little help
If it drifts out, I would use a good brass punch and a dead blow hammer and drive it out left to right. You may have to strike the punch pretty firmly to get the sight to start moving. Ease up after you get the sight to start. Drive in the new sight right to left. If it is very tight and the sight still won't budge, I have used a propane torch to heat up the sight base slightly, just enough to have it expand enough to allow the sight to be driven out. Just be careful and use only enough heat to warm it up good and not to make it change color. Sometimes the dove tail has been peened to tighten it up and now and then you find one that has had loctite put in it to tighten it up. Either way, the heat will usually break the sight loose. Make sure to check for any pins that need to be removed before the sight can move. Good luck with it.