Thread: Bullet twist blow Up Numbers

Hi All,
Read an interesting thread on Snipers Hide about bullet blow ups.
The formula used to work out twist rates and rpms was as follows..
Velocity x 720 divided by barrel twist rate. Sum is RPM's which needs to be under 310000rpm so they say.
E.G. 3400fps x 720 = 2,448,000 divided by 8(twist) = 306,000. So for example a 75 grain 22 ELDM at 3400 should be safe with a 1 in 8, but a 1 in 7 at 3400 could be an issue.
Might help some one working out how fast a twist barrel to order if they are thinking of a specific bullet and speed goal.

interesting way to get it...
done this one manytimes before

if we round figures for ease
270 with 1;12 twist...instead of 1: 10 but guess can add 20% to final figure to be accurate

3000fps =3000 times spun per second x 60 seconds per minute 3000x60 =180,000 rpm chuck extra 20% on that 18devided by 5 x6=21.6 chuck zeroes back on
216,000rpm
thats one hell of a lot of spin and centrifical force trying to pull projectile apart....
you fellas with fast twist barrels of 1:8 thats a full 25% faster/more pull
Ive mused on this one before,in theory a faster twist should make same projectile expand more than slower twist barrel....

Sorry but I think they may have missed a bit off that formula.
Bullet caliber/diameter has a big effect as well. ie the larger diameter bullet will experience a much greater centrifugal force than a smaller one.
Ie all things being equal a 223 bullet will withstand a much greater rate of spin than a 45 cal bullet.
Plus then jacket thickness and bonding and core harness etc come into play as well.
Z