It does appear that most here prefer bashing Muleskinner rather than anything meaningful -- so the following is for the minority of you all who're interested in technical matters.
The question was asked so long ago that I don't remember who asked it or even on which board, but here's the answer as provided by Mathcad 8 Professional and the mistakenly maligned classic Greenhill equation.
The question -- what's the best twist for stabilizing the 75-grain Hornady A-Max .224 bullet?
The equations -- minimum (shortest) twist = 150 times the diameter of the bullet, squared, divided by the length of the bullet
-- maximum (longest -- usually optimum) twist = 200 times the diameter of the bullet, squared, divided by the length of the bullet
After much diddling around getting acquainted with the complexities of Mathcad 8, I finally learned how to feed it the right flavors of the math for my old unproductive file on the Greenhill equations. My reward: the minimum and maximum twists for a .224 bullet 1.105 in. long:
minimum 6.811 inches (6.9 or 7 inches)
maximum 9.082 inches (9 inches)
A 7-inch twist (a) overstabilizes the bullet at any velocity and (b) overspins it at top velocities available in the .220 Swift, .22-6mm, and .220 Howell. At best, a 7-inch twist limits the top velocity that doesn't tear the 75-grain .224 A-Max apart just beyond the muzzle.
A 9-inch twist lets the 75-grain .224 A-Max hold together at higher velocities but requires a higher-quality barrel. (The Richards barrel on my .220 Howell, for example, is a very smooth three-groove barrel with a nine-inch twist.)
For lesser-quality barrels -- or barrels of unknown or unproven quality -- an 8-inch or 8�-inch twist is probably the practical maximum.
