Building an AR-15 is one of the best ways to get a custom rifle and familiarize yourself with the platform.
The XPS2-300 uses the standard mounting system that quickly and easily mounts to any standard 1-inch Weaver or Picatinny rail and will re-zero within 2 MOA if removed and remounted — not perfect, but not bad. This is close enough to get you back on target and make re-zeroing simple ...