Here is how to adjust the Ring Sights.
How to Align the Sights on the FN PS90 Rifle Using the FN Sight Tool
Using the FN sight tool to align the sights on the FN PS90 rifle.
StepsSlide the allen wrench supplies through the sight tool with the short 90 degree section sticking out the top of the widened part of the spanner tool.
Carefully insert the allen wrench into the allen locking screw for the screw controlling the adjustment direction needed. This will be the vertical screw closest to the shooter for vertical adjustments, and the horizontal screw inside the sight riser for horizontal adjustments.
Once the allen wrench is securely seated into the allen locking screw, gently loosen the locking screw.
Turn the spanner tool to adjust the sight alignment of the ring sight.
Clockwise movement of the spanner tool will result in moving the bullet strike up and to the left depending on which adjusting screw is being turned. Counterclockwise rotation will result in the bullet strike moving downward, or to the right accordingly.
These adjustments are fairly coarse, so small movements are recommended.
Tighten the locking screw, and test fire the weapon to verify alignment. Repeat these steps as necessary to zero the firearm.
The adjustments on the Factory Ring Sight are fairly coarse, so use small corrections, test fire and repeat as necessary to zero the firearm
Note: The "adjustment tool" is an absolute waste of $60 or so hard-earned dollars. A 3mm metric allen, in conjunction with a standard choke tube wrench work perfectly fine using the above directions.
Warnings As always when working on any firearm, always keep the muzzle pointed in a safe direction. Never assume that the weapon is unloaded. Verify by removing the magazine, and checking the chamber area that the firearm is unloaded, and again always keep the muzzle pointed in a safe direction.
Things You'll NeedFN PS90 sight tool, or similar manufacture.