According to what " i've read in the past" A2400 is allegedly a bit "Faster" than the old Hercules 2400.........it was suggested to reduce a grain or two and work up........
Its obvious you have no scale to weigh powder nor a chrono to compare velocities to find your answer......
I would guess the lee dippers volume would be the same, however....the new A2400 formula is slightly different according to what i have read and pressures and velocity i assume would be a bit higher.....
If you'r reloading for pistols it could make a big difference if your dipper throws max loads......
I use a lot of A2400 in Heavy cast loads in my 45/70........that being said, they are not max 2400 loads and I detected no velocity differences between the same 24.0 gr in the old H2400 and A2400/500 gr cast bullets all at 1300 fps with usual deviation shot to shot.....
an accurate scale is inexpensive............
Lee dippers will work.......but if that "scoop full " proves to be an inaccurate load in your firearm you will need a scale to proceed further.....
hs4570 ...............your mileage may vary