BBMG project- and pointers?

[Duckford]

Hi, I'm new to the forum, and bbmg's, but not to spud guns or airsoft, and I'm starting out on the latest in a long line of projects.
Most people here will have played CoD , I know I have far too much, and I have basically decided to build a Browning m1919 (bb)MG. Basically, I decided on this style because a)It's a machine gun, and after a little reading I figured this is what thats what bbmg's were designed for, b) because the essentially regtangle body will be easy to make and have space to store any internals parts without afecting the profile. and c) because they were used both as man portable and deployed weapons, which gives me some flexibility with things (I.e. If I fail with what I am hoping to do I can go for something on a tripod that you leave plugged into a scuba tank).
That was too long an intro, but what the heck.
I have most of the things I will need so far, but there are still a few things I am unsure of.
1) Air supply. My original plan was to use a few 1 or 2lb camping propane cylinder, emptied and filled with normal air. I went into the camping shop, and I couldn't tell whether it was possible to refill any of them at all. Any ideas? If not it will probably have to be a 20ozpaintball CO2 tank. Can you fill those with normal air? if so, to what pressure? or would I just be better of to scratch build from copper pipes?
As for pumping it up, how long would you expect one of them to last filled to about 300psi?
2) Where would it be possible to get a 1m long barrel? this may seem a little long, but my plan is to have a 1m length of 40mm pvc(in metrics, sorry) running the length, with the metal barrel running through, and the system set up in a bulpup design (I saw Davidvaini post a bulpup system that is pretty much what I would hope for just 3-4 times as long). Is that a good idea?
Basically, the concept is to have more than enough ammo stored in the barrel, and have a quite large interchangable box mag on the side that will have the gas supply in. Dunno if its ever been done that way around before. Sorry for writing so much without illustrations, I just hope its all generic enough terms for people to understand, as my diagrams I've drawn so far are so poor that even my freind who's an engineer can't read them.

[PaulsAirsoftArmory]

Go to air-sharp.com
You can get plans to make a M1919A4 out of ABS sheet plastic, which is fairly easy to obtain as well as cheap on the internet. You could some up with some sort of propulsion system for it instead of the normal airsoft gun parts.

[jonnyboy]

1.I know propane tanks used on grills are refillable but what fittings you need I don't know. If your going to get a co2 bottle you might as well buy a cheap regulator and use the co2.

What pressure do you plan on using? There's no need to build a copper tank if your using 150 psi or less, just use pvc.

2.Airsoft gi has multiple kinds of airsoft barrels ranging in lengths and inside diameters.I would suggest getting a 6.04 as you use so much ammo you could use lower quality and not worry as much about jams.

Davids bullpup would be fine (it's a vortex isn't it?) but seeing how the browning isn't exactly a small gun you could spread it out more.

[Leonard]

Here's my two cents about the air supply :

C02 would be a much better alternative than repressurized propane tank. Mainly because of the fact that c02 pressure (considering it's regulated) is very consistent and last quite a while for it's size. The reason is because c02 is liquid inside the bottle and evaporates at about 800 psi, so as long as there is liquid c02 in your bottle, you get a constant 800 psi out of it.

A 20oz c02 tank filled with air (it is possible to fill it with air with the use of special fittings that can be bough from palmer's pursuit shop) will give you a short shooting time, not to mention pressure decreasing as you shoot.

[Duckford]

A 20oz c02 tank filled with air (it is possible to fill it with air with the use of special fittings that can be bough from palmer's pursuit shop) will give you a short shooting time, not to mention pressure decreasing as you shoot.

