I bent a set of Ithaca Flues barrels that shot way low. I put them on blocks of wood at the ends and bounced my weight on them with one foot. It took quite a bit to set the bend. They kept springing back but I got them bent and problem solved. It is very hard to detect the bend. It doesn't take much to move the pattern. And no harm to the solder joints.

I will say that I usually wouldn't resort to such crude methods but the Flues came in a box lot from a farm auction. My father's paid six dollars for the lot.