The rifles normally have a 1 in 12 barrel as such would prefer 50 to 55 grain bullets, I would suggest a 52 grain A-Max from Hornady (#22492) driven with by Hodgdons BL-C(2) powder which I found to be most excellent in my .223.
Quick load suggests that 26 grains will be a light load , producing 3142 fps or 1141 Ft-Lb ME (with 26.5 being just compressed) and that 28 grains would be as hot as you would want to really go with 3415 fps or 1346 ft-lb ME and is a compressed charge from 26.5 grains to 28 grains. Taken on a COAL of 2.26"
MY pet load in my old M77 .223 was 23.5 grains of BL-c(2) dri