6mm ARC

[BluntForceTrauma]

I like Brian Litz's research and according to him there's no downside to "overstabilizing" a bullet. Main benefit is improving the long-range accuracy by keeping a bullet more stable through the transonic zone.

Possible downsides are blowing up bullets, but that's not an issue at any Grendel velocity (and certainly not in the minor difference between 1:7 and 1:7.5). Also, some think there's a velocity loss with tighter twists — and, technically, there is — but Litz's actual testing showed it to be something like 1.33 fps per inch of twist — completely insignificant!

So, MONSTER 20 in 6mmARC is totally within the realm of possiblity.