Quote:
Originally Posted by cottontop
1 in 10
cottontop
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Using a modified Greenhill formula and Hodgdon's reloading data for muzzle velocity, your ideal bullet length for a 1:10 is:
Muzzle ..... Bullet
Velocity ... Length
2300 ........ 1.59
2400 ........ 1.63
2500 ........ 1.66
2600 ........ 1.69
2700 ........ 1.73
2800 ........ 1.76
Twist = 3.5 x MV^0.5 x Dia^2 / BL
MV is muzzle velocity
BL is bullet length
Dia is bullet diameter
The original Greenhill formula did not have a term for velocity this includes
velocity and I have found to be a good indicator.
You can over spin a bullet and loose accuracy and in rare cases actually have
a bullet pulled apart by the forces. Seen it done with a very short and light
bullet in a hot 5.56 Nato round.