AR-10 is the base for larger calibers that can't fit the AR-15. Anything sharing a .308 parent case is going in a 10 along with other longer calibers. 6.5 Creedmore ,.243, 338 Federal ,6.5 Creedmore ,260 Remington , 243 winchester , 7 mm-08 ,30-06,300win mag ect.
Ar-15's are for shorter cartridges and basically anything that uses a .223/ 5.56 as a partner case ( your stuck to a Max mag length of 2.226" or something like that. .223 5.56x45 5.56x39 7.62x39 300blk 300 Ham'er ,.277wolverine 458 socom .17 rem 6.5 grendel 6 Arc .224 Valkyrie .20 tactical .20 practical 6 grendel .358 yeti the .