Yet another QEV and 3/2 valve cannon

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
Xenophile
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Sat Sep 19, 2020 6:09 pm

Overview of FS resized.jpg
My latest creation. As the title suggests, I using a QEV and 3 position 2 way valve with a 300 psi input from a regulated HPA paintball tank. I have two different barrels, one for 3/8 inch (9.5 mm) steel shot and another for .30 caliber steel shot. The 3/8 inch barrel is currently muzzle loading, but I plan on eventually installing a breach like the one I made for the .30 barrel. The projectiles are held in place with neodymium magnets before firing. The stock is made from some cheap pine that I stained with a polyurethane stain. Eventually I plan on making an integral tubular magazine for the .30 barrel from a "T" fitting.
Ballistics gel test 2.jpg
This is a test using some homemade ballistics gel. I made a 4 Liter block with a standard 10% mix. The 3/8 in shot went in 7 inches and the .30 shot went in 5 inches.

Overall, I'm very happy with this build. I'd love to hear your thoughts!
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jackssmirkingrevenge
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Wed Oct 07, 2020 4:04 pm

I love the look, and good performance too! Always nice to see people pushing the envelope when it comes to pressure.
hectmarr wrote:You have to make many weapons, because this field is long and short life
Xenophile
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Thu Oct 15, 2020 5:46 pm

Thanks JSR, I'm glad you like it!
I've completed a gravity fed magazine ( 10 shot capacity for .30 caliber shot) which is working fairly well, but I am having some issues with double feeding.
Air gun overview .jpg
I'm using a "detent" system with neodymium magnets to keep the shot in place, but this seems to be unreliable. Anyone here know of a good way to construct a magazine (or other device) to minimize double feeds and improve reliability?
Air gun accessories .jpg
I also got another picture showing the completed cannon with all accessories. This gun continues to be an absolute blast to shoot, and gets fairly good gas efficiency. I get around 50 shots from a tank filled to 100 bar (1450.38 psi).

Still to come is a breach for the 9.5mm barrel and maybe a suppressor, although it's only slightly louder than a traditional pellet rifle. Maybe better optics than my hastily crafted laser?
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jackssmirkingrevenge
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Fri Oct 16, 2020 8:44 am

Xenophile wrote:
Thu Oct 15, 2020 5:46 pm
I'm using a "detent" system with neodymium magnets to keep the shot in place, but this seems to be unreliable. Anyone here know of a good way to construct a magazine (or other device) to minimize double feeds and improve reliability?
One idea would be to have a pressure actuated element that physically blocks the next projectile in the magazine, here are some rough ideas I had sketched:

Image

Image

A spring-loaded detent might also do the trick, it's what my Brazilian Fionda uses and it works quite well, no double feeds.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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