The choice of shotguns for low level characters is limited, so players should look for a Scimitar as it deals the most damage: The drop in SBO and accuracy at this level is negligible.
Mid level players should upgrade to a Katana because of its damage, even if it has slightly lower accuracy and SBO when compared to the Firestorm.
High level players that don't have access to an HMWSG should look to the Avalanche because of its extremely high shots-before-overheat rating, or the Sokolov, which does a high amount of damage.
Ariake Technologies I II III IV V VI VII VIII IX X
DMG Katana - - - 197 211 226 240 254 269 283
SBO - - - 4.2 4.3 4.5 4.6 4.8 5.0 5.3
ACC - - - 70 70 71 72 73 74 75
Armax Arsenal I II III IV V VI VII VIII IX X
DMG Avalanche - - - - - - 260 276 291 307
SBO - - - - - - 6.1 6.5 6.9 7.5
ACC - - - - - - 81 82 82 83
Devlon Industries I II III IV V VI VII VIII IX X
DMG Firestorm - - - 180 194 207 220 233 246 260
SBO - - - 4.5 4.6 4.8 5.0 5.3 5.5 5.8
ACC - - - 72 73 74 75 75 76 77
Elanus Risk Control I II III IV V VI VII VIII IX X
DMG Hurricane 115 126 137 148 158 169 180 191 202 212
SBO 3.3 3.3 3.4 3.5 3.6 3.6 3.7 3.8 3.9 4.0
ACC 56 57 58 59 60 62 63 64 65 66
Elkoss Combine I II III IV V VI VII VIII IX X
DMG Scimitar 128 140 152 164 176 188 200 212 224 236
SBO 3.1 3.2 3.2 3.3 3.4 3.4 3.5 3.6 3.7 3.8
ACC 48 49 51 52 53 55 56 57 58 60
Hanhe-Kedar I II III IV V VI VII VIII IX X
DMG Storm 102 112 122 131 141 150 160 170 179 189
SBO 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.4
ACC 60 61 62 63 64 65 66 67 68 69
Haliat Armory I II III IV V VI VII VIII IX X
DMG Tornado - - - 213 229 244 260 276 291 307
SBO - - - 3.9 4.0 4.1 4.3 4.4 4.6 4.8
ACC - - - 67 68 69 69 70 71 72
Kassa Foundation I II III IV V VI VII VIII IX X
DMG Armageddon - - - - - - 280 297 314 330
SBO - - - - - - 5.5 5.8 6.1 6.6
ACC - - - - - - 80 80 81 81
Rosenjov Materials I II III IV V VI VII VIII IX X
DMG Sokolov - - - - - - 300 318 336 354
SBO - - - - - - 5.0 5.3 5.5 5.8
ACC - - - - - - 78 79 79 80
Spectre - Master Gear I II III IV V VI VII VIII IX X
DMG HMWSG - - - - - - 320 - - 378
SBO - - - - - - 5.8 - - 7.0
ACC - - - - - - 90 - - 91