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New homemade gun and stock (before staining), just finished!

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: DaxSF » Fri Jan 25, 2013 3:39 am

jackssmirkingrevenge wrote:
DaxSF wrote:Regarding the pressure, I am now buying a small compressor which will go 200~250 PSI


If it's one of these, save your money.

[img]http://i00.i.aliimg.com/photo/v0/442904640/12_volt_car_air_compressor_mini_air.jpg
[/img]

Get one of these instead: http://www.ebay.com/itm/Bicycle-Bike-Al ... 416746073d

Will give you a bit of exercise too ;)

I really don't have any use for more than that I think. The gun is already 400 FPS+ (estimated via coke can chrono test).


Boooooo! MOAR POWAH!!!!!

:D


Lol, I go to the gym :( I don't need to exercise! Just kidding, adding some plates to the bench won't hurt anyone ;)

Back on topic: LOL this is the exact same compressor I was going to buy! I actually wanted a compressor so there is an automatic charge, I hate manual pumping. The difference is only 10 PSI for the manual pump, and these kind of pumps cost well over $50 where I live, while the compressor costs more like $20..
Also I think the 6mm barrel will result in some major FPS incline because of the "snugger" BB fit (right now it just falls out of the barrel if I aim too low).
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 25, 2013 3:46 am

DaxSF wrote:The difference is only 10 PSI for the manual pump, and these kind of pumps cost well over $50, while the compressor costs more like $20...


On paper, you'd be right. But the reality is that these compressors are about as useful as a chocolate teapot, and will overheat and die long before they reach 250 psi.

A manual pump can also be used anywhere.

Also I think the 6mm barrel will result in some major FPS incline because of the "snugger" BB fit (right now it just falls out of the barrel if I aim too low).


Barrel tightness is *very* important. I did a test a very long time ago:

[quote=2005 me"]It's fairly obvious that the closer the barrel diameter is to the projectile diameter, the less air is wasted and therefore, more power. I decided to set up a simple experiment to see just how much of a difference it makes.

The basic setup was two 15 inch lengths of barrel tubing, one was aluminium with an I/D of 5mm, while the other was a straighted piece of coiled copper tubing with an I/D of 4.5mm. The barrels were hooked up to a blowgun attached to a compressor and used to fire lead BBs - with a nominal diameter of 4.5mm - at 100 psi through a chrony.

Over a 5 shot string, the 5mm I/D barrel averaged 242 feet per second, whilst the 4.5mm I/D barrel averaged 279 feet per second.[/quote]

A projectile with 10% less diameter than the barrel resulted in 25% less energy, that is very significant.
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Unread postAuthor: DaxSF » Fri Jan 25, 2013 4:05 am

MAN I love eBay! Just ordered some 6mm brass tubes since the smallest diameter I could find in this entire country was this 8mm and that was only because I found it from a scrap lamp post (go figure..) :roll:
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Unread postAuthor: wyz2285 » Fri Jan 25, 2013 6:36 pm

Incorporate a onboard shock pump would be a good option, but your chamber maybe too big to take advantage of the high pressure it offers.
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: iloveairguns » Sat Jan 26, 2013 9:47 am

It seems to be a coax airgun... Plz take a pic from the front plz plz plz :razz:
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Last edited by iloveairguns on Sat Jan 26, 2013 9:57 am, edited 1 time in total.
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Unread postAuthor: DaxSF » Sat Jan 26, 2013 9:54 am

iloveairguns wrote:Is it a coaxial airgun? just asking...


Yes it is.
After finishing this gun completely (probably next week, when all the parts arrive from eBay), I plan on making a new bullpup, semi-auto with a QEV I bought.

EDIT: Didn't see the edited post. I will take proper pictures tomorrow probably.. If you're interested in taking a look at the gun, PM me.
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Last edited by DaxSF on Sat Jan 26, 2013 10:03 am, edited 1 time in total.

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Unread postAuthor: iloveairguns » Sat Jan 26, 2013 10:01 am

Woah quick reply, well cool if your gonna make it a bullpup and a pic would be nice of the front, and what type of trigger system does it have? Is it the schrader type?
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