Your .222 Rem cases will perfectly center in the chamber when fired regardless of how much their shoulder's set back from full length sizing them. The firing pin's impact drives the case shoulder hard and well centered into the chamber shoulder a split second before the primer fires. As long as the case neck's well centered on the case shoulder and the bullet runout's no more than 2 thousandths, excellent accuracy is at hand. But I'd not set 'em back more than 2 thousandths for long case life.
If the barrel's a standard factory sporter one, you may get better accuracy with flat based bullets. Sierra Bullets noticed this years ago testing their boattail and flat base bullets in all sorts of rifle barrels. In best quality match barrels, the boattailed ones shot more accurate. But shoot at least 20 shots per test group to be sure.
Sierra Bullet's ogive curve has typically shot best with contact with the lands when chambered. In contrast, many of Berger's bullets' different shaped ogives need a few to several thousandths jump to the rifling to shoot best.
US Navy Distinguished Marksman Badge 153
Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master