I have definitely seen the effect of twist with varmint bullets, in fact Nosler Varmageddons. When they first introduced them I went on a prairie dog shoot with several rifles, including a "tanger" Ruger 77 .220 Swift with the 55-grain tipped Varmageddon loaded to 3800 fps.
Anybody who's shot a Swift much knows it tends to perform some serious lift and separation on PD's, and this one was no different. But the results still were noticeably less violent than the same bullet at 3100 fps from a Nosler/Noveske AR-15--which had a 1-8 twist. The ranges were the same, from around 50 yards out to 300+, and the .223 definitely and repeatedly did more damage than the Swift.
There was a Cooper for sale at Cabelas a couple years ago, .22-250AI with a 1 in 8 twist. That would have been real interesting, but I just could not swing it at the time
