Here's my information and interpretation of the high damage 1-shot capable sniper rifles.
E24 SASR- pros- semi automatic, huge magazine cons- widest hipfire of the 3, least damage of the 3
Aresk-07- pros- tighest hip-fire, one-shot silenced capable cons- bolt action, small magazine
IMP-S- pros- explosive rounds penetrate walls, one-shot silenced capable cons- bolt action, heaviest of 3 sniper rifles