Well, If you want "options" in your VARMINT weight bullets, stay off of the fast twists.
As has been touched on, Centrifugal force is what destroys bullets, NOT velocity.
If you want to shoot on the "cheap" with light jacketed bullets, they do not tolerate high RPM's before destruction. Here is the formula for RPM: MV * 720 / twist = RPM
I won't pretend to say that this translates to other diameters, but here is what I found with 22-cal bullets after calling the manuf's.
http://www.shootersforum.com/ballist...pm-limits.html
Remember that if the maker won't tell you, or say "You can't spin them apart"; to hang-up the phone, they have no clue what you are talking about...
Speer's monkey's only answer in FPS, so you have to specifically ask them the twist tested, then do the math with the formula. Nosler claims(specifically asked their head ballistician) that ALL of their bullets(22-cal) survive 4400fps with a 6-twist.... Bullets that can survive 528,000 RPM, will not open with any somewhat lower velocity; it's physics. So given my experience with their BT's, I would say they are around Hornady V-max's strength.