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2.4kpsi helium powered BB gun - build log

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: ALIHISGREAT » Sat Jan 05, 2008 6:06 am

Due to the lower projectile mass, the barrel which is at least .006" too big, and the fact that the planned setup prevents me from using a hop up, I don't expect accuracy much better than that of a musket, if at all. If you read the figures I quoted though, ammo consistency will be higher than that found in conventional firearms, what with the 1/10,000" tolerances and all.


hmm well 0.006" is like 0.15... mm which isn't really that much but i suppose this could affect the accuracy quite alot. but firearms with their 1/10,000" tolerences can shoot 500yards + accuratly (assault rifles) and 2000 yards accuratly for some sniper rifles so i think asking 100-150yards maybe even 200yards accuratly isn't so ridiculous.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 06, 2008 2:19 am

If you made a strafer, you'd get a much higher hit probability at long range (let's face it, with 400 psi and a barrel less than 2 feet long I got 650 feet per second for 4.5mm BBs, just think what you could do with 6 times the pressure!), I would still consider that option if I were you.
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Unread postAuthor: ALIHISGREAT » Sun Jan 06, 2008 5:10 am

jackssmirkingrevenge wrote:If you made a strafer, you'd get a much higher hit probability at long range (let's face it, with 400 psi and a barrel less than 2 feet long I got 650 feet per second for 4.5mm BBs, just think what you could do with 6 times the pressure!), I would still consider that option if I were you.


a tungsten carbide bb shooting strafer :twisted: that would possibly be the most awesome thing ever 8)
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Unread postAuthor: Carlman » Sun Jan 06, 2008 5:21 am

hmmm lets see, 50 bbs per second, $15 per 5 bbs, thats around about $150 PER SECOND OF SHOOTING!!!

Im just assuming here, correct me if im wrong, that he WONT be making a strafer to shoot tungsten carbide bbs unless hes frigin rich!! lol

But yea a strafer with that psi behind it with steel bbs would be an awsome sight to behold and bask in all its glory, mwa ha ha :twisted:
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 06, 2008 5:27 am

Heavyweight airsoft BBs at close to mach 1 would still be an awesome sight at that rate of fire ;)
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Unread postAuthor: Carlman » Sun Jan 06, 2008 5:30 am

ooo i just had an awesome daydream, a supersonic strafer, it would be like continuous sonic booms :D
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Unread postAuthor: ALIHISGREAT » Sun Jan 06, 2008 5:49 am

jackssmirkingrevenge wrote:Heavyweight airsoft BBs at close to mach 1 would still be an awesome sight at that rate of fire ;)


hmm that would dish out one hell of a lot of power if you think about how many would be hitting almost at the same time and how powerful they would be :twisted:
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 06, 2008 6:17 am

Using 0.43 gram BBs at 1,000 feet per second, which is very realistic in my book for the pressures and barrel length DYI is planning on using, you'd get just under 15 ft/lbs of muzzle energy per BB - this means that coupled to a cloud's awesome rate of fire, you'd get the performance of a 22 rimfire automatic at close range in terms of weight of fire :shock: :D

(hint hint DYI ;) )
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Unread postAuthor: ALIHISGREAT » Sun Jan 06, 2008 7:47 am

jackssmirkingrevenge wrote:Using 0.43 gram BBs at 1,000 feet per second, which is very realistic in my book for the pressures and barrel length DYI is planning on using, you'd get just under 15 ft/lbs of muzzle energy per BB - this means that coupled to a cloud's awesome rate of fire, you'd get the performance of a 22 rimfire automatic at close range in terms of weight of fire :shock: :D

(hint hint DYI ;) )


damn i wish i had access to helium then i could make one :cry:
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Unread postAuthor: DYI » Sun Jan 06, 2008 9:47 am

As I said, the pressure washer will be detachable from the body. And I won't be building a strafer from it until Noname makes my vortex block, which I ordered in September. (hint hint Noname)

A tungsten carbide BB strafer would be awesome, but like Carlman said, the $150/second shooting cost would make it rather impractical. Steel would be a better choice.

Unfortunately, with my current barrel, a strafer, or any breech loading mech for that matter, is impossible, because the comp fitting squeezes the tube too much for the ammo to fit through (which was a deliberate feature of the design, to allow easy muzzle loading with no wadding, and to prevent the BB from sliding into the valve).

I will likely buy another 3' of the .257" ID tube when I order the ammo for the BB gun, so a strafer is a definite possibility.
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Unread postAuthor: Carlman » Sun Jan 06, 2008 10:12 am

I look forward to it :D
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Unread postAuthor: Acdcmonkey1991 » Sun Jan 06, 2008 10:15 am

This whole thing has got to be the sweetest cannon ever, but I have one question, why are your bb's $15 for 5? is the ammo .25 ball bearings, or airsoft bbs?
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Unread postAuthor: DYI » Sun Jan 06, 2008 10:18 am

There are two different kinds of ammo I plan on using in this project:
.25" Tungsten carbide ball bearings, $15 for 5
.25" Steel ball bearing, $20 for about 500
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Unread postAuthor: Carlman » Sun Jan 06, 2008 10:33 am

can u imagine if you lost one of of your carbide ones, youd be pissed lol

EDIT: o yea new rank!! :D
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Unread postAuthor: DYI » Sat Jan 19, 2008 7:13 pm

Update:

I pressure tested the pressure washer handle with nitrogen, and was extremely disappointed; it had developed an easily detectable leak through its valve at only 500 psi. With 2.4kpsi helium, the leak would be massive, and unacceptable to the design. The valve internals are encased in what appears to be a forged brass outer body, and are completely inacessible for modification.

The steel bar stock I obtained is too hard to be properly machined with any bit. The quote I obtained from a machine shop for building the valve was, well... :cry:

Unless someone that can machine to .001" tolerances would be willing to do a discounted job for me on the valve work, this project is regrettably postponed indefinitely, in favor of further modifications to the SCTBDC which definitely will work. I would like to emphasize that while the project has not been relegated to the scrap heap, I won't actively be working on it until I can find a reasonable solution for the machining work.

Sorry guys :(
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