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DIY Airgun (Read 10952 times)
Bikewer
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DIY Airgun
Apr 13th, 2011 at 12:25pm
 
I mentioned that I was building an airgun... Here she is!   This is pretty crude, mostly a test-bed.  Still, pretty darned effective.  I've been shooting 1/2" marbles out of the thing and they come out with authority; they will penetrate several sheets of drywall.

Pics of the mechanism:
...

And the whole gun:
...

It's a simple ball-valve, inline with an air chamber made of 1 1/4" pipe with a schraeder valve in one end.   1/2" copper tubing for the barrel.   
I pressurize to 125 psi with a bike pump, only takes a few strokes.
I plan a more complex reciprocating-valve model but I need to get some plumbing parts.
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Curious Aardvark
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Re: DIY Airgun
Reply #1 - Apr 13th, 2011 at 1:22pm
 
lol wow - like it  Smiley

Reminds me of all the blow pipe projects and builds we had a couple of years ago.
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Bill Skinner
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Re: DIY Airgun
Reply #2 - Apr 13th, 2011 at 8:07pm
 
How accurate is it?  And how far will it shoot a marble?  I think it is great, it reminds me of some of the 18th century muskets that used compressed air.  Bill
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Rat Man
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Re: DIY Airgun
Reply #3 - Apr 14th, 2011 at 5:41pm
 
Good stuff, Bikewer.  Any chance of you making a video of the gun firing?
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Bikewer
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Re: DIY Airgun
Reply #4 - Apr 15th, 2011 at 9:57am
 
I do have a nifty little video camera and might give it a try.     Haven't got much of a facility in my back yard for shooting....
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starhiker
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Re: DIY Airgun
Reply #5 - Apr 15th, 2011 at 8:25pm
 
There are hand pumps for precharged pnumatic air guns that can pressurize tanks to over 3,000 psi.  I would be curious to know what pressure your tank can handle.  Is this strictly a mussle loader?  I wonder how easy it would be to get a .50 cal barrel for it?
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Bikewer
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Re: DIY Airgun
Reply #6 - Apr 16th, 2011 at 9:24am
 
The air chamber is just a standard cast-iron pipe nipple....No idea what it's pressure limits are but likely rather high.   Guys working with higher pressures usually use things that are both stronger and lighter.
Mine could probably use a bit more volume, but it does seem to work well.

The copper tubing barrel is in fact nominally .50 caliber, that is the inside diameter.
I was lucky to find some 1/2" marbles... Standard ones are a bit large.   These I found in a goodwill for a buck for the bag...
Other projectiles include darts (made from nails) and AA batteries....

Mine is a muzzle loader but it's pretty easy to make a breech of sorts; you just cut a port in the barrel and insert a piece of close-fitting tubing with a bolt threaded in.
There are several of these up on YouTube.   Some guys have even added laser or telescopic sights.
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Re: DIY Airgun
Reply #7 - Apr 17th, 2011 at 1:48am
 
Thanks Bikewer.  I always liked airguns.  I have a .25 cal Beeman Kodiak(which is really just an imported Webley Patriot) but it has a bent barrel.  I might try my hand at a Do it yourselfer someday.  Yours is inspiring!
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hawk_chucker
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Re: DIY Airgun
Reply #8 - Apr 17th, 2011 at 6:19pm
 
OK I am very impressed. Now go to a gun forum and try to get a reg. stock for it. Since you found the way to build it now just tweek it and have fun!
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Bikewer
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Re: DIY Airgun
Reply #9 - Apr 18th, 2011 at 10:41am
 
One of the YouTube jobs has very nicely incorporated an old military rifle-stock and the result is quite professional looking.... I'll see if I can find it when I get home.
I just jigsawed this one out of a ratty old 2X6 to hold things together and slapped some old black paint on it.  Tactical, right?

What I have in mind to build is a reciprocating valve model with the valve operated by a "poppet" valve.  Most of the ones you see done operate the valve with either a commercial air-tool pistol grip or a simple ball valve.
This releases the "small" chamber and lets the piston open the main charge.
I think a poppet valve would function the same, and you could build a conventional trigger-hammer assembly to operate the poppet valve.
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Re: DIY Airgun
Reply #10 - Apr 21st, 2011 at 7:14pm
 
You might try a large (homemade) Schrader valve next time.  That's what the Girandoni used.  It'll provide multiple shots quite efficiently.

If that's a standard 3/4" galvanised pipe you're using for the chamber, it should (DO NOT QUOTE ME ON THIS, I CAN'T FIND MY CHART) hold something like 2,500 psi before failing, BUT you should only fill it to 1/3 of that for safety reasons (1/3 is the standard hpa airgun margin for error).  Please recheck this before you do it, I don't want a fellow slinger filled with shrapnel on my account.
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Bikewer
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Re: DIY Airgun
Reply #11 - Apr 22nd, 2011 at 9:24am
 
I'd likely work up quite a sweat getting anywhere near 1000 pounds with my bike pump....   Thing goes to 120 in about 5 strokes though due to the small volume.
You see all sorts of things incorporated into these devices; small fire extinguishers are popular, as are propane tanks, the little ones intended for camp stoves and soldering.

I did have an opportunity between rain events here to try some accuracy tests... Shooting at 40 feet with the marbles "patched" with some thin material I put 5 rounds into 2".
That's not bad for a smoothbore, and especially with the very crude apeture sights I made.   I see you can obtain cheap optical sights intended for BB/pellet guns for 15 bucks or less...
I'd have to improvise a mount but it might be interesting.

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Thunder Chief
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Re: DIY Airgun
Reply #12 - Apr 22nd, 2011 at 7:42pm
 
You'd blow out your bike pump way before you reached 1000 psi.  I speak from experience... Embarrassed
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