By the way, your ammo picks sound pretty good to me. The light AR rounds are usually over stabilized with fast spin rate, but would do OK out to 100-150 yards. My Ruger Ranch Rifle likes 75 gr the best for longer ranges.
Modern bullets cannot be over-stabilized for the most part (meaning spun to the point of losing accuracy/becoming gyroscopically unstable). True, varmint/thin jacketed or plated bullets can be made to come apart with too great a twist rate, but anything else- not so much.
Accuracy degradation in the old days from poorly made non-uniform bullets indeed caused inaccuracy, but run a modern match 52-90 grain BTHP from any manufacturer down to a 1/6.5 twist and they drill accurate and precise holes.