Yes, it is indeed the biggest that will fit.
But will it reach out to 800 yards and still be accurate?
I’d say that if you are using an AR platform for long range accuracy, you’ve selected the wrong tool. It is great at medium short ranges, but long range, pick a better one. I fully appreciate that you will have long range touch, and 50 Beowulf will have that mass to make the F=MA formula pretty good. I see the wisdom in accurate fire, take what you’d like. Either, or both really. Upper swaps are trivial.