Out to 50 yards my Pardner 28" mod 12 gauge shoots winchester bulk rifled slugs (15 round boxes) behind the front bead when the bead is just over the receiver. So for elevation I place the bead on the bulls eye or deer vitals and pull the trigger. For windage (left/right) I center the bead over the hammer. The top of the reciever didn't have a good reference point so my shots horizontally strung. When keeping the bead centered over the cocked hammer my shots were perfect left/right. 25 yards the slug it a little, maybe an inch or so higher.
I'm going to switch to brenneke slugs this year in my pardner because of the better slug performance I've seen over the years. And they're supposed to be very accurate and have less recoil. So I'll see if my pardner likes them.
Also, since my pardner shoots both slugs and shotloads a little low at 40 yards, last turkey season I took a pair of pliers and removed the front bead and replaced it with a red truglo fiber optic bead. Now it's like a "reddot" in that I just put the red fiber on the target and that's where the slug is going at 40 to 50 yards. In closer it's an inch or so higher.
But, your pardner may shoot high/low/left/right so it's best to run some slugs through it to not only find where it's shooting but also what your accuracy range is with the slugs you select.
Hope this helps!
later,
scruffy