Another point to understand is why is 300-460m considered the range for assualt riifle cartridges? Because that is as far as most people can see and determine that a individual is armed and a threat with the unaided eye. DMR guns with optics allow the marksman to engage key targets and particle targets with greater effect to longer ranges generally 600m. The higher skilled sniper will engage out to 800m (7.62mm), 1200m (.300 WM) or greater. These are generally limited to the quality of the ammo, weapon and shooter.
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