04 May 2009, 22:56
drewhenrytntVelocity to stabilize 400gr?
My 1885 has 1:25 or 1:26 twist. How fast will I need to push a 400gr bullet to stabilize? I know the velocity is not achieveable in the short 10" barrel of my Freedom model 83, but the 28" 1885 may be the ticket. What say ye?
Andy B
07 May 2009, 01:07
El DeguelloVelocity plays a role in stability, but a small part. Length of the bullet is the determining factor. Twist required (in calibers) = 150 divided by length of the bullet in calibers...Greenhill formula.
07 May 2009, 02:42
drewhenrytntI am somewhat familiar with the formula. However, it should be noted that many rifles that achieve "high velocity" have slow twist rates and manage to stabilize bullets that would not otherwise. Case in point, I have seen several factory rifles with twists of 1:14 and 1:12 in 30 caliber that through super velocity will stabilize 180 and 200 grain projectiles.
Will I have enough case capacity for a slower than normal for cartridge powder, I don't know. Gotta start somewhere.
Andy
09 May 2009, 01:15
El Deguelloquote:
Originally posted by drewhenrytnt:
I am somewhat familiar with the formula. However, it should be noted that many rifles that achieve "high velocity" have slow twist rates and manage to stabilize bullets that would not otherwise. Case in point, I have seen several factory rifles with twists of 1:14 and 1:12 in 30 caliber that through super velocity will stabilize 180 and 200 grain projectiles.
Will I have enough case capacity for a slower than normal for cartridge powder, I don't know. Gotta start somewhere.
Andy
The 308 Win. started out with 1/12" twist, and there were factory 200-grain loads for it originally; 150, 180, and 200-grain.
I have used both 200-grain spitzers and 220-grain RN's in 1/12" 308 Wins, and all stabilized well. These loads were slow, 2300 for the 220 grainers. OTOH, 1/14" might be a bit slow for these bullets.....