Semi-auto 800 PSI .51cal WIP

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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Gun Freak
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Wed Mar 28, 2012 4:03 pm

How do you figure?
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JDP12
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Wed Mar 28, 2012 4:04 pm

I don't see how that would do anything.. the mag block has female threads so that would make it even worse. These are NPT threads, not BSPP so I can't thread them infinitely.
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JDP12
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Thu Mar 29, 2012 10:31 pm

Got the brass elbows today.. they were pricey but after assembly, definitely worth it. It may not look like much, but it definitely compacted the gun a significant amount in my opinion.

Finally got bolt dimensions worked out, so ramses will be making that for me this weekend and shippin it here.

Still alot of work to do, stay tuned for updates!!

Also, the caliber is like .51 now.. not .625.. it never actually ended up being that, so I guess i could change the title.
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jackssmirkingrevenge
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Fri Mar 30, 2012 12:59 am

Glad you sorted the machining out "locally" :)
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Crna Legija
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Fri Mar 30, 2012 1:00 am

with the method i said you can grind the female threads done so theres only 3 or so and cut a peace of all thread so it sits very low.
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JDP12
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Fri Mar 30, 2012 11:38 pm

Yea ramses is machining for it me here in country.. thankfully.

Ran into another issue... Chopping up a nerf gun for the handle and trying to figure out its placement.

All the yellow part will be cut off, it'll pretty much just be the black portion of the handle. I was originally hoping to tuck it right behind the lower brass elbow, but theres an issue: the magazine would get in the way. So i'm looking for solutions. I could put it right below the chamber, but then the gun would be like 10" tall, which is absurd. So I pretty much need to slap the top of the handle to the bottom of the upper pipe.

Here are my potential solutions:

1) I could reverse the chamber. This poses a few problems: a), i'd have to shorten the chamber, b) the handle would be a bit too far forward: It would probably have around a 16" LOP.

2) I could rotate the whole gun 90 degrees so the chamber is horizontal, however then the gun would be something like 4" wide.. which is pretty wide.

3) I could simply move the mag block slightly further back. This is probably the best option as it'll negate all the drawbacks of the first two options. The ONLY negative is that it will probably increase dead space to almost 1 in^3. While I despise and loathe dead space with all my heart, GGDT only predicts a drop of 6-10 fps muzzle velocity due to the high pressure.

So after analysis, i'll probably just have to move the mag block back. Yea i'll have more dead space but its probably the best solution.

Any input is appreciated.
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Sat Mar 31, 2012 2:40 pm

Wow man it looks so much better now!! :D

I agree the third option is the best. But I too hate dead space with a burning passion. You will do this by lengthening the close nipple on the barrel port of the piston valve, correct?
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JDP12
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Sat Mar 31, 2012 3:16 pm

haha yeaa it does look better.

yea i'll have to lengthen it. that close nipple is actually epoxied into the bushing, so i'll probably have to add a coupling+ nipple, or i'll use a female x male adapter. depends on how much room I need to add. Looks like I'll have to add 2-3". Gonna cut down on the dead space by epoxying in a section of barrel tube into the 1/2" nipples so its not as much, but it'll still add up a bit. Dead space sucks.. but i have to do what I have to do.
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Sat Mar 31, 2012 4:32 pm

I never understood why people epoxy threaded fittings... :roll: is it because of the way you made the seat? Anyways, don't add a coupler or a male-female, that wouldn't look as good as a longer nipple... If forcing that close nipple out won't damage the seat, I would do that.
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JDP12
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Sun Apr 01, 2012 12:41 pm

It's due to the way I made the seat.

Filled up the handle with epoxy to give it a bit more sturdiness.

Gonna start working on the trigger apparatus today.
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Gun Freak
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Sun Apr 01, 2012 12:56 pm

Ok so if you do couple it to another nipple, use a brass coupling because the galvanized ones aren't straight.

Also, is it me or is the slide valve crooked?
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JDP12
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Sun Apr 01, 2012 1:03 pm

Nope its not you. When I drilled and tapped the hole into the 3/4" endcap at the back of the piston valve, it wasn't perfectly straight.
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JDP12
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Mon Apr 23, 2012 7:28 pm

Update..

finally got the sections cut out of the barrel for the mag input, air input, and bolt handle.

Now i have to figure out why the piston valve is leaking...
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warhead052
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Mon Apr 23, 2012 7:42 pm

Wow, looks good. Are you going to use actual bullet casings to hold your ammo?
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JDP12
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Mon Apr 23, 2012 7:45 pm

nope. right now I don't have plans for ejection.. so it'll just be solid ammuntion.

I'm tryin to figure out how i might upgrade to ejecting cartridges eventually.
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