The revolutions per minute exhibited by a PPCBoo, as it exits the barrel, can have a direct effect upon how difficult it is to get it to shoot accurately, even if the twist rate matches the projectile length, pursuant to the Greenhill Formula. That is one of the things that makes the 6.5x55 Swede such a challenge . . . its 1:7" twist rate, combined with its fairly high MV, make for very high RPM values. In my experience, any RPM over around 150,000 is going to give you a challenge both in the torque-up department and in the bullet-flight department (accuracy). Below that rate, things are usually easier.
Here is an easy way to determine your load's RPM, given the barrel's twist rate (in inches per turn) and the PPCBoo's MV (in fps). All you have to remember is the number 720. Multiply 720 by your MV and divide by your twist rate (# of inches per turn) and you get rpm.
Example for 1:7" twist and 2300 fps for a 6.5x55 load:
720 x 2300 / 7 = 236,571 rpm
Now THAT is REEEALLY a root'n-toot'n turn rate! No WONDER that baby is to tricky to load for with anything but JBoos!
Example for 1:12 twist and 2400 fps for a 308W load:
720 x 2400 / 12 = 144,000 fps
That is not goofing around, on the turn rate, but it is manageable, even though the MV was higher than in the 6.5x55 example.
Regards, Zeek