FRT MR3 Single Stage 3 Position Forced Reset Trigger For The HK MR223 HK MR556

About this product

The FRT-MR3 is a drop-in, duty-grade forced reset trigger built specifically for the HK MR223 and HK MR556 platforms, made from 7075 anodized aluminum and heat-treated 4140 and S7 steel. Unlike AR-15 forced reset triggers, the FRT-MR3 is engineered to interface with the factory semi-automatic bolt carrier group HK uses on these rifles, and it is not compatible with HK416 or BRN4 full-auto bolt carrier groups.

What does the FRT-MR3's 3-position selector do?

The trigger uses an ambidextrous 3-position safety selector offering Safe, Semi, and Forced Reset modes. In Semi it functions as a standard trigger. In Forced Reset mode, the trigger mechanically resets forward after each shot and is held there until the bolt carrier group returns to battery, producing a short, repeatable reset distance for faster follow-up shots. Every mode fires exactly one round per trigger pull — the mechanism changes reset speed, not rounds fired per pull.

What's included, and how heavy is the unit?

The complete kit includes the FRT-MR3 trigger, two anti-walk pins with four mounting screws, an A1 selector drum, an A4 selector drum, two selector lever roll pins, and two T10 Torx wrenches for installation. The assembled trigger unit weighs 5 ounces, and it's built entirely in the USA.

Does this need to ship through an FFL?

No. A trigger is a part, not a firearm, so the FRT-MR3 ships directly to your address without an FFL transfer. That said, forced reset triggers have faced ongoing regulatory scrutiny and shifting legal positions at the federal level over the past several years. Confirm the current legal status of forced reset triggers under federal law and in your state before ordering, since this is an actively evolving area of firearms regulation.

Will it fit any HK-pattern rifle?

No — this specific model is engineered for the HK MR223 and HK MR556 platforms using their factory semi-auto bolt carrier groups. It is explicitly not compatible with HK416 or BRN4 full-auto BCGs, so confirm your exact rifle model and bolt carrier group before ordering, since fitment on HK-pattern rifles is more model-specific than on standard AR-15 lowers.

For MR223/MR556 owners specifically, aftermarket trigger options tend to be more limited than for standard AR-15 lowers because of the platform's tighter tolerances and HK-specific fire control geometry, which is part of why a purpose-built option like the FRT-MR3 commands a premium over typical AR-15 forced reset triggers. Installation still requires care and the correct tools, and shooters unfamiliar with HK-pattern trigger groups may want a qualified gunsmith to handle the swap.

HK's MR223 and MR556 rifles are semi-automatic civilian variants built to the same general lineage as HK's select-fire military rifles, and owners of these platforms tend to be experienced shooters already invested in a premium rifle purchase, which is part of why a specialized trigger upgrade at this price point has a ready market. The reset behavior in FRT mode is mechanically similar in concept to AR-15 forced reset triggers, but the specific geometry, spring rates, and interface with HK's fire control components are unique to this product — a generic AR-15 FRT will not fit or function safely in an MR223/MR556 lower without the modifications this trigger is purpose-built to provide. Given the investment already made in an HK-pattern rifle, pairing it with a trigger built specifically for that platform, rather than adapting a generic AR-15 part, is the more reliable path for owners who want this specific feature.