The system I use for T2K makes extreme range sniping viable because of all the potential bonuses to the to-hit roll. Bipod, scope, time taken to aim, spotter assistance, spotter's scope, whatever range-finding equipment is available, etc.
In practice though my players rarely had their characters attempt the extreme range shots. They'd often have a sniper or two on overwatch where circumstances allowed but that tended to be at no more than medium to long ranges.
There's no accounting for the occasional amazing dice roll though. I could sit here for hours listing some of the crazy lucky hits achieved in campaigns over the years.
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 "It is better to be feared than loved" - Nicolo Machiavelli
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