Just got a 20 ga. Mossberg 500 Slugster with iron sights and a synthetic stock the other day with Hornady SST slugs to go with it.

Fifty dollars in ammo later, it shoots about 6 inches high at 25 yards with the rear sight moved down as far as i can get it.

What do i need to do to get it to shoot lower?

Do i need a different rear sight that can adjust lower? Does my gun just not like the Hornadys? The box says they shoot at 1900 fps...should i get some slugs that shoot slower or just try a different brand?

Any help would be appreciated!