[JD0x0]

Depends on bullet length (weight)

Increased barrel length tends to increase velocity. A bullet moving faster through the barrel will be spinning faster, so theoretically you could have a slower twist in the rifle and achieve the same spin rate. Tighter twists tend to cause more friction but I'm sure it's fairly negligible.


You wont "need" a different twist for a longer barrel. It's possible to need a faster twist for a shorter barrel if the bullet isn't pushed fasted enough, it may not be spun fast enough and therefore can be unstable.

For the most part, most pistol and revolver cartridges can share twist rates between the pistols and rifles. Generally the pistol twist rate is fast enough, so if it's stabile in the pistol it will be stabile in a rifle, and the rifle wont "over spin" the bullets.

One thing I should clear up, is that a longer barrel wont stabilize a bullet better simply because it's longer. I've had people claim that the bullet doesn't "catch" the rifling right away, so a short barrel may not stabilize the bullet. That is simply not true. If your bullets aren't "catching" the rifling right away your bullets are undersized or your bore is oversized, and it likely wont catch any better down the barrel. You get more stability with a longer barrel because the bullets generally exit faster. If a bullet is moving through a given twist rate, the faster it moves through the rifling, the faster it spins.
If two identical bullets leave two different barrels, one 3'' and one 28'' with equal twist rates, and the bullets leave the barrel at the same velocity, they both should have equal spin rates, and therefore the same stability.