I measured the maximum COAL of my Encore 308 and found it to be 2.70". At this length the bullet is the lands. I loaded some 168 grain A-max bullets to 2.68". Now my question. How much do you lengthen or shorten the COAL to find accuracy sweet spot. I loaded cases with mid-ranges charges to prevent over pressuring.

Well you'll need to do it with the load you plan on shooting if you use a different charge even with the same propellant it could potentially affect the best seating depth. I rarely use fullpower loads if you need to what you need is more gun. But what is do is load 3 just touching the lands 3 .005 off 3 .010 off 3 .005 into the lands and 3 .010 into the lands and see where your best group is if its at one extreme or the other go .005 more for 3 shots and see if its better or deteriorates once you find the best one go .002 in for three and .002 out for three. Shouldn't need to to .001 at a time unless your planning on doing 600 yard matches with it lol. And really .005 steps is all I would do for a strictly hunting gun.

Be careful if you go to far into the lands it could pull bullets on extraction. I will say though that I almost always get best accuracy just touching to .005 into the lands in my guns. My 223 and 22 hornet barrels will both do 3/8 or better hundred yard groups if I do my job.

COAL is a super-fine tune. Settle on the load you want and then you can adjust the depth. I never seat a full power load into the lands, fireforming yes but not the real deal. I load 10 -15 thou's off the lands and have been good to go, haven't really found the need to play with length much. Heck my AR shoots sub-MOA with 55 grain Hornady's seated to the cannelure, no idea of where it is in relation to the lands. It is fussy about the powder load tho.