adjusting the rear site on pistols?

[cajun47]

i never had to do this before but my new ruger p95 seems to shoot to the left a little. i shot 400 rounds at man size targets at 30 yards. i tried different ammo. i have good groupings but its to the left of the chest area.

at 10 yards it shoots perfect. btw its not me cause my ruger p89dc shoots dead center at 30 or 10 yards. i unscrewed the allen wrench thing and took it out but the rear site won't budge at all. do i have to tap it rather hard or what?

 

[GRIZ22]

Tap it with a brass or plastic hammer or drift. My P90 rear sight was a little hard to move but since adjusting it about 15 years ago. Locktite the screw when you put it back in. I've never had to do anything to it since.