There are a lot of guys here who know much more about cast bullets than I do, but I'll throw some stuff out there for you since responses aren't showing.
Hornady's 250-grain XTPs are .452" and that might be a part of the reason they aren't working well for you.
Bullets cast of harder alloys tend to drop from the mold with slightly increased diameter. That's one way to increase diameter and maybe, possibly get a tighter chamber mouth fit, but that's not an automatic way to get best results because harder alloys can pose other problems depending on the situation. The increases in diameter seen with harder alloys are pretty limited.
If you're having to push bullets through the chamber mouths of your revolver, then the diameter should be just about right. I would avoid reducing diameter when sizing and lubing if that's the case. Lube-and-size dies come in many diameters, so you should select one that won't spoil a good chamber mouth fit.
One thing that should be understood is base obturation. When the cartridge is fired the base of the bullet is subjected to a lot of pressure, and that pressure can and should cause the bullet's base to fill out the chamber mouth and seal it. If the seal is not good, then pressure can escape around the base of the bullet and essentially erode the bullet's surface and that leads to leading. Sometimes you may need to harden a bullet to inhibit leading due to higher velocities but there is definitely such a thing as too hard. Hardness needs to be balanced for the application and circumstances and obturation is a part of the equation.
In the same vein, powder selection can be an important contributor to success (or failure). Using a faster burning powder to achieve a desired velocity is sometimes the way to go because the base of the bullet receives a very rapid "kick in the butt," encouraging it to seal the bore. Using a light charge of a slower burning powder to achieve that same velocity might not provide the obturation needed---and you end up scrubbing lead out of the bore. Taken all together, it's a balancing act between pressures and burn rates and alloy hardness, as well as bullet diameter being optimal. I'm sure there are a lot of other things that should be said...but I've been yabbering long enough here...
Hope this helps.
