Lots of possibilities here.
Tactical scope with Mil-dot reticle. ($100-$2k)
Long-range Tactical/Varmint scope with target turrets. Tasco, Bushnell (100$) Wal-Mart special to high dollar Schmidt & Bender or Leupold Mk IV ($2-3k).
ACOG - I think they are 700$.
EOTech, Burris, or Bushnell holographic. 200-500$
I think it is called dual-witness, but you have the B.U.I.S. and a holographic scope. So if holographic batteries die, you have the B.U.I.S.
- good site with good prices. They have a bargain bin of used, returned and blemished optics.
Quick release rings are pretty slick. Several manufs. Can also get rings with Picatinny rail so you can put laser/flashlight on there as well. Pretty handy when varmint hunting or invading rogue countries. rofl.
Optics Planet is pretty good as well.