Re: Advice for loading
If you have not already, break in the barrel.
That said, what is your leade? set your OAL back about 5/1000ths from that.
Use cases from the same manufacturer or made to the same specs.
Fed 210 primers give really good consistency.
IMR 4895 and 4064 are both popular at Camp Perry...
I have had good luck with RE-15 and Varget.
Sierra and Hogden both tend to be conservative, you can get away with going one or two grains higher than the manual states, just be careful and look for the signs of overpressure.
EXAMPLE: for 168gr BTHP, using RL-15, Hornady lists 44.3gr. max, Sierra lists 43.6 and some others found online go as high as 47. (One of my purpose-built rifles shoots best with 44.5gr.)
Try different weights, and manufacturers, A rifle belonging to my best friends wife shoots best with off the shelf Remington Core-Lokt if you can believe that.
Anyhow, get yourself a chronograph, it is flat out the best instrument for verifying consistency in your loads, you will quickly find that the loads that tend to have close and consistent velocities are also the ones that get you your best groups.
Remember you are not looking for your highest velocities, but the most consistent. If you run a batch that is within 10FPS consistently, that one will be your 1/4 MOA load.
Oh yea, expect to load separately for every rifle if you want the absolute best accuracy out of each one.
If you just want a general load that shoots pretty well and is safe for all of your .308s, try 42 to 42.5gr. of any of the above mentioned powders, FED 210 primers if you can find them, and set your OAL to 2.800, you should get 1 MOA or better using a clean broken in barrel.