Ruger Mini-14 front sights were designed to never come off or get knocked out of line, so they were pressed on TIGHT, and I mean TIGHT.
Usually, when called on to remove one, I had to destroy the sight to get it off. Sometimes, no amount of pounding with a hardwood block and mallet would move it.
The method I finally settled on was to use a slightly dulled cold chisel to cut a groove the width of the sight band on the underside of the sight.
The idea is to dull the chisel enough that instead of cutting through and into the barrel, it actually swages a groove in the band.
This actually stretches the band and allows it to be easily tapped off with the hardwood block or even a large nylon or brass drift.