I copied this from somewhere and kept it as a reference in case I ever wanted to fool with it. My gunsmith told me basically the same thing when I was doing a re-barrel on an M77. He has done some of them (front sight removal) and won't even attempt to save the sight anymore. Others may have different experiences.
"A quick note on the installation of factory Ruger front sights.
The barrel is cooled with liquid nitrogen. The sight is kept in an oven at a slightly elevated temperature. The barrel is placed in a fixture to keep every thing straight and the side is slid on. When the temperatures stabilize, the front sight is there to stay. To the best of my knowledge no adhesive is needed or used.
Over the years I've seen literally 100s of ruined sights and ruined barrels from sight removal.
My method. If I'm going to use the barrel: I cut/mill/file the sight base in two places, 180 degrees apart. When I'm just shy of barrel metal I pop the sight apart with a cold chisel and a SMALL hammer.
If I want to keep the sight and don't care about the barrel: I cut the barrel off behind the sight. Chuck the thing in the lathe and then mill the barrel out from inside the sight.
When you get the sight off, regardless of method the tip of the barrel usually shows some compression. This can be buffed out to blend with the barrel.
Of course if you want the shorter barrel or are installing the flash hider, then just cut it off.
A hack saw works great. ;-) "
