I would recommend a bolt made for 6.5 for best results.
Yes you can. The previous "expert" opinion didnt understand your question! You can use a regular AR-15 BCG and change bolts for 6.5 Grendel, .458 SOCOM, .300 blackout etc, as long as you use the appropriate bolt for the caliber you're using. The only BCG that will fit an AR upper is your standard 5.56 BCG. Just change the bolt, barrel and mag for whatever caliber you choose that will fit in the AR-15 platform.