AS Designs MPX Slip Trip Kit (Rev. 2)

The AS Designs MPX Slip Trip Kit (Rev. 2) is the part that makes a forced reset selector work on the SIG MPX. It is not a trigger and not a selector by itself. It pairs with an AS Designs Arc-Fire forced reset selector or an AR Super Safety, supplying the reset trip those systems need on the MPX carrier. A standard AR bolt carrier presents a trip surface the forced reset mechanism rides against; the MPX carrier does not, so without this kit an Arc-Fire or Super Safety cannot reset the trigger on an MPX.

The kit is built around a heat-treated 4140 steel slip trip in a black oxide finish and a 7075-T6 aluminum slip trip guide with a Type III hardcoat anodized PTFE coating to cut friction. The lever blocker is machined directly into the guide, so there is no separate blocker part to fit. You buy the selector separately; this kit adapts that system to the MPX and its fire control group.

Fitment covers the SIG MPX and MPX-K across all generations, though early-generation guns may need the factory safety latch removed. It does not fit the MPX Copperhead or the SIG MCX. AS Designs recommends a generic mil-spec AR fire control group over a Geissele on the MPX, since the platform is known to damage fire control group components under forced reset use. The kit is not compatible with the Atrius Super Selektor, factory Timney triggers, or cassette and traditional forced reset triggers. Some hand-fitting is normal, and a qualified gunsmith is recommended. Confirm your MPX model and generation, and current state law, before ordering.