Stability and Spin Drift

[Canadian bushman]

Will a bullet exhibit more spin drift if it is marginally stable?

 

[Berger.Fan222]

Will a bullet exhibit more spin drift if it is marginally stable?

Not according to equation 6.1 of "Applied Ballistics for Long Range Shooting" which predicts more stable bullets to have greater spin drift.

 

[Canadian bushman]

Not according to equation 6.1 of "Applied Ballistics for Long Range Shooting" which predicts more stable bullets to have greater spin drift.

I had to pull out the book to look up the referenced equation.

Drift = 1.25(Sg + 1.2)tof^1.83

Berger.fan is correct if we assume the equation holds.

Thank you for that Berger.fan

 

[dcali]

Spin drift is proportional to, well, spin. Faster twist = more drift.

If you want to be technically precise about it, it's not directly related to stability. But Bryan's equation is a good rule of thumb approximation - a curve fit to empirical data. The alternative requires hard to get information on bullet aerodynamics, so that's a pretty good way to go about it.

 

[Canadian bushman]

Is it possible to not experience spin drift with a well stabalized bullet?

 

[dcali]

Is it possible to not experience spin drift with a well stabalized bullet?

No.

 

[Berger.Fan222]

Is it possible to not experience spin drift with a well stabalized bullet?

You'd need a fin stabilized or other drag stabilized projectile that didn't spin - maybe something from a smooth bore analogous to a shotgun slug or some larger caliber rounds. Not really rifle bullets.

 

[dcali]

Technically, a round ball wouldn’t drift.

 

[DocUSMCRetired]

If it is gyroscopically stabilized. It is going to drift. You can minimize the drift by getting as close to an SG of 1.0 as possible. But you lose about 3% +/- BC for every 0.1 below an SG of 1.5. Below 1.0% you run a good chance of tumbling them. The higher the SG the more drift.