Please do not cycle the rounds over and over again. Bullet setback in .40 can lead to extreme pressure spikes which can blow up the gun.
please read this article.
Beware: Bullet Setback and rechambering of .40 cal duty ammo

This problem seems to manifest itself in .40 more than any other caliber. The .40 operates on a large pressure spike like .38 super. Look at the rounds and over time the bullet will begin to look deeper set in the case.