Re: Thinking about first AR...
You're biggest challenge is going to be shooting ANY semi auto into sub MOA at 300 yds with that optic.
A talented semi auto shooter with a sub MOA (100yd rifle) at 500 yds might be able to drop 5 rounds into 3 inches....and you might not be able to shoot the exact same rifle into a 6" group at the same range.
It's not the rifle, it's the level of experience with a shooter and the platform. It's exponentially more difficult to shoot VERY WELL with an AR platform, than it is to shoot with a bolt gun.
There are lots of AR15 rifles that will shoot sub MOA at 300 yds...and I mean LOTS. Don't get discouraged if you're not able to do it...the AR's are VERY different than bolt guns.
Everyone here talking about their guns shooting MOA or Sub MOA, are usually talking about 100 yds, where they can use their optic to control the situation. The farther out you get, the more your optic plays a role.
Your choice, is not what I would choose to shoot SUB MOA at 300 yds.
Will it work? Sure, if you know what you're doing...but the job will be easier with my 5.5-22 Nightforce (OR many others), simply because it has more zoom and better glass.
My point, is that whatever you choose, may or may not be the limit of accuracy.
If you can shoot MOA or SUB MOA at 100 yds...then the only thing limiting you at 300 or 500 is your experience. The gun can do it.
The days when AR15s were considered LESS accurate than a bolt gun, all but over.
An off the shelf AR, can be equally as accurate as an off the shelf bolt gun.
"We do not rise to the occasion...we fall to the level of our training."