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8.1mm ammo?

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8.1mm ammo?

Unread postAuthor: john bunsenburner » Thu Sep 17, 2009 11:05 am

I have found a supplier in Germany for ball bearings but they have a diameter of 8.1mm. I surely won't be able to find a barrel with an 8.1mm ID, but maybe 8.5mm would be doable. If 8.5mm too loose of a fit for an 8.1mm projectile, or would it be alright?
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 17, 2009 11:13 am

I found that for a 4.5mm projectile, a 4.5mm barrel had a 33% power increase over a 5.0mm barrel, so there will be noticable power loss compared to an 8.1mm barrel. Also since the BB will bounce around the barrel there is no guarantee at what angle it will leave the muzzle so don't expect match winning accuracy either.
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Unread postAuthor: john bunsenburner » Thu Sep 17, 2009 11:34 am

Crap...well i might go and use 6mm ammo then...I'll see. Thanks jsr.
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Unread postAuthor: psycix » Thu Sep 17, 2009 12:58 pm

(RC) Hobby stores carry small diameter tubing, and my local store carries sizes like: (ID-OD)
4.1-5
5.1-6
6.1-7 (My bb barrel)
7.1-8
This is to make them able to telescope into each other.
They also carry a tube with 8.1 ID. :)


Dont forget you can always use wadding.
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Unread postAuthor: john bunsenburner » Thu Sep 17, 2009 1:03 pm

Haha, wadding on a semi auto will be difficult...

I asked the supplyer, if the prices are not dramatically different I may just go with 8mm, if not i guess I will start looking for 8.1mm barrels...
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Unread postAuthor: Technician1002 » Thu Sep 17, 2009 1:13 pm

john bunsenburner wrote:Haha, wadding on a semi auto will be difficult...

I asked the supplyer, if the prices are not dramatically different I may just go with 8mm, if not i guess I will start looking for 8.1mm barrels...


Don't overlook that the tubing is maluable. A modification to the principal of a tubing flair or swedge tool, a tool can be made to enlarge the tubing.
I would grind an old 8mm drill bit into the tool, use oil and drive it through.

Make something like this that can be driven all the way through the tubing enlarging it to the new size. This tool is designed to enlarge the end of a pipe so they may be joined without fittings. Mod or make one to enlarge the entire pipe. I've considered making one to make the transition cone for an air ram for supersonic attempts.

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Last edited by Technician1002 on Thu Sep 17, 2009 1:15 pm, edited 1 time in total.
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Unread postAuthor: john bunsenburner » Thu Sep 17, 2009 1:15 pm

Alright what do I get:

5.95mm for 5.50Euro/1000balls
or
7.938mm for 12.90 Euro/1000balls
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Unread postAuthor: POLAND_SPUD » Thu Sep 17, 2009 1:19 pm

you might as well use lead 5.6mm pellets
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Unread postAuthor: john bunsenburner » Thu Sep 17, 2009 2:07 pm

They have a worse fit and are most probably more expensive, also i want to shoot the balls over and over, lead will deform. Also lead is more expensive, and so i think i'll go with the 7.938mm ammo.
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 17, 2009 8:26 pm

john bunsenburner wrote:Alright what do I get:

5.95mm for 5.50Euro/1000balls
or
7.938mm for 12.90 Euro/1000balls


It depends what you want to do with it. For a given valve, chamber size and barrel length, the smaller ones will probably travel faster with a flatter trajectory but the larger ones will have more energy and will probably give a quieter shot.
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Unread postAuthor: john bunsenburner » Fri Sep 18, 2009 10:00 am

I think I will go with the larger ones simply because it is easyer to work in slightly larger diameters, especially on a prototype gun.

Maybe I will make an airsoft version later on.
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