ChileVerde1
After several decades of tweaking scatterguns and a file cabinet drawer full of things that DID NOT work, my first question I ask myself when considering adding things to perfectly good scatterguns is WHY! What will this do for me and my shooting ability.
If you are considering adding something to your factory perfect scattergun, to make it do something that it can't do now, THEN stop and consider it carefully before proceeding.
I have spent a bit of time here on this forum discussing the limits of scatterguns, and trying to interject what little wisdom is still left in me. The first thing that is on my list is that SCATTERGUNS are not RIFLES. With all of tricks out there and all of the effort and expense, scatterguns are mediocre rifles. Like the "brown Bess" smooth bore guns are 50yd weapons and sometimes that is a gift.
If you are thinking about installing Ghost Ring Sights to extend the range of your scattergun with slugs, OK.
Here are some things you are giving up;
1st - The quick pointing ability of scatterguns at close range combat. (the very thing that makes the gun so valuable.)
2nd - The destruction of the gun's qualities of leading and sweeping. (what you do when shooting moving targets.) For the average shooter the ghost ring will lock your focus in place, that's one of this sights advantages.
Everything is a trade off, if this is a fair trade for your needs then OK.
IF however you are considering mounting this type of sight to make your scattergun POINT better. Then reconsider this project. Trust me when I tell you that the QUICKEST mounting and pointing of this gun is a bead sight just like you have. Anyone that attempts to tell you differently is either TOO TACTICAL-COOL or is a VERY exceptional shooter.
If you just have to have one, the I tend to agree with Lee, I really like MMC GRS sights, another brand that Has been very effective is TRACK-LOCK offered by Wilson Combat.
By the way Dfariswheel MMC has been in the business of mounting scattergun sights LONG before Wilson Combat bought out Scattergun Technologies, a company I did some work for.
From what you described you own a 870 express, if I were in your shoes I would buy a rifle sighted barrel remove the rear sight and then do the math to correctly mount the ghost ring on the receiver. That finish is very difficult to repair or match well.
Good Luck & Be Safe