I have a Ruger precision rifle in 6.5 Creedmor. I recently sent it into Ruger to have some repairs done, and of course removed my scope before shipping. The rifle was precviously zeroed when I first got my Vortex Diamondback Tactical Scope which is 4x16x44. I will be re-zeroing and boresighting it when I put the scope back on. I was wondering...should I set the scope back to factory zero, or can I just adjust and zero from its current zero that I established when I first mounted my scope and zeroed 2 years ago? Thanks!