To follow up, 25.5 of TAC will fill up way more than 75% of the case I'm afraid. I was only able to get 28.5 grains TAC in the case up to the neck. I stopped at the neck as this is about all the case capacity you can use loading to magazine length in an AR platform, which I think you are. In fact, loading a 75 grain bullet to a OAL of 2.25", I probably can't get 28.5 grains TAC in the case...
Do not interchange .223 and 6x45 data with similar bullet weights.
Another thing, based on the data from Johan, which is probably somewhat accurate as far as velocity, and not sure what your bbl length is, I'd feel safe in assuming your load of 25.5 TAC with a 65 is way under a 3100 MV unless you have a really long barrel. Based on the velocity numbers above from Johan, if the starting load of 26.1 of TAC with a 60 grainer yields only 2800-2900, you using 0.6 grain less with a heavier bullet will be even less than these figures, probably 2700-2800 also dependent on bbl length as these numbers are for a 20"er...
That said, with a Vmax that has proven to be a reliably expanding bullet way down on the velocity level, killing is a non-issue with the mild velocity loads that i think you're running with your tack driving load above...