A little extra velocity may be helpful (but not necessary) in that it flattens out the trajectory and gives a little added range, but it wont promote the cartridge up to being a good deer cartridge.
Bottom-line -- the .25-20 is good for shooting bunnies, skunks, porcupines, coyotes, etc. Whether the intended quarry is intended for the dinner table or simple extermination, will dictate the nature of the bullet/load.
All in all, these pressures and velocities are very comfortable for cast bullets, hence my interest.
A variety of guns have been manufactured in .25-20 over the years, but the one that caught my eye was the sleek little Remington Model 25.
Staying within this pressure range, the 86 grain bullets can be launched at over 1700 fps.For the 85 grain gas-checked 257312, it lists a maximum load of 10.7 grains of 4227 producing 1750 fps.