Minor amounts, I didn't dent the thing in, in fact you could not see or feel any change in roundness, but you could no longer get the male end into the female end. It doesn't take much change in roundness to make them stick.

Like I said, I do not recommend this method in most cases, but on rods that may not be worth the added expense of new ferrules, it was worth trying. In this case it worked, but on a rod of any real value, I would just replace the ferrules.