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semi auto questions

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: jackssmirkingrevenge » Thu Dec 20, 2007 2:10 pm

ALIHISGREAT wrote:aww they are catergorised by model... so i can't just look at all the barrels in one section, do you know of a .22 air rifle with a long barrel?


There's the Career if you have 75 quid to spare, or you can get a Crosman 2260 barrel for 1/3 of that price.

Air rifle barrels are usually short by spudgun standards, what you can do is have a long smoothbore barrel then graft the airgun barrel to the end of it, this way you get high acceleration and the benefits of rifling.
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Unread postAuthor: dyldo » Thu Dec 20, 2007 3:28 pm

Air rifle barrels are usually short by spudgun standards, what you can do is have a long smoothbore barrel then graft the airgun barrel to the end of it, this way you get high acceleration and the benefits of rifling.


that sounds like a plan since iv already gone through the time and effort cutting the grove on the plane barrel. do u think theyd ship to Australia? customs?
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Unread postAuthor: qbnbountyhunter » Thu Dec 20, 2007 3:41 pm

Where did your get that small sprinkler valve? Can you get it in America?
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Unread postAuthor: ALIHISGREAT » Thu Dec 20, 2007 3:55 pm

how would you suggest graphting the two barrels JSR and would sticking two rifled barrels together work as long as they are the same?
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Unread postAuthor: Ragnarok » Thu Dec 20, 2007 3:59 pm

ALIHISGREAT wrote:...would sticking two rifled barrels together work as long as they are the same?

That's a tough question that depends on whether the rifling/barrels is/are lined up, and whether the rifling had an equal twist rate at both ends of the barrel. Quite a few barrels don't.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: jackssmirkingrevenge » Fri Dec 21, 2007 12:09 am

dyldo wrote:that sounds like a plan since iv already gone through the time and effort cutting the grove on the plane barrel. do u think theyd ship to Australia? customs?


I'm sure a rifled barrel would attract attention at customs, particularly in a place with such strict gun control.

how would you suggest graphting the two barrels JSR


what a silly question, EPOXY of course :D

That's a tough question that depends on whether the rifling/barrels is/are lined up, and whether the rifling had an equal twist rate at both ends of the barrel. Quite a few barrels don't.


Different twist rates aren't that much of a problem, for example in this Elswick Ordnance Company 6 inch Mk. IX gun, the twist rate changes 5 times along the barrel length - though of course, the rates would have to match at the point where the barrels meet, otherwise it could tear your pellet to shreds.

I would suggest grafting a barrel to a smoothbore tube though, it's a cheaper solution and will be just as effective. Shotguns for example can be fitted with rifled choke tubes to fire slugs more accurately, this only provides rifling for the last few inches of barrel.
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Unread postAuthor: ALIHISGREAT » Fri Dec 21, 2007 4:48 am

the problem is finding a perfect smoothbore tube and then alligning it perfectly although i suppose the tube wouldn't have to be very long and for easy connecting (to valves etc.) the extended barrel could be put in an outer barrel of 15mm copper like on my 6mm 'sniper'
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Unread postAuthor: jackssmirkingrevenge » Fri Dec 21, 2007 6:00 am

ALIHISGREAT wrote:the problem is finding a perfect smoothbore tube and then alligning it perfectly


all you need is a wooden dowel of the right diameter et voila, problem solved - that's how I align my silencers etc.
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Unread postAuthor: ALIHISGREAT » Fri Dec 21, 2007 6:12 am

pure genius, i would have thought of that given more time... honest
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Unread postAuthor: dyldo » Sat Dec 22, 2007 7:10 pm

Where did your get that small sprinkler valve? Can you get it in America?

i got it from a Reece irrigation store not sure if u have the stores in America but an irrigation store would carry them i s pose.

I'm sure a rifled barrel would attract attention at customs, particularly in a place with such strict gun control.

Yer true i need to try something though im finding my pellets/ projectiles are tumbling in the air.
will making them longer or shorter help?
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Unread postAuthor: jackssmirkingrevenge » Sun Dec 23, 2007 7:48 am

dyldo wrote:Yer true i need to try something though im finding my pellets/ projectiles are tumbling in the air.
will making them longer or shorter help?


A medium weight airgun pellet will not tumble, even if fired from a smoothbore barrel, because of it's shuttlecock or "diablo" shape - 0.22 pellets can be made to fit like so, and 0.25 pellets should fit comfortably too if you swage them down a little.

Are you making your own projectiles or using something commercially available?

Where did your get that small sprinkler valve?


A good (and usually free) source of smaller solenoid valves is old washing machines and dishwashers, very suitable for BB barrels.
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Unread postAuthor: dyldo » Sun Dec 23, 2007 8:15 pm

Are you making your own projectiles or using something commercially available?

yes im cutting 6mm steel rod which is actually 6.3mm into 15-20mm lengths to use as slugs cheap and readily available. i cant get bbs as yet working on it though
would making them shorter or longer help?

also would drilling holes through the barrel before the end venting the air help. i noticed paint ball guns have them half way down the barrel.
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Unread postAuthor: jackssmirkingrevenge » Mon Dec 24, 2007 6:42 am

what would help is keeping the same length but drilling a 5mm hole down about 75% of the way to act as a tail
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Unread postAuthor: dyldo » Wed Dec 26, 2007 9:24 pm

what would help is keeping the same length but drilling a 5mm hole down about 75% of the way to act as a tail

through the projectile? or the barrel?

the semi-auto mechanism isn't working its not moving forward enough to cover the hole and the spring isn't reseting it so iv giving up for a while:(

i have put this together
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6mm barrel inside 18mm pvc
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Unread postAuthor: jackssmirkingrevenge » Wed Dec 26, 2007 10:07 pm

dyldo wrote:the semi-auto mechanism isn't working its not moving forward enough to cover the hole and the spring isn't reseting it so iv giving up for a while:(


Sorry to hear that - perhaps there is too much friction in the system?

dyldo wrote:through the projectile? or the barrel?


I mean the projectile, as per the attached diagram:
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this way, the hollow rear will act as a "tail" and stabilise the projectile in flight.
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