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Semi Auto

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: PVC Arsenal 17 » Tue Jan 05, 2010 10:27 pm

@POLAND_SPUD: Interesting valves you linked to there. I'll have to check those out. As for the MJVO-3, I've only used it at 120 psi and it was easy to open. Earlier in this thread Solar said he's used Clippard MJ Series valves at 700 psi. Might want to ask him.

And good luck with your project, Lockednloaded. Just something to keep in mind- if you're using this thing for paintball or if you plan on carrying it around pressurized, using all metal parts is a very good idea. Pressurized PVC pipes like to burst when they hit things. Safety First.

You'll especially want to consider using metal parts if you decide on a propane or co2 rig as the gasses will chill the gun down and make it brittle. Very unsafe for plastic.

The co2 rig gets my vote of course. I suggest buying a Palmer's Stabilizer (regulator) once you save up enough. A standard paintball co2 tank will thread right into one of these and you get an 1/8" NPT output port to connect your gun to. Depending on the spring kit you choose, you can regulate the output pressure to between 0 and 900 psi with respectable accuracy. I own one with the low pressure spring kit (0-300 psi) and I highly recommend it.
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Last edited by PVC Arsenal 17 on Tue Jan 05, 2010 10:39 pm, edited 1 time in total.

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Unread postAuthor: POLAND_SPUD » Tue Jan 05, 2010 10:31 pm

it depends what do you mean by 'large chamber' and 'a few good shots'... :wink:

you can either:

-use co2 or HPA tank with a reg (but that'll be the most expensive route)
-use air and store it in a large capacity tank (could be practical if you use an empty propane tank/ cylinder (those large ones))
-use unregged propane

the last one is the best option IMO opinion as you could get the most shots out of it...
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Unread postAuthor: Lockednloaded » Wed Jan 06, 2010 7:25 pm

by "large chamber" i mean two feet of 2" pipe, and by "a few good shots"i mean anywhere from 3-6 shots that go about 100-150 yards. I like the propane idea, but propane smells awful (I know its supposed to do that for leak detection) and i was not aware i could get so many shots with propane
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Unread postAuthor: Lockednloaded » Thu Jan 07, 2010 9:54 pm

I'm sorry to double post, but I have an Update on my progress. I have recently come into possession of a large fire extinguisher that is about a foot and a half long (or about half a meter). Since most of my semi-auto plans were shot down, i decided to go with a regulator setup. co2 is too expensive atm, but I think this will work great. I am going to put This regulator on This full-metal chamber (see below) it will be pumped up to 200psi and incorporated into some sort of stock, or backpack(its just a little to big to put on a belt).
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Unread postAuthor: PVC Arsenal 17 » Thu Jan 07, 2010 10:32 pm

Did you check to see what type of threads are on the cylinder and what adapter (if any) you will need to get NPT threads? I'm not sure what threads fire extinguishers typically use. I'm sure someone on here knows, but even then it's probably the type of thing that varies from manufacturer to manufacturer.
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Unread postAuthor: Lockednloaded » Thu Jan 07, 2010 10:35 pm

no, all i know is that it just barely can't fit 3/4 sch 40 pvc threads, but do you think it will work well for my design, and if not ive made a new one that might not need constant air from a compressor or other source
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Unread postAuthor: PVC Arsenal 17 » Thu Jan 07, 2010 10:44 pm

If it can safely hold pressure, I don't see why not, provided you can find a way to adapt the threads. Is it heavy? The weight might bother you, but personally it wouldn't matter to me. It can only make you stronger right? :lol:
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Unread postAuthor: Lockednloaded » Thu Jan 07, 2010 10:51 pm

edit
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Last edited by Lockednloaded on Wed Feb 10, 2010 9:48 pm, edited 3 times in total.
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Unread postAuthor: PVC Arsenal 17 » Thu Jan 07, 2010 11:10 pm

I'm not sure I understand what's going on there. Why do you have 2 connections to the chamber?
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Unread postAuthor: Lockednloaded » Thu Jan 07, 2010 11:18 pm

whoops i'm sorry that second connection is just supposed to support the valve so that it does not bend or break, i probably should have specified that :oops: in the notes, but any way, the second connection does not hold air
my mistake sorry
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Unread postAuthor: PVC Arsenal 17 » Fri Jan 08, 2010 6:48 pm

Well I don't see the need for a slide valve in this setup. I would use a blowgun or a ball valve.

Since it's no longer semi auto (right?) I'd say forget the magazine/hopper. The design you have for that would not work anyway because there is nothing to seal the breech opening. Unless you capped off the magazine, backpressure would simply push the stack of balls out of the hopper and the ball you intended to fire would hardly go anywhere. Even with a capped off magazine, you'd have to ensure that no backpressure can leak around the ball about to be fired. You'd lose some performance there.

Either stick to good old muzzle loading or reconsider a breechloading design. I'd suggest cutting out a section of the barrel to drop in rounds one at a time, and to fire, cover the open section with a sleeve.

Better yet, just buy this.
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Unread postAuthor: Brian the brain » Sat Jan 09, 2010 10:38 am

haha, yep the sticker said it was a co2 type so it should hold atleast 200psi


Co2 is commonly stored at around 850 psi.Burst pressure should be around 3000 psi...so I think it will hold 200.
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 10, 2010 4:03 am

Brian the brain wrote:Co2 is commonly stored at around 850 psi.Burst pressure should be around 3000 psi...so I think it will hold 200.


Our CO<sub>2</sub> fire extinguishers at work are rated to almost 4,000 psi, I would think 200 is safe :)
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