If you haven't got the die yet, do three things:
First, line your cases up on a table or other flat surface using a yardstick or other straight edge along one side to be sure they are in a straight line. Then sight down the case mouths to see if they are also lined up or if they are tilted. The Garand and M14 style bolts and actions are famous for not holding their bolt faces perfectly square, resulting in slightly tilted case heads. Such tilting adds extra length to the case if it doesn't happen to be picked up in the same orientation in which it was fired. If you have tilt, you want to identify the side opposite the direction of mouth tilt and feed that first into your shell holder. If it goes into the shell holder over the high primer groove that most (except Redding shell holders) have under the shell holder mouth, you resize the case shorter than needed because the case isn't pushed at its longest point.
Second, when you set up your sizing die, be sure to use the crack-of-light check. All presses, even the heavy iron ones, have some degree of stretch, and that can short-stroke your resizing slightly. Set the sizing die up, re-lube the case and press it up into the die. Then look sideways at the shell holder deck where the mouth of the die touched it during your die setup. Put a flashlight behind it to make sure there is no crack of light between the deck and the die mouth. If there is, screw the die in another 1/8 turn and try again. When the die is turned in just far enough to make the crack of light disappear, it is fully resizing. Note that it is best to do this check with a case that hasn't been previously resized because that puts the most stretching force on the press, but you go with what you have available.
Third, per Shadow9mm's suggestion, run the case all the way into the die and count. He holds while saying "one one thousand". On a stubborn case, I hold while muttering 1.-2-3-4-5, and then lower the press ram just far enough to use my thumb and index finger to turn the case a third of a turn and then run it back up into the die for another muttering count, then repeat that sequence once more. I can almost always get two or three-thousandths of additional shortening of the case from head to shoulder that way. Also, it automatically handles the tilting height issue I mentioned under "first".
Fourth, if none of that works, take your expander out of the die. Some dies that resize just fine will have their expander balls pull so hard on the neck that it actually pulls the top of the shoulder forward a little, taking the case from just fine to too long at the neck and shoulder junction. If you are having this problem, be sure to be using an inside neck lube. I don't know what die you have, but there are carbide expander balls available for RCBS and Redding and Hornady dies, I believe, and they greatly reduce that tendency. A still better approach is to resize without the expander in the die at all, them use a separate Lyman M die to expand the mouth. Set it so just a sixteenth of an inch of the case mouth will go over the small step in the die. This creates a short wide space that lets you set your bullets in to stick straight up as you seat them. It greatly reduces cartridge runout and visibly improves accuracy. Expanding by pushing down into the neck rather than pulling up is much less prone to distorting the case. But still use an inside neck lube with it. The dry graphite or motor mica dust lubes are fine for that.