6mm ARC

[BluntForceTrauma]

OK, I'll take a swing....

Is your primary use hunting? The 6.5 Grendel is an AR15 hunting cartridge with long-range target capability.

Is your primary use target shooting? The 6mmARC is an AR15 long-range target cartridge with hunting capability.

For long-range target shooting, 6mm bullets give you better BC for the same-weight 6.5 bullets, or same BC in lighter weight bullets. This means less recoil and more velocity — all wins for target shooting. Same argument PRS shooters will make in favor of the 6mm Creedmoor vs 6.5 Creedmoor.

Huge plus, in my mind, for 6.5 Grendel is Wolf steel-case. I got no problem shooting it even in my original cut-rifled Satern barrel cuz of the conclusions of the Lucky Gunner tests (don't go nuts with mag dumping and you'll be fine!).

I think I'd boil my argument down to this: 65G has heavier bullet mass for more smack on big game. 6mmARC has better external ballistics with even less recoil than 65G.

If you already have one you don't NEED the other. But what do you WANT?