whenever i have a particular gun that is hitting at a different POA i have someone else try it to see if it eliminates me or not. If it's not me then i adjust the sights if they are adjustable. If not i see if they can be replaced with adjustable or different heights. If they can't then you switch your POA. The reality is some guns just don't shoot where the sights aim to and can't be adjusted. There are some that can be filed too depending on where it's shooting and how far off. Some of these repairs and replacements should be done by gunsmiths with proper tools too. Almost forgot, sometimes switching ammo can help too.