Here is a pic of a .25-06 case sized with no expander with a 6.5 mm flat base bullet seated. If you can find damage on that bullet I must be legally blind.
Forgive me, but I'm in awe that you do not have damage to the bullet? Because you must have a tremendous seating pressure to overcome, it clearly shows...and to be using a flat based bullet, too? Look closely at the case neck...see how the forward portion of the neck expands outward in the area where the bullet was seated. And, look closely at the rear of the bullet itself, notice how it is "polished" from the pressure of seating the bullet. This may work for you, but I would not dare seat my match ammo this way.
I do not use an expander ball for most of the reasons stated herein, But, I do use an expander mandrel on the case neck right when it is just out of the FLR die. This gives me smooth and light seating pressure and cartridges pleasant to look at.
Dan