The twist will vary with the caliber:
Twist = 150 X D2/L
Where:
D = bullet diameter in inches
L= bullet length in inches
150 = a constant
This is called the Greenhil formula and the constant changes at 2800 FPS to 180
for practical use you need to understand that with a round ball the ideal twist for a 54 is about 1 in 80 and the ideal twist for a 50 is about 1 in 70 for hunting loads and to get the best trajectory. Will a 1 in 48 shoot accurate in both? The answer is yes but with a reduced powder load of about 90 to 110 gr some have had to go down to 85gr this will work fine for target to 100 yds but for hunting I prefer the correct twist and a max load that will shoot good. Will a 85 gr load take a deer? Yes but he will usually run farther with a 50 with a 54 you still have a quite a bit of impact or shock or foot pounds of energy just not as much.