For that kind of $ you can buy the best of variable power scopes, and there are some excellent 1 - 8X models. At 1X there is no searching for the dot, so IMO, scopes at low magnification, or no magnification, are the fastest on target.
Generally you'll see price go up with highest magnification, particularly when they start at 1X. You might even want to consider a model starting out at 2X if you find you can get on target at the same speed. 300 yards is a practical limit for the rifles capabilities and where having 8X from the same optic allows you to cover almost any distance most of the MSR calibers are capable of. AR10 platforms with greater range capability like say 6.5 Creedmoor, .260 REM, 7mm-08 REM and .308/7.62 are better suited to things that occur past 100 yards, and then, they are somewhat handicapped with shorter barrels.
Chris Kyle left us a fine legacy when he worked with Spec-Ops to create the Mk 262 Mod 0 that's only evolved since then. As a handloaders, my shooting partner and I replicated that load with the Sierra 77 gr MK HPBT with cannelure with Chris Kyles mandate of 2700 FPS at the muzzle. That bullet will tumble out to 300 yards which was the intended purpose. There is a better option for that and close range with the Hornady 75 gr. BTHP. It will not come apart at closer ranges. Either load will need to be 5.56mm NATO rather than .223 REM. Same with handload data, and a cannelure on the bullet is essential in holding the bullet together. They don't exactly advertise it, but Hornady sells a 75 gr. 5.56mm NATO Match load that uses the same bullet as the TAP2. Velocity from a 16" barrel will be 2750 FPS or slightly better, the same as our handloads using Ramshot TAC and Western 5.56mm NATO data. It's a 0 -300 yard load. Having the same capability with your optic should allow you to be quicker getting on target at these same distances.
Almost forgot! Crimson Trace is heavily into the optics market now. They might have the best of everything with a scope that gives you a dot at low magnification that becomes crosshairs with a center dot at higher magnification.
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Anything that can be corrupted by man; will be corrupted.
The Lord is my shepherd; I shall not want . . .