Iron sights are like scopes. You have to sight them in. Some times they are rough sighted in at the factory for a certain load. You will not know if it is right until you shoot it with the ammo you intend to use. Generally, but not always, iron sights are good for windage, but not for elevation. There are just too many variables. Shooting irons at 125 yards depends on the sight construction/type and the abilities of the shooter. If you are up to it and have proper sights; 125 yards should not be a problem with irons. If you have sight handicaps like I do. I am near sighted have astigmatism and need bifocals (you have to do things differently when you start getting long in the tooth), there could be a problem. You could just go out and purchase a new/better scope, that is what I would probably do. I would not get a high power scope. I would get a 2.5X or 4X scope and get the best one you can afford. If all you can afford is a cheaper one then get a "shotgun" scope of the same power I mentioned. They are generally set at 50 yards for parallax and usually built fairly solidly.