From my looking around it appears that 6.5 barrels are really picky as to the ammo they like.
Edit:
These are internet loads as I was just seeing what powders everyone was using but here are some of my notes regarding 6.5 accuracy loads.
6.5 loads may not perform in each barrel.
Powders
ar comp
cfe
8208xbr
6.5G 123 A-Max
-28.5 grains of IMR8208XBR, Lapua cases, Wolf small rifle magnum
primer seated to 2.250 (pressure signs work up)
-31-31.5, 31.2gr CFE
-27-28, 27.4, 27.6 grains of AR Comp
6.5G 100 A-Max
-34.0 grains of Hodgdon CFE223
6.5G 129 SST
-30.8 grains of CFE223
120smk
-28-29 grains of TAC
-29-30.5, 30 grains of 2520 CCI 450
-28-29, 28.5 grains of 8208 XBR CCI 450
-31.7 of BL-C(2)