The basics aren’t especially complex complex but getting int overflow like this is special.

The basics:

All ‘types’ of damage modifier are multiplicative to each-other but only additive with multiple instances of the same type. Base Damage x Multishot x Critical x Elemental Damage x Faction Damage x Enemy Weaknesses

Example:

• You’ve got a gun that does 100 puncture damage/shot with a 10% crit chance for x2 damage
• Add a Base Damage mod (ex Serration) for 100 * 1.65 = 165
• Add a multishot mod (ex Split Chamber) for 90% chance for 2 shots per shot, meaning average damage is now 165 * 1.9 = 313.5
• Add crit chance mod (ex Point Strike), for x2.5 critical chance: 10 * 2.5 = 25% crit chance
• Add crit damage mod (ex Vital Sense), for x2.2 critical modifier: 2 * 2.2 = x4.4 multiplier
• Multiply your likelihood of a crit by your modifier: 0.25 * 4.4 = 1.1. Multiply by your average damage then add it to average damage: 313.5 * 1.1 = 344.85, 313.5 + 344.85 = 658.35
• Add elemental damage for the combo element your target faction is weak to (we’ll use magnetic for Corpus in this example, High Voltage & Rime Rounds) for +(x0.6 + x0.6 = x1.2) elemental damage. So, now your 658.35 average puncture damage shot gains an additional 790.02 magnetic damage for a total of 1,448.37
• Now add a faction damage mod (ex. Bane of Corpus) for x1.3 damage, 1778.7 * 1.3 = 1882.881 average damage
• But wait there’s more! Since you’re doing Puncture and Magnetic damage and both of them do x1.5 damage to Corpus you’re really going to do 2824.3215 average damage per shot, overall a bit more than 28 times the original damage of the gun.