Sights are fine but installation was a challenge - Williams Gun Sight Universal 'Ghost Ring' Fire Sight Set

Installation instructions are woefully inadequate and the Williams tech was not that helpful.

I mounted the sights on a Turkish-made Mossberg O/U gun, with a 0.277" wide rib.The sight bases have a pyramidal set of grooves for 1/4", 5/16" and 3/8" grooves. The instructions make no mention that instillation my require shimming, which I was told by the Williams tech. After an unsuccessful attempt to cut shims from a sheet of aluminum, I fund an expired, plastic membership card a bit thicker than an average credit card. a 1/4" strip cut from the card, to fill the narrowest groove in the base, was just thick enough to take out the vertical slop.

Each sight base has four sets of holes to locate the screws, according to the width of the rib. Aligning the screws with the locking block that clamps the sight to the rib is easy enough for the first one, which is loosely screwed screwed in place before setting the sight on the rib. Doing so with the second locking block, once the sight is sitting on the rail is another matter. It finally occurred to me to cut a pointed toothpick in half, for use as a slave pin, to get the holes aligned. Had Williams included that suggestion in the instructions, it would have saved me a couple of hours of frustration.

It also would have been nice had the instruction included disassembly and reassembly of the rear sight, required to access one set of the screw holes.

I zeroed the 20-gauge gun with slugs at 25 yards (with a guesstimate of how high to place hits for an approximate 50-yard zero). With visual centering of the sights on the rib - required because the 5/16" slot is wider than the 0.277" rib - I only had to adjust for elevation.