So I play R6 Siege the most out of any other game, and would like to use my sensitivity there as a basis for everything else. 

My settings are 12/83 for my hip/ads. The thing is, if I try to convert any game using the hip with ads setting, no matter what I change the 83 setting to, the end result on the ADS is always the same number.

Then if I try to adjust by ADS sights, I get different numbers if I go Acog to Acog, vs Iron sight to iron sight... Anyone know the best way to go about converting ADS sensitivity from siege to anything else?

When you convert using any "All" aim, the hipfire sensitivity is the source for all calculations. The only reason you have to specify the ADS sensitivity is so that the xfactor sensitivity for R6 can be calculated as well. If you want to convert directly from R6 ADS to another games ADS, you must select the "Iron sight / Red Dot / Holo" aim to convert from.

Also R6 is actually quite bad as a source since the sensitivity for the sights like ADS and ACOG are not related to each other, meaning you can't find a conversion method that will match both of them. They scale completely differently, which is an issue for people used to their scaling since you can't have the same scaling in most other games.

For games that do support scope specific sensitivity you'd have to manually convert from and to each scope (for instance R6 ADS to 1X and 2X, then ACOG to 3X, 4X and 6X).