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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.
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Xamllew
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Fri Nov 27, 2020 3:43 pm

PracticallySane wrote:
Wed Nov 25, 2020 6:20 pm
I'm shooting 360 grain slugs at the moment. At 1800 psi it shoots clean through 2" plywood. No hesitation at all. At 3000 I feel like it could drop a grizzly bear. A chronograph is pretty high up on my list but currently I dont have any actual number for performance.
Madness. Can't wait to see a vid of this beast in action.
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Tue Dec 01, 2020 1:44 pm

PracticallySane wrote:
Wed Nov 25, 2020 6:20 pm
A chronograph is pretty high up on my list but currently I dont have any actual number for performance.

you may use "chrono connect " app from google play , it is pretty accurate !
come undone
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Tue Dec 01, 2020 7:37 pm

Mr. JSR talked me into picking up one of these things. $28 delivered. It did not realize how small it is, this thing is tiny. I hope the muzzle blast doesn't destroy it. 😬. Fingers crossed, this weekend i will do some more shooting. Cant wait to see some numbers.
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jackssmirkingrevenge
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Wed Dec 02, 2020 7:12 am

That was quick! Someone kindly translated the Chinese manual to English:
Speedometer Manual Tripod_Revised.pdf
(116.33 KiB) Downloaded 29 times
Unlike what I initially thought, it seems it can indeed store up to 40 shots and give muzzle energy readings up to 800 joules (for a projectile weighing 0-10 grams).

Curious to see your results, still figuring out mine with something more hardcore. I got some weird results so far:

FX Streamline 0.22" with 200 bar fill and JSB Jumbo Heavy 18.13 grain pellets.

Power Level II - 210, 210, 213, 211, 211 - average 211

Power Level III - 204, 207, 207, 205, 208 - average 206

This gives and average of 692 fps / 19 ft lbs for the medium power setting and 676 fps / 18 ft lbs for the high power setting.

I haven't compared it to another chrony yet but something is definitely off, fired into the same piece of plywood the base of the pellet is about 4mm from the surface at medium power and 8mm at high power, so it's impossible that it's shooting slower.

It's also well below the expected power level at high power which for this pellet should be in the region of 900 fps / 33 ft lbs.

I suspect that the medium power readings are correct and the muzzle blast is throwing it off for the high power.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Wed Dec 02, 2020 6:44 pm

I got off a little early today. I decided to play with the chrony a little bit to see if I experience the same as JSR.

I recently picked up a "beeman comander .22" its a incredibly priced PCP rifle.

I ran a string of 10 shots (only one power level)

Every shot was between 274 and 279 M/S came out to roughly 915 ft/s with crossman premier 14.3 grain makes 26lbft of energy. Right on the money.

The gun came with a built in sound moderator, I wonder if it is catching the gasses before they can interfere with the reading?
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Wed Dec 02, 2020 9:29 pm

PracticallySane wrote:
Wed Dec 02, 2020 6:44 pm
The gun came with a built in sound moderator, I wonder if it is catching the gasses before they can interfere with the reading?
I tried again at high power with the muzzle 7 inches away from the first sensor and now it seems to be making sense.

I got this 5 shot string in meters per second: 258, 262, 260, 260, 259 for a 259.8 average.

This translates to 852 feet per second and 29 ft lbs which is much closer to what I was expecting.

I will compare it to a "proper" chrony soon to see if that is the case.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Thu Dec 03, 2020 4:12 pm

When I chrony my cannons, I have to have the chrony about 10 to 15 feet away from the muzzle, or else the gasses pass over the chrony first and give readings of over 2000fps.
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Thu Dec 03, 2020 7:46 pm

Unfortunately these things are so small it would be very difficult not to shoot the chronograph itself or miss entirely at those distances.

But I do believe it is directed at airsoft and other low power toys so I'm not complaining. We will see what happens this weekend. I am going to try to get up some videos.
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Sun Dec 13, 2020 3:09 pm

So a little update, I did a little shooting. At 1000psi I got 586 fps. Roughly 275ft/lbs.

At 3000 I launched the chronograph across my drive way and I to several pieces... so not real performance data.

How ever in the never ending quest of moar-power I have assembled a hybrid out of nearly identical components. I am going for a full on CLGG. I could use some input on this one.
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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Tue Dec 15, 2020 7:38 pm

PracticallySane wrote:
Sun Dec 13, 2020 3:09 pm
At 3000 I launched the chronograph across my drive way and I to several pieces... so not real performance data.
Thank goodness for cheap chronys.... did you get it on video at least?
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Wed Dec 16, 2020 3:28 pm

Unfortunately I did not. I know you guys want videos! I am here in Colorado and we have snow at the moment... we should have some nice weather coming up. Maybe this weekend...

I have switched over to my hybrid though. As far as I am concerned this thing is complete, a smashing success.

I even replaced the cast iron!
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hectmarr
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Sat Dec 26, 2020 11:47 am

La operación es lo que llamo una válvula de carrete opuesta a un pistón debido al hecho de que estoy usando sellos oring en lugar de un sellado...
I have a couple of questions for you.
How does the piston seal work, with o'ring and you don't use a front seal? :roll:
How many shots does the air tank that you see in the photos last? or should you pump air with every shot?
I am the author of the first semi-automatic hybrid, check this out :shock: ...viewtopic.php?f=28&t=26676
And of the hybrid that can shoot in the shortest time: :shock: viewtopic.php?f=28&t=27190
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Sat Dec 26, 2020 12:39 pm

The "t" fitting that I use is a "street t" so it has one set of male pipe thread. The front of the piston sits inside the male threaded portion of the fitting. The back of the t has a 3/4-1" male to male reducer. The back of the piston sits in the 1" portion of the reducer. With out the reducer the piston would be balanced and would not fire on pressure differential.

Unfortunately this configuration only gets one shot per fill.. and with a hand pump 3000psi is a workout.

The guns performance is spectacular. The pilot volume is incredibly small. The trigger mechanism i created functions with a crisp "release" and it fires with a sharp bang.

I made A piston hybrid that uses this same piston/valve configuration. I like that it has a very small footprint.
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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hectmarr
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Sat Dec 26, 2020 10:06 pm

I understand halfway ... sorry. :( Do you have a simple drawing? ;) if you don't mind, so that I understand the concept of the valve? I mean, not to use a seal on the face of the piston pointing to the combustion chamber, (hybrid), or to the firing air chamber, pneumatic).
I am the author of the first semi-automatic hybrid, check this out :shock: ...viewtopic.php?f=28&t=26676
And of the hybrid that can shoot in the shortest time: :shock: viewtopic.php?f=28&t=27190
PracticallySane
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Sun Dec 27, 2020 10:27 am

Does this make any sense? Art is not a talent I have...
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I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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