FN P90/PS90 RMR mount

thingiverse

Created by a friend. This RMR (Trijicon pattern) mount is designed specifically for the FN P/PS90 and its Airsoft variants. The factory rail on these firearms is too "tall" and this custom mount lowers it to just above the frame side rails where sling mounts or rails can be attached securely. The initial version, v1, was a test piece (pictured in yellow PLA) that was not properly sized for screws but helped finalize hole placement and post spacing. A second version, v2, was designed with brass threaded inserts installed, making it easier to attach the mount to the frame. Version 3 made minor changes after installing the threaded inserts and uses two M2.5x12mm countersunk screws to mount the RMR and four M4 screws to attach the mount to the frame. This design improved stability and security. The fourth version, v4, replaced hollow posts with inserts from the top for M3 screws. The change was made because hollow screw attach points printed with a .4mm nozzle are only one layer wide, making them questionable in terms of strength. To distinguish between v3 and v4 when mounted, I designed a slightly different shape at the rear. For the brass threaded inserts used, two sizes from a set on Amazon were employed: Initeq Threaded Inserts for Plastics Metric Assortment A (SKU IN064548-A), supplied by Albers LLC. To attach the mount to the frame, four M4-0.7 "short" screws (4.7mm long) are used, while two M2.5-.45mm "long" screws (5.56mm long) and two M3- "short" screws were used for v3 and v4 respectively. To attach the RMR to the mount, two M2.5x10mm countersunk flat hex head screws are used in v3, while v4 employs two M3x10mm countersunk flat hex head screws. My friend's factory RMR M1913 mount was used as a reference to draft out the dimensions for this custom mount, which also fits the Holosun 507C or other mounts that fit the RMR pattern. I informed my friend that the surface may not be flat enough for the RMR to use the sealing plate, so they should take necessary precautions.