Russ - you need to post this in the Blackpowder/CAS section - you'll get a better response.
All depends on what your are using as well - FFG or FFFG? Reall BP or substitute?
While you are using a .457 ball - just remember that you'll probably just get a bigger "ring" of lead when seating the ball than with the .454. Your cylinder chamber throat will determine what the final diameter of the soft lead ball is when seated. Throat size varies sometimes on different brands of guns so sometimes a .454 is "adequate" and sometimes you need to go larger.
Lymans Cast Bullet Handbook (3rd Edition I believe) for a Lyman .44 NMA as:
20 gr. FFG - 555 FPS
35 gr. FFG - 775 FPS
20 gr FFFG - 665 FPS
35 gr FFFG - 785 FPS
I have shot BP C & B for 50 + years - lots of different pistol models. C & B are no different than any cartridge handgun you're loading for. Start on the low end and work your way up until you find what shoots best out of your individual revolver. Just because you "can" load a heavier charge, does not mean that the heavier charge is what is the "best". Develop you load and shoot what works best without exceeding the maximum load recommended. Do you have a manual that came with your pistol? If so, it should say. Using any more than necessary to "get the job done" is just a waste of powder.
Also, if you are new to BP, make sure you seat the ball sufficiently to compress the powder lightly leaving no air space. Whether you use a wad under the ball is up to you. Some use wonder wads - in my Navies, I use a 1/8" leather wad soaked in lube. Be sure to use a good BP lube over your balls once seated. The BP lube is necessary to keep the fouling soft as you shoot.
Good luck. The Mods will probably shift this over to the BP/CAS section.