Help adjusting slug barrels sights

[volk06]

I purchased a rifled slug barrel for my 870 Express. I went out and did some test firing. I was consistantly shooting 8" lower than where my sights were aiming. Which way do I need to move the rear sight and how much does each little line mean? I have to use a small allen wrench and slide it either up or down. There was no manual with the slug barrel.

Also the Winchester 1300 we have has a slug barrel that keeps shooting to high and the sight is adjusted all the way back. It has the lift and slide type of rear sights. Is there any other good sights that I could replace it with to make it more accurate?

 

[Oldwolf]

Rear site up - point of impact goes up
Rear site down - poi goes down
Rear site to the left - poi goes to the left
Rear site to the right - poi goes to the right