Stability Programs ?

[Wayne S]

Is there one of these programs that is more "real life" accurate that the others ??http://castboolits.gunloads.com/showthread.php?t=102895&page=4
plus the Jim Miller and a few others
???????????

[Pat I.]

I've always used regular old Greenhill for a lot of cast bullet projects and it hasn't let me down yet. I always figured a lot over stabilized was a heck of a lot better than a little under stabilized.

[Wayne S]

I've always used regular old Greenhill for a lot of cast bullet projects and it hasn't let me down yet. I always figured a lot over stabilized was a heck of a lot better than a little under stabilized.
Pat, neither are very good, under stabilized and the bullet will wobble causing key holeing, over stabilized and minor defects become MAJOR defects, thats why the "stool shooters" strive for their bullets being very close to being under stabilized, thus the 1-14 twists in 22 & 6 MM and 1-16-1-18 twists in 30 Cal. with 110 gn bullets.
looks like it's time to test these 200 gn. bullets in a 1-10 twist , after making some SWAG's on 1300 FPS load data
Ain't it always something

[turbo1889]

This is the formula I use:

T = 3.5 * V^0.5 * D^2 / L

where:

T = Twist in terms of inches per one complete twist
V = Expected muzzle velocity of load in feet per second
D = Boolit diameter in inches (use decimal fractional)
L = Boolit length in inches



That is the Greenhill formula with the velocity correctional factor. It does not include the correctional factor for modern jacketed boolits (original Greenhill was cast or swaged lead) or the correctional factor for the more pointy modern spitzer type boolits (original Greenhill assumes rather blunt nose shapes). I find it works very well for my needs with cast boolit loads and I often solve for boolit length and/or muzzle velocity since twist is usually a known factor that isn’t easily varied to tune a load. It is much easier to adjust boolit length (choice of boolit used) and muzzle velocity to tune the load and find a combination that works with the gun one already has with the twist that is already built into the barrel.

[Wayne S]

you mean like this http://http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

[Wayne S]

This is the formula I use:

T = 3.5 * V^0.5 * D^2 / L

where:

T = Twist in terms of inches per one complete twist
V = Expected muzzle velocity of load in feet per second
D = Boolit diameter in inches (use decimal fractional)
L = Boolit length in inches



That is the Greenhill formula with the velocity correctional factor. It does not include the correctional factor for modern jacketed boolits (original Greenhill was cast or swaged lead) or the correctional factor for the more pointy modern spitzer type boolits (original Greenhill assumes rather blunt nose shapes). I find it works very well for my needs with cast boolit loads and I often solve for boolit length and/or muzzle velocity since twist is usually a known factor that isn’t easily varied to tune a load. It is much easier to adjust boolit length (choice of boolit used) and muzzle velocity to tune the load and find a combination that works with the gun one already has with the twist that is already built into the barrel.
Ok , my choices in twist are; 1-8, 1-10, & 1-11, bullets are 30 Cal. 205 gn, 1.2",1.27", case capasity will limit V to 1450 FPS

[turbo1889]

1.2” length boolit at maximum velocity:

T = 3.5 * V^0.5 * D^2 / L
T = 3.5 * (1,450)^0.5 * (0.309)^2 / (1.2)
T = 10.6


1.27” length boolit at slightly reduced velocity:

T = 3.5 * V^0.5 * D^2 / L
T = 3.5 * (1,300)^0.5 * (0.309)^2 / (1.27)
T = 9.5


If we assume the formula that I use is the correct formula to use it looks like the 1-10 twist would be your best choice for the figures you gave.

[HARRYMPOPE]

i just shot this 225g 1.2" FN plain base 30 caliber in a 7.62 x 54 91-30 Russian(1-10 twist) .It did not group spectacularly,but was stable.High shot was shot #1 others dropped down.
The load was 12.0 of TrailBoss and win lg pistol prmer.

22E.S.
S.D. 6.5
Vel 1174 avg.

HMP