I use a Springfield Armory ART IV 3-9x40 scope. It has a stadia rangefinder built in and it's drop compensated for a 308 Win cartridge used in an M1A rifle. No target knob twiddling or calculations are required from 50 to 500 yards. Here's one for sale used at a good price:
Springfield Armory 3x9 A.R.T. IV Rifle Scope 308 *Used | eBay
I use a Gen III SA scope mount with Leupold low steel rings. It's solid, reliable, comfortable eye placement, and doesn't interfere with ejection.
There is also the SA 4-14x56 scope designed for use with the M1A. it has a range calibrated reticle to match the 308 Wn cartridge plus an internal bubble level for anti cant. It's not designed to be a rangefinder, rather to be used with a handheld laser. Again, no knobs to twiddle to use it. I chose the 3-9x40 because it's less weight and more compact.