While I am not suggesting at this point in your reloading experience you deviate from the reloading manuals, you will find with experience that changing the COL is a variable you can use in trying to find the best accuracy. Consistent COL is the best way, but only within several thousandths. But....
What is important in the search of accuracy is consistency. Measuring the COL from bullet point to the end of the case is not an accurate way to get consistent results. What is important is how far the ogive (curved part of the bullet nose) is from the start of the rifling in the barrel. To accurately measure that you need to use a bullet comparator:
It slides onto the bullet nose and is sized to the rifle bore. You then measure the length of the case with the comparator installed and make all rounds match that measurement within a couple of thousandths. To calibrate this process, seat one bullet on a case to the manual COL then install the comparator, measure it, and that becomes your reference number you try to make all others match within a couple thousandth. I think you will find it easy to do.
The manufacturing process for bullets is such that the OAL of the bullet itself is not all that controlled but it is well controlled if you use the comparator on the bullet. Any excess material in the bullet ends up in excess length in the nose making COL measurement seem erratic when the comparator measurement may show very high consistency.