Retro AR-15 builders have lived in a compromise for years. Every quality forced reset selector on the market shipped with the same modern, aggressive lever shape, textured for fast thumb manipulation but visually wrong on any rifle built to look like a 1980s or 1990s service weapon. Drop a standard Atrius lever onto an A1 with green furniture, an M16A4 clone with KAC rails, or a Colt 6920 with faux full-auto markings, and the modern selector geometry stands out from across the room. The Mil-Spec FRS fixes that.

At $199 it ties the standard Atrius FRS for the cheapest entry in the lineup and undercuts the $249 ambidextrous version by $50. The selector body uses the same heat-treated 4140 steel as the rest of the Atrius family, the same 90- degree throw, and the same three firing modes (Safe, Semi, Super-Semi). The cam-lever architecture inside is unchanged. The single difference is the lever profile itself, machined to mimic a traditional mil-spec safety with the classic ridges and pointer found on a stock AR-15 selector. From the receiver out it looks period-correct. From the buffer tube down it forces the trigger to reset between shots.

Compatibility tracks the standard Atrius FRS exactly. It drops in on any mil-spec full-profile AR-15 fire control group chambered in .223 Remington, 5.56 NATO, or .300 Blackout. It runs on Geissele triggers cut for the Atrius super safety. It does not run on a stock Geissele two-stage without that cut, which is the gap the G-Lever covers. Installation is the same swap as any other Atrius single- side, minor fitment may be required during install. MPN ADG-FRS-S-MS, UPC 850079014084, made in the USA. Ships in the same black Atrius bag as the standard single-side, so if a third-party listing arrives without the bag, return it.

For the broader picture of how the Mil-Spec slots in next to the rest of the Atrius family and the wider FRS market, the Atrius FRS review breaks the platform down end to end. The super safety guide walks through every selector-based FRS on the market with a compatibility checker.

The Atrius forced reset selector is a mechanically leveraged safety that forces the trigger to reset on its own between shots, giving the shooter a faster cyclic rate without the internal-component wear that plagues traditional forced reset triggers. The original Atrius FRS and the Atrius Ambidextrous FRS both work with mil-spec fire control groups, but Geissele compatibility was always the catch: earlier versions required a small relief notch cut into the trigger tail to clear the cam lever. That meant either dedicating a Geissele trigger to the cut, or paying extra for a Geissele super safety cut variant.

The G-Lever solves that compatibility problem with a dedicated aluminum lever blocker that limits cam travel under the Geissele hammer. SSA, SSA-E, and G2S triggers install bone-stock. For shooters who already paid $250 to $480 for a Geissele two-stage and do not want to take a file or Dremel to it, the G-Lever is the first Atrius part that respects that investment. If you are still picking a base trigger, our super safety guide and the forced reset buyer's guide walk through the full FRS and FRT landscape.

Inside any Atrius FRS, a cam lever rides against the trigger and resets it after the hammer drops. With a mil-spec hammer, the cam has plenty of clearance and the reset is predictable. Geissele two-stage hammers sit at a different angle and expose less clearance, so on the original Atrius the cam could over-rotate and bind under the hammer mid-string. Atrius' earlier workaround was to cut a relief notch in the trigger tail, which added engineering work for the user and risked bricking a $250-plus trigger if the cut was off.

The G-Lever ships with a black-nitrided aluminum block that physically caps cam rotation at the correct stop point for a Geissele two-stage. The block sits behind the selector body and references off the hammer geometry rather than the trigger tail. The result is the same Super-Semi firing behavior the standard Atrius delivers, with no metal removed from the trigger and no measurable change to first-stage or second-stage pull weights. The hammer is unmodified, the trigger is unmodified, and the rifle returns to a standard Geissele build by removing two parts.

PSR's launch-day video walks the G-Lever through seven different rifle and PCC builds, including a Geissele Super Duty 11.5, a Schmid 2-stage trigger build, a K-23B stubby with a 3-round burst limiter, a Springfield Kuna 9mm PCC, and a Daniel Defense 11.5 on an LMT lower. The takeaway: the SSA and SSA-E pair best, with the SSA-E producing the cleanest perceived reset due to its lighter second stage. Schmid 2-stage triggers also worked, with the highest cyclic rate of the test.

The video is embedded below.

On a Geissele Super Duty 11.5, the cyclic rate sits in the same range as a stock Atrius on a mil-spec FCG, but with the cleaner break that the SSA-E's tuned second stage delivers. That is the practical reason to buy this part: you keep the trigger feel you already paid for, and you get the forced reset on top of it. For a build that centers on a suppressed 11.5 with a Geissele two-stage, the G-Lever is now the obvious selector choice. Use our rifle builder to lay out the rest of the parts list, or compare platforms side-by-side if you are still choosing a host.

The forced reset selector market has stratified into a clear price ladder. The Mars 3-position FRT super safety holds the budget tier at $139 with mil-spec FCG support and no ambidextrous variant. Atrius now spans the middle and top of the ladder with four single-side and ambi variants, all of them sharing the same heat-treated 4140 steel internals.

The new Mil-Spec single-side FRS, also released this launch window, swaps the standard Atrius lever for a traditional mil-spec profile selector with the classic ridges and pointer. Same internals as the $199 standard single-side, same trigger compatibility, just a period-correct lever shape for retro A1, A2, and M16A4 clone builds where the modern Atrius lever looks out of place. If you are running a vintage Colt clone with faux full-auto markings, the Mil-Spec variant is the right pick. For everyone else, the decision is whether you need ambi controls (Ambi at $249), Geissele stock-trigger compatibility (G-Lever at $269), or the cheapest entry into the FRS category (Mars at $139).

For a closer look at the Atrius family in general, see our Atrius FRS review. If you would rather have a complete forced reset trigger than a selector swap, the Partisan Disruptor FRT review covers the high-end FRT path. And if you want to skip the Atrius cam-lever architecture entirely, the AS Designs Arc V2 uses a different mechanical approach with broader platform support.

Atrius' dual launch covers two distinct customers. The Mil-Spec FRS is for retro and clone builders who refused to put a modern aggressive lever on a period-correct receiver. At $199 it costs the same as the standard single-side and delivers identical forced reset performance, so the only question is which lever shape lives on your rifle. If your build sells the period look from the dust cover up, the Mil-Spec lever is the right answer.

The G-Lever is for Geissele two-stage owners who refused to cut a $250-plus trigger to make an Atrius work. At $269 it is a $20 premium over the standard ambi Atrius FRS for one extra machined aluminum part and the compatibility gap that had been the only meaningful reason not to buy an Atrius. If you run an SSA, SSA-E, or G2S, this is the only ambidextrous forced reset selector that drops in unmodified. Skip it on the X Series triggers, those are still incompatible.

Verify your state law before ordering either part. Forced reset selectors are unrestricted federally after the May 2025 DOJ settlement, but state-level restrictions are still active in roughly 15 states. For the rest of the build, our rifle builder and the full catalog cover compatible hosts, suppressors, and optics.