Can't you just have it regulated? The main issue here is being able to fill it up repeatedly, and there are no places to get CO2 tanks filled where I live. I have considered pumping one up with CO2 enriched air (I.e. holding a compressors air intake near a coal fire) but doubt that could work too well. The highest pressure I'll probably be able to get any tank too will be 300 psi (maybe 350-400 if I'm lucky), so that will no doubt cause problems. If I can get 10-20 seconds of good shooting off a single tank I'l be happy, though.
One last thing, though, although I may need more pointers later, does anyone know if wooden vortex blocks work? Due to only being able to build this thing in my school's workshop (under the presumption it will only be a non-firing replica) I've had trouble getting hold of any good plastic or aluminium. Will the wooden block work (even if only temporarily), and where could I get a block of plastic/aluminium to make a better one out of (for free, ideally) if the wood can't take it?
(Pine wood I think it is, it seems sturdy enough)

EDIT: YEah, i've just been looking at the barrels and they all seem to be smaller than the 1m I'me hoping for. Aparently enot everyone shares my veiw that by making something bigger you make it better. I read somewhere that you can use copper tubes from hobby shops, but I went there and the shop assistant had no idea. So, any ideas? if not the biggest I can find is about 65 cm

[Stephen Holliday]

Yes, wooden blocks work. I made 3 bbmgs for my friends, and they are still working. I make mine out of 3, 1/4 in. plexiglass epoxied together. Check out the bbmg starfer forum, and go to MP5, and you'll see my block in the ready to assemble picture.I'm going to make a portable backpack out of 2, 4 in. pvc tanks. I'll put a 12 volt compressor and a cycle battery on it.

[biged]

If you are serious about skirmishing with it, drop in a electric gearbox. A Star249, Wild Monkey gearbox, or an AGM M14 can be fit inside.

Here a picture of my 1919a4 on a Calvary Mk1 emergency response tripod.

This is a demilled gun from WW2. I made the right side plate, tripod, and carry handle. Star249 gearbox inside, V3 hopup, PSG1 length inner barrel.

Pic of the ammo box, SPDT relay with active braking, I can put a large battery in the ammo box, or a mini / lipo in the gun above the gearbox.
http://i70.photobucket.com/albums/i110/ ... 9a4_38.jpg
Tripod folded for easier carrying.
http://i70.photobucket.com/albums/i110/ ... 9a4_39.jpg

///ed///

[Duckford]

Yeah, that was the original idea to electric, but I've got an AEG (TM), and it keeps breaking every time I have the ordacity to pull the trigger. can't really think of many advantages to making it electric, anyway (maybe more shots before needing a gas/battery change), but I liierally want to mow down entire battalions as they charge at me.
Plus, how much can really go wrong with with a BBMG? any problems can easily be fixed, AEG's are all a bit too Rube Goldberg-ish for my liking.
Nice gun, though.

[Hubb]

I'll say this: A standard paintball CO2 tank has ASA threads. It is usually in the form of a brass fitting on top of the bottle. By removing this fitting, you are now introduced to 3/8" NPT threads, which are a more common size. Fill it up and let it rip.

I'll say this, too: Don't expect too many shots from a 20oz tank. BBMGs have a bad habit of consuming buttloads of air. A bigger tank would be ideal. A 5 gallon propane tank would work better and can be tapped (if it is empty, of course) to fit your needs. Still, you would need to consider the air consumption and build the BBMG as efficient as possible (if it is possible).

Now, for a better alternative. It was mentioned before, but I'll mention it again. If you have access to a CO2 fill station, then you should consider regulated CO2. It should last you longer than any other method above and still be portable.

[Duckford]

Can you get CO2 tanks filled where they do fire extinguishers? thats the only alternative, I live at least a short flight away from any paintball sites.
Alternatively, does anyone have experience with homemade CO2 pumps? theoretically it can be done.
And do CO2 cylinders need regulating? probably a dumb question, but hey.

[john bunsenburner]

Well duck, you can most probably get refills for a fire extingisher where you buy them but you will need some kind of excuse. And makign a CO2 pump is a fairly stupid idea, as CO2 is more dense than air and it would be just as easy to buil an air pump(also for high pressures) which would give oyu better shots velocity wise compared to CO"(and i am not even going to get started about the hug eprice difference between using free air and makign CO2).

[Duckford]

Making co2? whack the pump intake near your exhaust pipe and drive to work!

[john bunsenburner]

That isnt worth the effort as air is better and cheeper, CO2 is jsut useful because of its availability!

[Duckford]

so air is better or CO2 is better? I'm a little lost here

[Brian the brain]

Air is better.

But compressed CO2, such as found in paintballtanks, is easier to come by.For a reasonable price anyway.