Low level players may want to stick with the Avenger, as it has the highest accuracy rating at this level. More damage can be done with the Reaper, but at a significant cost to accuracy.
Shots-before-overheat doesn't vary much for sniper rifles, so mid level players should look to the Equalizer for high damage, the Striker for high accuracy, or the Naginata for a balance of both.
The HMWSR and the Punisher are the only sniper rifles to offer a full 2.0 SBO rating to high level characters. Beyond these, the Volkov is a good choice for dealing high damage.
Ariake Technologies I II III IV V VI VII VIII IX X
DMG Naginata - - - 166 180 194 209 223 238 252
SBO - - - 1.5 1.5 1.5 1.5 1.6 1.6 1.6
ACC - - - 55 56 57 58 59 60 61
Armax Arsenal I II III IV V VI VII VIII IX X
DMG Punisher - - - - - - 226 242 257 273
SBO - - - - - - 1.8 1.9 2.0 2.0
ACC - - - - - - 72 72 73 74
Devlon Industries I II III IV V VI VII VIII IX X
DMG Striker - - - 152 165 178 191 205 218 231
SBO - - - 1.5 1.6 1.6 1.6 1.7 1.7 1.8
ACC - - - 59 60 60 61 62 63 64
Elanus Risk Control I II III IV V VI VII VIII IX X
DMG Hammer 92 103 113 124 135 146 157 167 178 189
SBO 1.2 1.2 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.4
ACC 35 37 38 39 41 42 43 45 46 47
Elkoss Combine I II III IV V VI VII VIII IX X
DMG Reaper 102 114 126 138 150 162 174 186 198 210
SBO 1.2 1.2 1.2 1.2 1.2 1.2 1.3 1.3 1.3 1.3
ACC 24 25 27 28 30 31 33 34 36 38
Hahne-Kedar I II III IV V VI VII VIII IX X
DMG Avenger 82 91 101 110 120 130 139 149 158 168
SBO 1.3 1.3 1.3 1.3 1.3 1.4 1.4 1.4 1.4 1.4
ACC 41 42 44 45 46 47 48 50 51 52
Haliat Armory I II III IV V VI VII VIII IX X
DMG Equalizer - - - 179 195 211 226 242 257 273
SBO - - - 1.4 1.4 1.4 1.5 1.5 1.5 1.5
ACC - - - 50 51 52 54 55 56 57
Kassa Fabrication I II III IV V VI VII VIII IX X
DMG Harpoon - - - - - - 244 260 277 294
SBO - - - - - - 1.7 1.8 1.8 1.9
ACC - - - - - - 69 70 70 71
Rosenkov Materials I II III IV V VI VII VIII IX X
DMG Volkov - - - - - - 261 279 297 315
SBO - - - - - - 1.6 1.7 1.7 1.8
ACC - - - - - - 66 67 68 69
Spectre - Master Gear I II III IV V VI VII VIII IX X
DMG HMWSR - - - - - - 278 - - 336
SBO - - - - - - 1.8 - - 2.0
ACC - - - - - - 85 - - 86