This question goes out to folks who have owned and shot both types of rifles. I have a project coming up where I need a semi-auto rifle with low dispersion (<.75 MOA for a 5-shot group at 100 yds). I need the ballistics of the 7.62 NATO M118-LR cartridge, and a max range of at least 1,000 yds at sea level. I have multiple AR-15 rifles, but no AR-10/SR25/GII/... rifles. I started to look at rifle prices and asked myself if I could get the same drop and wind drift in an AR-15 platform. I was a bit surprised to see that the 6.5 Grendel with a 123 gr Scenar has nearly the same ballistics (not including bullet energy) as the 7.62 NATO 175 gr M118-LR round. It's really wind drift that I'm trying to match, not bullet drop. I could save more than a few bucks by buying or building a 6.5 Grendel upper for this project instead of buying a new 7.62 NATO rifle. My question is, am I missing something here? Is there a good reason, either for ballistics or rifle function, reliability, accuracy, etc., to use an AR-10/SR25/GII/... rifle instead of a. 6.5 Grendel? Again bullet energy is not an issue - I am essentially punching paper in this project.