Well, I was out shooting my 870 Express last week, sighting the Scattergun Technologies TracLoc GRS in for slugs at 50 yards. This type of sight is kind of a trial and error method of sighting in, you get your POI, you loosen the sight bolt, move the sight, then tighten it and fire again.



(1991 Remington Model 870 Express Magnum with Scattergun Technologies Trac Loc GRS.)
Turns out the sights are cast. I didn't even tighten it that much and they broke. I'm sure I could get a replacement part from Wilson Combat, but I'm impatient, so I though I could just make my own.  



(Rear sight before it broke.)
It's a fairly simple sight, but the GR aperture has always kind of
bothered me, because it's more of a long tube than a ring. It's a tube
for structural reasons, since the entire sight assembly is cast. But this design isn't a true ghost ring in use.



(View through SGT GRS.)





I already had a few XS Sight Systems ghost ring sight assemblies lying around, so I started to think about using their aperture in place of the SGT sight. This would be far too bulky, and probably fragile, so I decided to make a rear sight base for the XS GRS assembly that fit the WC/SGT screw hole spacing. The hole spacing on the SGT GRS is a lot further apart than the XS GRS base.



(XS Sight Systems Winged Shotgun GRS. The base has the wings, the GRS assembly mounts on top of the base. One bolt holds the base on the receiver, one bolt goes through the base and sight assembly. There is also a stud at the on the bottom of the sight assembly at the rear that goes in a hole in the base.)





So I made a base out of a piece of scrap picatinny rail. The SGT sight used 6-40 screws to bolt to the receiver, and the XS uses 8-40s.



(4 holes, in order, left to right: Countersunk screw hole for receiver bolt, hole for sight stud, tapped 8-40 hole, countersunk screw hole for receiver bolt.)





I made the base so that the sight is attached to the base by an 8-40 bolt. The stud also indexes into the base.



(Sight base with XS Sight assembly in place.)







(rear of base with sight assembly in place.)



 

Rear.






Front.






Bottom.



























It's obviously not finished, but it's workable.

Nice...

another project for the project thread