When measuring OAL, you want to use a OAL guage on the ogive, not the tip. Your still going to have variations of .002" or so. Stoney point sells them.

Another tip I do is when seating, don't come down in one stroke. I lay the bullet in the case and raise the ram just to push it in a tad, I then rotate the case about 60degrees, I then push in a tad more and rotate some more. I do this three times.

Also lubing the inside of the case mouths with imperial sizing wax, can help with more consistent seatings.