PVC) then set the reg to that pressure. The reg should be very close, if not directly mounted on, the chamber. This would require a reg with pretty high flow


Valid observation, my suggestion here was to avoid the complication and expense of a regulator.

What do you plan on shooting, airsoft or metal BBs?
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Unread postAuthor: nicksam112 » Tue Jun 04, 2013 4:15 pm

I plan on shooting airsoft bb's since they're readily available from the nearby Sports Authority. They're the cheap crappy 0.12 ones but if I'm going through bb's that fast, quantity becomes a quality of its own haha

I guess at this point it just seems easiest to go with the regulator Gippeto suggested. However they charge an extra 15 bucks if you want to allow it to accept up to 3000 psi.

It's either that or go with a Ninja Paintball regulator that brings it down to 300 psi then have some kind of pop off valve right before it enters the actual chamber just for safety's sake
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Unread postAuthor: jackssmirkingrevenge » Tue Jun 04, 2013 4:22 pm

Beware of using BBs that are too cheap, they will be more likely to jam if they don't have a regular shape, and all it takes is one to ruin your day.

I would be happy feeding 300 psi into a BB chamber made of 1" PVC schedule 40 or 80 fittings (with burst pressures over 1000 and 2000 psi respectively) as long as a 150 psi pop-off valve is fitted to the chamber. In normal use, because so much pressure is lost to expansion in the chamber, you will never reach 150 psi if you're feeding 300 psi.

It's worth looking at this thread in order to get all the parameters right: http://www.spudfiles.com/forums/dvs-off ... 18159.html
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Unread postAuthor: nicksam112 » Tue Jun 04, 2013 4:33 pm

That burst pressure site is great, thanks for that useful info!
Thanks for all your guy's help, I think I'll just go with the Ninja Paintball regulator then.

Hopefully I can report back with some kind of results in a week or two.

One more quick question, do you happen to know the threads paintball tanks use? I'm looking to adapt the line to a 1/4" NPT so it's easier to work with and find threading/valves for.

EDIT: Ignore the last paragraph, I just found out there are adapters that adapt it to a 1/8" NP thread which should be suitable

UPDATE: In case anyone has been following this thread, I've found a paintball regulator which can allegedly regulate the pressure all the way down to 50 psi and is completely adjustable. I'm a bit skeptical as it's the only regulator like this that I've found and it seems relatively cheap. However it has no reviews. Link here: http://www.amazon.com/gp/product/B0046V ... L5NBD9F8JW

Any input would be greatly appreciated. Thank you!
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 05, 2013 12:38 am

I can't speak for the rap4 model but I had got one of these in similar configuration and it was complete crap, ruined one of my pressure gauges and almost blew up a chamber.

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I would expect something sold by a reputable firm to be of better quality though.
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Unread postAuthor: anarchy08 » Sun Jun 16, 2013 3:59 am

I can actually vouch for that style of regulator jack, though only at the lower end of the scale up to 350 psi from unregulated.

I have one on my semi auto 6mm M16 and on my .50 cal 19 shot bolt action marble rifle. Iv been out of the game awhile (pyro's too addictive) but should post my finished weopons
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