6.8 resizing to 6.5 cm?

yeah, no

6.8 SPC
Neck diameter0.298 in (7.6 mm)
Shoulder diameter0.402 in (10.2 mm)
Base diameter0.421 in (10.7 mm)
Rim diameter0.422 in (10.7 mm)
Rim thickness0.049 in (1.2 mm)
Case length1.667 in (42.3 mm)

6.5 creedmoor

Neck diameter.2950 in (7.49 mm)
Shoulder diameter.4620 in (11.73 mm)
Base diameter.4703 in (11.95 mm)
Rim diameter.4730 in (12.01 mm)
Rim thickness.054 in (1.4 mm)
Case length1.920 in (48.8 mm)