The problem with sight pushers and round barrels is that there is nothing to clamp to/against that won't keep the pusher from moving when the pusher pad contacts the sight. On a sight in a ramp, or even an octagon barrel, you've got a flat surface to brace against. Best bet on a sight directly in a round barrel is a padded bench vise and a brass tipped punch with an eight ounce ball-pein hammer behind it.
“You can have peace. Or you can have freedom. Don't ever count on having both at once.”
― Robert A. Heinlein