Not surprising to me, my 16" 308 is ready for 1200yds.
I like the 6.5 CM and have auto and bolt, but the 308 with new components has no problem keeping up. I'm running 168 ELDM 2756 fps and 208 ELDM 2442 fps in 16" 308 AR 10 that weighs 6 lbs without the scope, with excellent accuracy.
Either caliber will do the job...