I have two 6.5SSs (and had two others before that). A 20" and a 26". I love them both.
I shoot various bullets in the 20". My main load is a 130 OTM @ 3075fps.
My 26" only shoots the 156 Elite. Either 3003fps w. H1000, OR 3068fps w. N565.
They feed like butter from either a BDL w. Wyatt's extended box and staggered follower (20") or from a DBM w. Accurate WSM mags (26").
I also have a 26" 25SST. I have shot the 131 BJ, 135 Hyb, and now the 133 Elite. All have been between 3120 and 3350. I have kept mine pretty light, around 3188-3230. For deer and pronghorn, I LOOOOVE this rifle! Faster, higher BC, and decent bullet weight.