*IMPORTANT NOTE: CHECK STATE REGULATIONS REGARDING FORCED RESET SYSTEMS BEFORE STAGING YOUR BUILD!*
*CONTACT US FOR A SPECIAL COUPON CODE*
Atrius Development Group X-Series Ambidextrous Forced Reset Selector for SIG MCX / MPX - SKU: ADG-FRS-AMBI-X - UPC: 850079014107
Product Description
The Atrius Development Group X-Series Ambidextrous Forced Reset Selector (ADG-FRS-AMBI-X) is a drop-in 3-position forced reset selector system specifically engineered for gas piston platforms, including the SIG Sauer® MCX®, MPX®, Rattler®, and MCX-Spear LT Upper AR Conversion Kits. Designed by Atrius Development Group, this system converts compatible platforms into a forced reset fire-control setup featuring Safe, Semi-Auto, and Super-Semi (Active Forced Reset) operational modes.
Precision-crafted in the USA from heat-treated 4140 steel and coated in a corrosion-resistant black nitride finish, the X-Series includes a newly engineered FRS lever calibrated for the dimensions of SIG piston product lines. The kit features an ambidextrous selector switch layout with aggressive ergonomics, chamfered edges, and 90° indexing detents for rapid, positive manipulation under dynamic stress.
Operating seamlessly with standard MIL-SPEC AR fire control groups (without relief cuts/U-notches) and select single-stage cassette-style triggers, the X-Series FRS includes an internal trip base and trip clutch assembly. This setup installs without permanent modifications, cutting, or gunsmithing required on the host lower receiver.
*Armorer Bench Notes & Real-World Staging Guidance:
Fitment Matrix: Direct drop-in fit for SIG Sauer MCX, MPX, Rattler, and MCX-Spear LT Upper AR Conversion Kits paired with compatible lower receivers. Works with MIL-SPEC triggers (no U-notch cutouts) and select drop-in cassette triggers. (Early gen MCX models may require safety latch removal). Check all applicable federal, state, and local laws regarding forced reset selectors prior to installation.
- Verify host firearm is completely clear, magazine removed, and chamber visually and physically confirmed empty.
- Install the X-Series FRS selector barrel into the lower receiver selector hole as you normally would any standard safety selector.
- Install your compatible fire control group (trigger and hammer assembly).
- Insert the trip base onto the left side of the receiver and marry it to the rear trigger pin.
- Insert the trip clutch onto the track of the trip base, push it all the way forward, and press the trip base down so it sits under the rear takedown pin.
- Verify the trip assembly hasn't shifted, install the upper receiver, and execute complete dry function checks across all three selector positions before live firing.
Key Features
- SIG Gas Piston Compatibility: Specially dimensioned FRS lever engineered for SIG MCX, MPX, Rattler, and MCX-Spear LT platforms.
- 3-Position Configuration: Provides intuitive selection across Safe, Semi-Auto, and Super-Semi (Forced Reset) modes.
- Heat-Treated 4140 Steel Construction: Military-grade steel build with non-marring chamfered edges for extreme durability.
- Corrosion-Resistant Black Nitride: Advanced nitride coating protects against sweat, rain, mud, and continuous cycling friction.
- No Modifications Required: True drop-in architecture installs into receivers without cutting or permanent trigger modification.
- Aggressive Ambi Ergonomics: Textured ambidextrous selector switches allow rapid thumb engagement from either side.
Product Specifications
- Brand: Atrius Development Group
- MPN: ADG-FRS-AMBI-X
- SKU: ADG-FRS-AMBI-X
- UPC: 850079014107
- Platform Compatibility: SIG Sauer MCX, MPX, Rattler, MCX-Spear LT (Gas Piston)
- Trigger Compatibility: MIL-SPEC (No U-notch) & Select Cassette/Drop-In Triggers
- Positions: Safe / Semi / Super-Semi
- Material: Heat-Treated 4140 Steel
- Finish/Color: Black Nitride / Matte Black
- Country of Origin: USA
