Just did a quick test for the burst settings before going to sleep, seems working well, at least the hit numbers are correct. (Minigun with 1-1 dmg & 1000 round burst, 5mm AP with 1/1 dmg mod, forcing 100% ToHit chance, against unarmored targets)
The divisor/multiplier settings for the primary target is great. The only change I can think of now is making the names of settings shorter.
Will test the build on XP/2003 machines tomorrow if I got some free time during work.
BTW, don't know if you add any check for preventing dividing by 0. And for parameter combinations that would make total bullets usage not equal to 100%.
I think I've added preventives against division by zero. As for the latter, I think we can just drop DivisorCenter parameter and calculate it based on DivisorSides (because normally people will want DivisorSides to be higher, so this will give more flexibility). As for target divisor/multiplier... well I could add checks so multiplier will be capped to be not greater than divisor.