FRT-MR3™ Forced Reset Trigger for the HK MR223 & HK MR556

$499.00

Contents:

1 x FRT-MR3 Trigger
2 x Anti-Walk Pins
4 x Anti-Walk Pin Screws
1 x A1 Selector Drum
1 x A4 Selector Drum
2 x Selector Lever Roll Pins
2 x T10 Torx Wrenches

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Now Available!

Legal To Own And Purchase!

Prices are discounted until the end of: 11th August 2026

SKU: N/A Category: Rare Breed FRT Triggers

The FRT-MR3 is Rare Breed Triggers’ 3-position forced reset trigger purpose-built for the HK MR223 and HK MR556. As part of the full Rare Breed FRT range, it resets after every shot for fast, controlled follow-up shots while firing one round per trigger pull, and it is engineered to run on the HK MR platform’s own factory hardware.

Legality: one round per trigger pull. After the May 2025 DOJ settlement, forced reset triggers of this type are not classified as machine guns under federal law. State and local laws vary, so check yours before purchase. You must be of legal age and eligible under federal, state, and local law to purchase.

The FRT-MR3 operates with the factory semi-automatic bolt carrier group of the MR223 and MR556, so it fits those uppers using the original, factory-supplied semi-auto BCG, and we recommend retaining your factory buffer and recoil spring. As one of the most platform-specific forced reset triggers we build, it is worth noting it is not compatible with HK416 or BRN4 full-auto bolt carrier groups.

Specifications and fitment

Spec	Detail
Platform	HK MR223 & HK MR556
Selector	3-position ambidextrous (Safe / Semi / Forced Reset)
Bolt carrier group	Factory semi-auto BCG of the MR223/MR556
Not compatible with	HK416 or BRN4 full-auto BCGs
Buffer / spring	Retain factory buffer & recoil spring
Materials	7075 anodized aluminum; heat-treated 4140 & S7 steel
Trigger shoe	Curved or flat
Manufacturer	Rare Breed Triggers

3-position control, duty-grade build

A 3-position ambidextrous safety selector covers Safe, Semi and Forced Reset for left- and right-handed shooters, and anti-walk pins lock the trigger group securely in place. The MR3 is machined from 7075 anodized aluminum with heat-treated 4140 and S7 steel internals for long-term durability. Choose a curved or flat trigger shoe.

Frequently asked questions

Does it need a special bolt carrier? No. It runs on the factory semi-auto BCG of the MR223/MR556 and is not compatible with HK416 or BRN4 full-auto carriers.

What about the MP5 or SP5? Those roller-delayed HKs use a different trigger; for them, see the FRT-RD3 instead.

Do I change the buffer? No. Retain the factory buffer and recoil spring for best reliability.

Is it legal? Federally legal after the 2025 DOJ settlement; confirm your state law.

Ready to upgrade your HK MR? Add the FRT-MR3 to your cart above.