All snipers have the same gun ability if you have at least a +1 bonus with it:
Snipers have advantage instead of disadvantage on attack rolls at long range.
Barrett-50 : 130 Gold
1d10 Piercing, 300ft (450ft) Range
(1 Shots Until Reload)
RMB-93 : 180 Gold
1d12 Piercing, 400ft (650ft) Range
(1 Shots Until Reload)
M21 : 235 Gold
1d20 Piercing, 800ft (1000ft) Range
(1 Shots Until Reload)