Mounting a scope on the PS 90 for +-$25.00 - FN FiveseveN Forum

Mounting a scope on the PS 90 for +-$25.00 - FN FiveseveN Forum

Posted by schmidtbender:

I don't think much of the as issued sight. In fact it is clearer with my glasses off than on. I got to thinking about putting a real scope on it and like a true shadetree gunsmith, I "figgered it out".
You need:
1. A 1"x1"x1" piece of square steel "tube" about 1.3" long
2. Two metric allen set screws that fit the existing holes in the side of the sight housing. Take along one of the sight mounting screws as it's the same thread. (I bought four and used the other two to plug the other two holes in the wings).
4. A piece of tip off mount adapter rail from Brownells (see picture).
5. A scope with a tip off mount. You can get the rings in 3/4", 7/8" and 1" for sure on ebay or from Brownells. This is NOT a Weaver crosslock ring set, it is the kind designed for 22s with grooved receivers.
6. Drills, taps and a belt sander

one: remove the existing sight and put the front screw back in (so you don't lose it).
two: Measure the distance between the sight guard ears.(See pics) It was a RCH less than 1" on mine, hence the belt sander.
three: Get it to where it is a press and tap tap fit between the ears.
three: Level it with the flat where the rear OEM sight screw hole is.
four: Drill a 1/8" hole from each side thru the existing tapped hole in the sight wings. Do not drill thru the steel tube, it's just to locate the set screw.
five: Put in the two allen set screws and tighten a bit. This is not a 416 Rigby so be gentle.
six: Cut the Brownell rail to the length you want, drill & countersink a hole for the original rear sight mounting screw in the original hole.
seven: Install the rail with the rear screw and center it on the 1" tube piece. I used a caliper to measure the gap between the rail and the sides of the wings.
eight: Tighten down the rear screw making sure the rail does not move.
nine: Drill a countersink in the rail for whatever screw you use to secure it to the 1" tube. I used an 8-40 scope mount torx. Drill thru the rail with a clearance drill enough to spot the tube.
ten: Remove the rail and D&T the tube.
eleven: cleanup and degrease, mount the rail with blue locktite.
twelve. mount the scope.

My rig has a Leupold Alaskan 6X which is a 7/8" tube scope.
The cheek weld is much better that the OEM sight and I'm just a normal guy that can pick up almost any off the shelf rig and it fits.

To the range tomorrow. I may need to shim the front or rear base a bit for elevation but at least I'll be able to see that target.