How-to: rifle metal barrels

[Demon]

I have a question :

So that the bullet spins in the barrel, dont you need it to get the bullet stuck in the rifling so that it can act as an rail? When the bullet goes out, it should be rifled on the sides, no?



Then why paintball rifled barrels exist? Or even potato ones(sold by spudtech), i doubt the potato "fins" would survive long to the rotation, no?

Does anybody know?

[ramses]

the potato ones actually do work, because the rifling rate is so low. As to the PB rifled barrels, this is most likely marketing BS, depending on how it's done. It has been shown that things like the flatline do impart spin, but I double grooves will grip a paintball without breaking it.

[Hubb]

Hammerhead barrels are some of the best, most accurate barrels on the market for paintball. They are rifled. People claim that the liquid inside the paintball actually works against the spinning, but I don't recall seeing any definitive testing on it.

As far as potatoes, Burnt Latke cleared that up. He had tremendous accuracy gains by using a rifled potato barrel. I would think that the potato slug would actually be easier to go into the rifled grooves than just about anything else.

[al-xg]

As far as paintball is concerned the biggest difference in accuracy is mostly due to the quality and type of paint used. I have found a homemade barrel made from aluminium tube to me more accurate than some stock barrels.
Rifling in a paintball barrel would work best with that same good paint.
When I get back to my workshop I will do a test between two aluminium tubes rifled and smooth.


But for spudguns it does make a big difference, the potato slugs I fired hit the target head on even at high pressure and no porting.

[mikespahn]

this is basically a simplified version of one of the most common ways gun barrels are rifled. button rifling. other common methods include broaching and hammer forging (normally only used in large production volume). i have also heard of doing it via electrochemical machining. none of those really apply to spudguns. i mean i suppose you could, but they wouldn't be very practical.

good instructional.

[monsteroftheemptysun]

the rifling on potato cannons works because the fins on the projectile have, for all intents and purposes, zero effect on the actual spinning of the bullet.
the rifling gives the bullet a spinning momentum, so it keeps spinning because of momentum physics, not aerodynamics. a good example of this force is how a top keeps spinning after you take your fingers off it.