Even with factory ammo, I would still recommend that you try different bullet weights to see if there is a barrel preference.
Since you have had good results from the FGGM Berger 185s, you might try other FGGM alternatives.

FGGM 175 gr SMK or Nosler CC might show different results and should perform about the same, but one of my .308 shoots the SMKs slightly better than the Nosler CC version.
FGGM 168 gr SMKs shoot better than other factory ammo in my other 308.
I never suspected what the rifles would shoot best until I tried different bullet weights.