Free bore can be a topic that pertains a lot to psychology more than practicality. I have been in discussions with my Palma friends about this. They have used the Palma 95' reamer with free bore past .080 and a bit shorter than that. I cannot recall exact numbers. It seemed that a little more free bore maybe was an advantage, but they shoot well with lesser free bore distance too. I think there are many sub moa m14's around with a comparable free bore to what you measured. I suspect there is no magic number for the best free bore.I usually use OAL from the manuals.
I’m using Sierra 155 gr. and the Sierra manual lists an OAL of 2.775“. BTW my Hornady manuals all list 2.800 for their 155 gr. bullets. I checked the chambers of my M1 .308 barreled by Fulton and M1A James River/Rockola both Criterian barrels and get a max OAL bolt face to lands of 2.860” +/- a few thousands measurement error.
So this means the free space in my handloads is a whopping .085 thousands. Reading up I see that that ideally around .035 or so is a good number provide the ammunition fits the magazines.
My reloads usually shoot 2 1/2” groups with irons. Is there much to be gained by experimenting with OAL other than wasting ammo?.