Re: [Phys-l] Final velocity of bullets

["B. Esser" <besser@marian.creighton.edu>]

On Tue, 23 Jan 2007, Quist, Oren wrote:

> Of course a rifle bullet is spinning as well as translating.  For the
> sake of argument, suppose the bullet spins two revolutions as it moves
> through a 75 cm long barrel.  (these numbers are somewhat arbitrary, but
> reasonably close to actual -- please replace with better numbers if you
> have them).
>
> Is the bullet still spinning when it reaches its maximum height?

It has been a few years since I participated in high power rifle matches. 
Spin rates for these target rifles varied between 100,000 and 300,000 rpm 
as measured at the muzzle. While there were various calculations for 
minimum spin rates to establish stability, most competitors used a more 
empirical method.
In my experience I never saw a tumbling bullet even at 1,000 yard targets. 
The holes in the target were circular. An occasional bounced bullet would 
leave an interesting non circular hole. Of course launch angle was less than 5
degrees and time of flight was less than a second.
Some real bullet data using my chronograph:
30-06 (bullet diameter of .308 inches), bullet weight 150 grains, muzzle 
velocity 2932 fps, velocity at 200 yards was 2,318 fps. This was the 
average of 25 shots. There was no wind, temp at 76 farenheit. While I did 
not measure the actual spin rate for these bullets (Hornady) other 
measurements with identical barrels (twist rate/length) measured muzzle 
spin at 158,000 rpm.


--
Bruce Esser
Physics Teacher
Marian High School
http://marian.creighton.edu/~besser