I just noticed that the Antimatter Shells Weapon Modifier actually increases damage reduction as the teirs go up.
For example in the Teir II it is as follows
Mark I
Railguns deal thermal damage. Reduces damage by 1%.
Mark II
Railguns deal thermal damage. Reduces damage by 2.5%
Mark III
Railguns deal thermal damage. Reduces damage by 4.8%+
I’ll also apologize if this isn’t considered a text bug and ask that if that is the case that this thread be moved to the proper location.