12.5" Atheris Rifle Complete Upper 6.5 Grendel
Primary Arms SLx6 3-18x50mm Illuminated ACSS-Apollo

To swap out my 9.5 300 Blk Upper on my SBR lower (Geissele SSA-E Trigger) and add my Sig Sauer SRD762Ti Suppressor.

Looking to eventually do some 100-800 yard shooting after getting some time behind the scope at 100-300 once the weather starts to cooperate in GA (Cold, Hot, Rain, Cold, POLLEN, Cold). I know I'll lose velocity with the 12.5, but there are a few factory loadings that are 2300-2400 with this barrel length. Grabbing all the ballistic charts for as many loads as I can with a few boxes of each on order to run initial testing on.

Anyone have an Atheris upper in use already?

Thoughts on the Primary Arms 3-18 for 6.5 Grendel at longer ranges?