Is it possible to hunt big games using an AR 15?

[Colorado Osprey]

I have used and own an AR-15 upper chambered in 6x45. 223 case necked up to 6mm. The easiest of wildcat. It only requires a barrel change. Mags, bolt face are stock.
Deer and Antelope but mostly coyotes. I would not use it on elk. When you reload bullets are available from 40 grain to 108.
Interestingly enough more velocity using the same bullet weight when compared to 223. Because there is less bearing surface shooting the 6x45 vs the 223 in say 55 grain you gain almost 100ft/sec with the same powder charge you would use in the 223. It is even more obvious when you compare 77 grain 223 and 80 grain 6x45 where the 223 cant get to 2900 ft/sec and the 6x45 with a heavier bullet will easily reach 2900 ft/sec.