The Varmint Grenades are really finicky about twist rate and seating depth.
My Shilen Select Match shoots the .204" VG's very accurately even though the barrel is a 1:12" twist. I have recorded 10 shot groups of .247" - .250" when taking pains with loading. This barrel prefers factory seating depth.
The 6mm VG's really have to be spun in a quick twist barrel. A 1:10 .243 Win. barrel usually won't do it. I had a Shilen Select Match 1:10" done up in 6mm PPC .262" neck because the Sako's 1:14 barrel threw them out sideways, base first, at the target two frames over, etc. The Shilen 1:10" still wouldn't group consistently, throwing fliers every few shots. So I reamed the throat to seat them out further and increase velocity by getting them out enough to add more powder. No go. 1:10" is too slow.
So ordered a .243 WSSM 1:8" barrel and tried that. More speed, more twist, went 1.97 with the Miller Stability Formula. They shoot little bug holes now, seated at factory depth. 3,850 fps should produce massive squirrel displacement.
Same with the .22-250 on a 40X action. I ordered a 1:10 twist Pac-Nor for the 50 grain VG's. It shoots okay, around .5" with an occasional flier. Should have gone 1:9" or even 1:8".
Ordered another Savage barrel from Pac-Nor in .223 Rem. with a 1:9 twist for the 50 grain VG. Oh dear - that's the ticket. It shoots both sides of .5" mostly under if I do my part.
Bottom line, if the lead free bullets from Barnes or Nosler, or the new Hornady's (these have tungsten added to the core metal for weight) shoot lousy the twist is too slow. These new lead free bullets, including the monolithic copper expanding types, will all require faster twists over lead core bullets.