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Discontinuous Rifling

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Discontinuous Rifling

Unread postAuthor: auxiliary » Thu Jul 02, 2015 7:10 pm

Hi spudders!

I've got a question for you! I've got my new airgun I built here: http://www.spudfiles.com/pneumatic-cannon-database/topic26216.html and I have a 10.5" .45 cal rifled barrel inside it. I want to get some more length out of it to better utilize the air for each shot to increase velocity. So what I did is ordered a 12" seamless stainless steel pipe with the same 5/8" OD and an ID of 0.459". I want to use this to extend my current barrel.

So, question time! What should I put first, the smoothbore or the rifled barrel? I will sleeve the two barrels inline with a SCH 40 1/2" nominal aluminum pipe with ID of 0.622" and sand it a bit. I plan to use a variety of ammo including .44 cal wax dipped lead bullets, .45 cal lead bullets, taped 3/8" steel rod slugs, darts and more...
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Re: Discontinuous Rifling

Unread postAuthor: cammyd32 » Fri Jul 03, 2015 6:01 pm

I am no ballistics expert, but I somehow have a feeling that having two barrels attached halfway in either combination would probably negate any accuracy gains from the rifling,

However if you do choose to do this, I would put the rifled section first, this way the pellet doesn't hit the rifled section at near maximum velocity, which could cause a lot of damage on the projectile, and the beginning of the rifled barrel over time.
Also worth considering that maximum acceleration is usually during the first half of the barrel, and therefore most suited to the higher frictional forces, and extra energy required for imparting the spin, found in a rifled section.
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Re: Discontinuous Rifling

Unread postAuthor: Solar » Sat Jul 18, 2015 6:50 am


Smooth bore first to allow the projectile to accelerate with less friction then engage the rifling. Otherwise the rifling effect will lose rotation due to friction if it continues down a barrel post rifling.
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