This is a for what it is worth.
Twist formula
Just copy this and paste it into a spread sheet (block C1 is a good option).
=(30*+C5)/((+C7/+C4)^2*+C4^3*+C6/+C4*(1+(+C6/+C4)^2))*(+C8/2800)^(1/3)*((+C9+460)/(59+460)*29.92/+C10)
Then copy and paste this (to make it simple, put the 'Where' in block E2).
Where:
Sg - is the stability coefficient and should not be less than 1.4, but more is ok
C4 - Caliber in inches (.223 for both .222 and .223)
C5 - Bullet Weight in grains
C6 - Bullet Length in inches
C7 - Barrel Twist in inches per turn
C8 - Muzzle Velocity in fps
C9 - Temperature in degrees F (59F normally used)
C10 - Pressure in inches of mercury (29.92 normally used)
This will put the variables in the 'C' column from row 4 to 10. The numbers will have to be typed in to the 'C' column. The location that you put the formula will display the final calculation value.
It is not that hard.
Also, barrels can't read, so most will do what they want, no matter what the spread sheet says. They all are a little different but this does give us something to judge with.