AS Designs ARC-Fire Review: 400 Rounds on the SIG MCX Spear LT

The ARC-Fire was tested on a SIG MCX Spear LT 11.5" in 5.56 NATO with the AS Designs MCX Slip Trip Kit. The trigger is a Geissele SSA-E, a two-stage with a 3.5 lb total pull and crisp break. Suppressor is a HUXWRX Flow 556K, which stayed on for all 400 rounds of M193.

This is a piston-driven platform, not direct impingement. Most ARC-Fire reviews are on standard AR-15s, so the MCX compatibility data here fills a gap. For our full take on the Spear LT itself, see the SIG Spear LT 1,000-round review.

The ARC-Fire is a forced reset selector (FRS), not a forced reset trigger (FRT). The distinction matters. An FRT like the Partisan Disruptor replaces your entire fire control group. Whatever trigger feel that unit ships with is what you get. The Disruptor's semi-auto break is gritty, worse than milspec. That is the trade-off.

An FRS replaces only your safety selector. Your hammer, trigger, disconnector, and springs stay in the gun. The ARC-Fire's cam and lever mechanism forces the trigger reset through the selector system rather than through the trigger itself. The result: you keep your Geissele SSA-E for semi-auto work and flip to ARC mode when you want forced reset. Best of both worlds.

For a full breakdown of how forced reset systems work, selector compatibility, and a rate-of-fire calculator, see our Super Safety and FRT Guide.

Installation was not terrible, but it was not straightforward either. The ARC-Fire kit includes the ARC cam, lever, detent bar, primary selector, ambi selector, a pre-cut trigger, and a standard safety detent. For the MCX, you also need the MCX Slip Trip Kit.

One thing worth noting: AS Designs support was responsive and helpful throughout the install process, and this was before they knew we were reviewers. We reached out as a regular customer and got prompt, knowledgeable answers. That matters when you are dealing with a product that may require troubleshooting on non-standard platforms.

The first install resulted in the safety getting stuck in whatever position it was set to. The selector would not rotate. Removing the entire assembly and reinstalling it from scratch fixed the issue. The binding appears to come from how the cam and lever seat in the lower, and it needs to be aligned precisely on the first try.

Beyond the MCX-specific issue, the general installation considerations match what AS Designs documents:

• →Anti-walk pins: AS Designs recommends them, but we ran 400 rounds without anti-walk pins and had no pin migration. Add them if you notice pins walking during use.
• →Expect to reinstall at least once. The cam alignment is finicky. If the safety binds or the selector will not rotate, pull it and start over rather than forcing it.
• →Compared to the Partisan Disruptor: The Disruptor is a cassette drop-in that takes five minutes with a torx wrench. The ARC-Fire requires more mechanical sympathy. If you want the easiest possible install, the Partisan is the better choice.

The ARC-Fire's biggest weakness is the safety selector itself. It binds during rotation. It does not have a true 45-degree throw. It does not have the positive, tactile detent that shooters expect from quality selectors like the Radian Talon.

The throw from Safe to Semi feels acceptable. The throw from Semi to ARC is where the problems show up. There is noticeable resistance and a gritty, imprecise feel as the selector moves through the full 180-degree arc to reach ARC mode. After a Radian Talon, which snaps into position with zero ambiguity, the ARC-Fire selector feels like a parts-bin solution.

This is functional, not broken. You can manipulate it under stress and it does land in the right position. But for a $250 product on a $2,500+ rifle, the selector feel is below expectations. AS Designs clearly prioritized the ARC mechanism itself over selector ergonomics, and it shows.

After removing the MCX firing pin safety latch, the ARC-Fire has been flawless in ARC mode through 400 rounds of M193, all suppressed with the HUXWRX Flow 556K. Zero failures to reset, zero light primer strikes, zero cycling issues.

One hammer follow occurred in semi-auto mode. The hammer dropped without a trigger press during normal semi-auto firing. This appears to be a Geissele-in-MCX issue rather than an ARC-Fire problem. The Spear LT's piston system cycles with different timing than a DI gun, and the SSA-E's lighter engagement surfaces may be marginal in this configuration under certain conditions. It has not recurred.

The ARC mode itself feels good. The reset is positive without the grinding sensation that some users report with first-generation forced reset systems. The patent-pending Active Reset Clutch mechanism delivers a noticeably smoother forced reset cycle than older designs.

Having run all three systems, here is how they compare. Each makes different trade-offs, and the right choice depends on what you prioritize.

The ARC-Fire's biggest advantage is clear: you keep your existing trigger for semi-auto work. If you have a Geissele SSA-E, you get a crisp 3.5 lb two-stage break in semi and ARC mode when you want rapid fire. The Partisan Disruptor forces you into its included trigger, which is noticeably worse than milspec for precision shooting.

The Partisan wins on installation simplicity. Five minutes, one torx wrench, no fitting required. The ARC-Fire demands more patience and mechanical aptitude, especially on non-AR platforms.

Platform support is where the ARC-Fire has no competition. If you run an MCX, MP5, SCAR, or any other supported platform, the ARC-Fire is your only option for forced reset functionality. The Partisan and Rare Breed are AR-15 only.

AS Designs unveiled the ARC-Fire V2 at SHOT Show 2026 with a March 2026 release target. The V2 addresses the two biggest complaints about the V1: selector throw and drag.

• →Selector throw options: 45-to-90, B&T 180-degree, and HK-style three-position configurations
• →Reduced system drag: Smoother ARC cycling with less of the grinding feel some users report
• →Expanded platform support: Additional HK and B&T compatibility

Forced reset selectors are federally legal following the May 2025 DOJ settlement acknowledging they are not classified as machine guns under the National Firearms Act.