AS Designs MCX Slip Trip Kit

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

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 (Teflon) coating to cut friction. The lever blocker is machined directly into the guide, so there is no separate blocker part to fit when running a Super Safety or Arc-Fire. You still buy the selector separately; this kit adapts that system to the MCX and its standard AR or Geissele MCX trigger group.

Fitment is caliber-specific. The kit runs on the MCX in 5.56, 300 BLK, and 7.62x39 across all generations, though early-generation guns may need the factory safety latch removed. It does not fit the MCX in .308 or .277 FURY, which use the heavy slip trip, and it does not fit the 9mm MPX. It is also incompatible with the Atrius Super Selektor, factory Timney triggers, and cassette or traditional forced reset triggers, and AS Designs notes that a Super Safety should not be paired with the MCX or MPX-specific Geissele trigger. Some hand-fitting is normal for the install, and a qualified gunsmith is recommended. Confirm your MCX caliber and generation, and current state law, before ordering.