Rotational effect on bullet expansion??????

[308sako]

This is a question which I seem to be unable to answer or have answered to my satisfaction. I must be one hard case... ??? Does the rotational speed of a bullet have a major influence on a bullets expansion in consistant media. This would apply to any caliber and weight projectile of an expanding nature. Meaning a 165 grain .308 diameter bullet fired at a muzzle velocity of 2700 feet per second (in a 1 in 12" twist barrel) has a rotational factor in RPM's of 162,000. The same bullet when fired from a 1 in 8" twist barrel would have a factor of 243,000 RPM assuming the same muzzle velocity. I should also note that I do not subscribe to the over stablized bullet theory for realistic/ethical hunting ranges. Thanks for the input.

 

[longwinters]

:lol: :lol: Hey 308,

I think you have too much time on your hands :lol: :lol:

I hope we have some real Physics oriented people on here but I know I am not one of them.

Long

 

[NOSLER]

308 let me take a crack at this one.


For everyones benefit, a bullet in a 1-12" twist barrel will rotate once every 12", 1-10" every 10" and so on whether it is 10 yards from the barrel or 300 yards.

The faster the bullet goes the easier it is to stabilize, it will not however spin any faster than 1-10" or 1-12", it will however have more rotations per second. So if you turn up the RPM's the bullet will not spin more than the twist rate.

But if the RPM is cranked up, your speed will be cranked up as well out of the same twist barrel.

Now there is a background.

The basic underlying factor in bullet expansion is velocity at impact. If that means you are shooting a 1-12" or a 1-8", the major influence will continue to be velolcity.

Hope that helps.

 

[308sako]

Thanks for the clear answer that velocity at impact is the key factor in expansion. I didn't mean to imply that there was some "hidden" significant Physic's Law which we all had been avoiding, but rather that the apparent "great" difference in rotational speeds would have some more major effect on the mushrooming characteristic, and therefore the wound channel. Yup... I must have too much time on my hands. Thank you both.
dd