Atrius FRS MPX Upgrade: Installation & Performance
Atrius FRS MPX Upgrade: Installation & Performance. Install the Atrius forced reset safety on your SIG MPX: legal FRS upgrade guide with installation tips, compatibility notes, and rate-of-fire testing. { "@context": "https://schema.org", "@graph": [ { "@type": "Organization", "@id": "https://greyhive.com#organization", "name": "Greyhive", "url": "https://greyhive.com", "description": "Greyhive is a censorship-resistant video platform for the firearms, 2A, hunting, and outdoor industries — where creators build, review, and monetize unfiltered content.", "logo": { "@type": "ImageObject", "url": "https://greyhive.com/static/uploads/images/ae198483-01c9-44b4-a16a-03f516ceaf66.svg", "width": 512, "height": 512 }, "sameAs": [ "https://x.com/greyhive", "https://www.instagram.com/greyhive/", "https://www.youtube.com/@Greyhive", "https://www.linkedin.com/company/greyhive/" ] }, { "@type": "WebSite", "@id": "https://greyhive.com#website", "url": "https://greyhive.com", "name": "Greyhive", "description": "Greyhive is a censorship-resistant video platform for the firearms, 2A, hunting, and outdoor industries — where creators build, review, and monetize unfiltered content.", "publisher": { "@id": "https://greyhive.com#organization" } }, { "@type": "Person", "@id": "https://greyhive.com/c/tactical_advisor#person", "name": "Tactical Advisor", "url": "https://greyhive.com/c/tactical_advisor", "description": "Tactical Advisor is a Greyhive creator producing original 2A, firearms, hunting, and outdoor content.", "image": "https://greyhive.com/lazy-static/avatars/ae887004-ca3b-4429-a454-d8e4da1facb8.jpg" }, { "@type": "Article", "@id": "https://greyhive.com/blog/atrius-frs-mpx-upgrade-install-guide#article", "isPartOf": { "@id": "https://greyhive.com#website" }, "mainEntityOfPage": { "@id": "https://greyhive.com/blog/atrius-frs-mpx-upgrade-install-guide" }, "url": "https://greyhive.com/blog/atrius-frs-mpx-upgrade-install-guide", "headline": "Atrius FRS MPX Upgrade: Installation & Performance", "name": "Atrius FRS MPX Upgrade: Installation & Performance", "description": "Install the Atrius forced reset safety on your SIG MPX: legal FRS upgrade guide with installation tips, compatibility notes, and rate-of-fire testing.", "articleSection": "Firearm Parts & Upgrades", "articleBody": "The Atrius FRS MPX upgrade is a forced reset trigger system that drops into the SIG MPX, MCX, and most of their variants using the same skill set required to swap a safety selector. It runs about $300, installs in minutes, and — critically — it is completely legal. Every round fired requires a separate trigger pull. The reset just happens faster. In his hands-on install and range test on Greyhive, Chris from Tactical Advisor walked through the Atrius X series on a SIG MPX submachine gun build, including two installation gotchas that will make the system malfunction if you don't catch them first. \"MPX is already a great platform,\" he said, \"but Atrius has made it a must-have.\" What follows is the compatibility list, the install steps, the two parts that cause problems, and how it actually shot across 200 rounds. Key Takeaways The Atrius X series FRS fits the SIG MCX, MPX, PCC, and K variants — but not the Copperhead. Price runs roughly $300 , which Tactical Advisor expects to drop as FRS systems become more common. Cassette-style drop-in triggers (including Timney) are not compatible — the housing physically interferes with the FRS. Remove the rubber anti-wobble/anti-backlash insert under the safety selector, or the FRS will malfunction. Function is semi-auto: one trigger pull, one round. Release the trigger and it stops — unlike a binary trigger. Chris put 200 rounds thro…