You stay in that range, and you'll be alright. Sierra Game Kings are great hunting projectiles, no matter what you'll hunt. That weight range of the 165 SGK will keep it pretty close to what you're doing now with the 168 Match Kings, dope won't be far off, for distances - unless you're going LONG. If you're staying under 600 yards, it won't much matter, between the two projectiles.
Another one to consider, based on your intended purpose, is a Hornady Precision Hunter load with their own ELD-X projectiles. The only Precision Hunter load they offer for .308 Win is the 178 ELD-X, and I'm not sure how that would do in the M1A. That projectile is the best one they've got for .308 Win, amongst all their projectiles, even the ELD-M. I switched my .308 Win handloads over to that projectile about 3 years ago, and I'm glad I did. Works great for precision, distance, and hunting.