I know of at least one guy on here that has used the 6.5 grendel on deer. You can find pictures on the bragging board. Seems like it worked for him just fine. My brother has one in a ar nice shooter. Only downside is it is not as popular as 6.5 creedmoor so it can be harder to find.243 has been around longer so probably not that hard to find. Of course if you get a Tc encore you can get both calibers and then some ... food for thought.