I have never owned the model that you're speaking of....but I did have a Rem. Milspec 5R with a 1:11.25" twist barrel. As you found with your other rifle...my 5R did well with better quality ammo from 165 gr. to 175 gr. Federal Gold Match ammo with 175 gr. SMK bullets shot the best of any factory ammo...right @ 1/2" for 5 shot groups at 100 yards. Depending on how far you want to reach out.....the 175's, generally, are the ones that folks use....say for shooting at 1K.

Good Luck.....I would love to have a .308 with a can on it( you said the 20" barrel was threaded)...but my state doesn't allow it .

Wayne