Originally Posted by
Semisane
It's not often that one wants to bend a barrel. But in those rare cases when it's impossible to drift the sights far enough to bring the point of impact to where it's needed, bending the barrel may be the only way to correct the problem.
Using a hefty C-clamp as illustrated below is a a safe and easy way to get the job done in small increments.

I have a 10ga ml shoots low how big block to start with ? need raise pattern center 6in @ 16 yds