In powder burning rifles, it has been found that the best precision/accuracy is obtained when the nose portion is the size of the lands to a couple of ten-thousanths over: +.0002 / -.0000. The driving band(s) at the base should be as close to the groove diameter as possible. However, again you can go oversize a bit but not under size.
In your case I'd try to find a mold and alloy that gets the nose to 0.2491 and the base to 0.2552. If the base is bigger when you get the nose to size you can bring the base down by sizing.