ACOGs run well over $1,000. An Aimpoint or Eotech is less than half that. Put the difference into training and range time.
Not even gonna get into the 1/7 to 1/9 debate. And as for actually finding case lots of 77 grain OTM ammo, good luck. Last I checked it was $1.00 a round or so.
L
I have a Burris AR-332 3X prism sight that is about a third of that. I've used it on both an AR-10 and AR-15. It's quite rugged and easily handles the recoil on the 7.62. It's very compact, and Burris makes a quick detach mount that enables me to remove and replace the sight repeatedly without loss of zero. I would highly recommend looking for a solid optic take a look at it.