Thread: Fussy 243.

Originally Posted by TARGEX

Out of interest for anyone reading all this it is not bullet weight that decides required twist rate but bullet length!
if there was a heavy enough core material available I could make a 200gr bullet that would stabilise in a 6mm 10" twist barrel as long as the finished bullet length was short enough.
This is also the reason that plastic tip bullets in various calibers wont stabilise as the bullet LENGTH can exceed the barrel twist even though the bullet weight is supposed to work.
Hope this makes sense.
Cheers.

In the 1850s this was figured out by a bloke called green hill who came up with a formula to calculate the twist rate needed for any bullet length or alternately the longest bullet that will work with a given twist. It completely ignores weight . It also takes into account the projectile speed as as a bullet slows it's rotational speed slows and gyroscopic stability decreases. Which explains the occasional I'm on target at 100 yds but can't hit the target at 200. I know I've been there.

Originally Posted by Marty Henry

In the 1850s this was figured out by a bloke called green hill who came up with a formula to calculate the twist rate needed for any bullet length or alternately the longest bullet that will work with a given twist. It completely ignores weight . It also takes into account the projectile speed as as a bullet slows it's rotational speed slows and gyroscopic stability decreases. Which explains the occasional I'm on target at 100 yds but can't hit the target at 200. I know I've been there.

Actually the opposite is true, rpm degrades much less quickly than velocity....so bullets on the verge of stability wobble there way out untill velocity has dropped enough that the rpm will hold them stable.