Classic POA left of center

[alvinSF49]

Hey Skosh

I took my gun to the range today after drifting the rear sight to the right using EPJ's sight pusher. Worked like a charm! It's centered now. I got to the range and set up my target at 7 yards loaded my mags and went for it. Problem fixed. My POA was pretty much where the POI was. I'm happier with the guns performance today, although not satisfied.

This happened next...

After 100 rounds down range I started to have the same problem again. My POI was off again to the left of center? I looked at the rear sight and it walked itself back to it's original position. It's noticeably to the left again. BTW I did tighten the set screw....any ideas guys?