Too add- seating depths aren't all that important, so long as you don't go too short, or too long- longer COL's will lower pressures a bit, but if you get too close to the rifling, the pressures can increase very dramatically.

Something I read is that bullet seating depth is kinda like setting the timing on a engine, different bullet seat depths allows you adjust when the bullet leaves the barrel at certain harmonic fluctuations in the steel of the barrel, So basically setting your bullet .020 from the lands will not neccisarily give you the best accuracy and a bullet set even a 1/16 of an inch from the lands could possibly give you the best accuracy. I am gonna play with the SAAMI specs of bullet seating staying within the printed minimum and maximum and see what I come up with.

Yes, adjusting the seating depth is something you do once you find an accurate load.

Its done more to reduce the jump the bullet has to make to engage the rifling, so that the bullet has a better chance of starting down the barrel with good alignment. When you get to the point of where you are adjusting in increments of +/- .010" you are just trying to squeeze the last 1/4" reduction in your group sizes. If youwant to use the engine analogy, adjusting seating depths before getting a good load is like setting your timing before installing a distributor.

Ok that makes perfect sense, before it was a little confusing. I totally get in now. thank you. so it would be the best idea to start with a minimum COL?

Best Sphical powder for a 308 is BL-C2. Meters so very nice. And a tad higher velocity than Varget.

Seating depths is not that important for alot of bullets but find it very important for solid shank bullets like failsafe, Barnes, and even TBBC.