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BBMG: propane powered! help

Posted: Fri Jul 31, 2009 9:56 pm
by spudnutbutthut
I am new to making BBMGz and need a bit of help with my parts list. I am a cheapskator when it comes to buying stuff for pvc guns. I want to make a cloud BBMG for airsoft suppressive... overpowering fire.

I want to find a good regulator for C02 tank for my BBMG or a way to use propane coleman cans like airsoft gas guns use.

I want the regulator to be like $40, so if you know where i can get one itd be great!

BTW how much PSI do you need to run a cloud shooting .2s at like 350 fps?


sum it up:

i need;

a regulator cheap

or

a way to use propane for myy BBMG

Im typing with a wii so be understanding :)

Posted: Fri Jul 31, 2009 11:42 pm
by frozebyte
Are there any designs you're looking at from the showcase? :)

Posted: Sat Aug 01, 2009 6:54 am
by spudnutbutthut
yea i went back and looked at some of the designs, I'm intersted in making just a cloud that would eventually fit into a browning.30 cal or an MG34, I REALLY WANT TO USE PROPANE! If anyone knows how to make it work with propane id be greatful.

Re: BBMG: propane powered! help

Posted: Sat Aug 01, 2009 7:25 am
by Ragnarok
spudnutbutthut wrote:BTW how much PSI do you need to run a cloud shooting .2s at like 350 fps?
You might as well ask me "How many horsepower do you need to get from 0-60 mph in under 5 seconds?"*

There's missing information in the question. In your case, barrel length, barrel tightness, cloud chamber volume, actual regulator flow... all of these things change muzzle velocity in a cloud.

It's not impossible to get these things to work with propane, but it is trouble, because it draws off pressure very fast, thus causing tank temperature to drop dramatically - thus losing pressure.
I recall seeing one that did work (although I think it was a vortex, the basics of the gas system are identical) in the old archives of either here or Spudtech, but I can't immediately find it. There are however still all of those references to problems which I can find.

*The answer by the way, is none.** I just lob you off a tall building, and you'd be doing 60 mph in under 3 seconds.
** To the pedantic - shut up.

Posted: Sat Aug 01, 2009 7:25 am
by spudtyrrant
unfortunately propane tanks don't deliver enough flow unless you have a pretty large expansion chamber and are only firing shots in burst seldomly.

Most likely your not going to find a good reg for under about $80 I suggest this one http://cgi.ebay.com/Palmer-Nickel-Fatty ... dZViewItem it works on co2 hpa and nitrogen so your have your pick.

It also has a 400psi max output in case you want to use it on any future projects. for this reg you will have to get a hose from a paintball shop and splice one end and have a hydraulic shop clamp an npt fitting on but with this reg and a 20 ounce tank you would be shooting for a while.

I would also get a lower output valve for the bbmg so your supply last longer, and i would run about 80 psi during your games if you don't want to hurt anyone lol

Posted: Sat Aug 01, 2009 7:37 am
by inonickname
Propane is basically unsuitable for this purpose. The only reason gas pistols can use it because they are more efficient and require less gas. However, strafers tend to be highly inefficient. (in terms of flow requirement).

CO2 works, but you should fire in bursts to prevent freezing your bottle.

Kobalt regs have been used for this purpose, and palmers stuff is brilliant.

The psi you use for a certain velocity is highly dependent on many factors..build the gun, then use a chronograph and tweak the pressure to suit. Also remember to account for cooling of the gas/liquid.

Several basic mathematical statements say that there will only ever be 1 round in the barrel at the time (ignoring muzzle breaks, silencers etc) so a longer barrel will equal a slightly lower rof. However, don't expect it to be much. A longer barrel will also give more accuracy (who cares? it is a machine gun after all) but most of all more velocity for the same pressure.

You could also upgrade to a vortex block for more reliable feeding and efficiency.

Posted: Sat Aug 01, 2009 10:33 am
by spudnutbutthut
so there is no way i can have a bbmg for under like 200 bucks?


;(

Posted: Sat Aug 01, 2009 10:37 am
by inonickname
Yes, use a compressor or be extremely trigger friendly.

Propane will work, though as it expands it cools- and the pressure drops off. After a short amount of firing, the pressure will be too low to be effective.

If you made something that kept the tank temperature constant-like a thermostat it could be usable.