FRT-MR3™
About this product
The FRT-MR3™ is a Single-Stage (3-Position) Forced Reset Trigger engineered specifically for HK MR223 and HK MR556 platforms. This precision drop-in system maintains the HK416-style selector drum geometry while enabling controlled rapid-fire capability. The trigger operates with a consistent 4.5-pound pull weight across all functions, returning the hammer automatically upon bolt carrier group reset.
What is the FRT-MR3™ used for?
The FRT-MR3™ provides rapid-fire functionality for HK MR223/MR556 rifles while maintaining semi-automatic compliance. It achieves this through a forced reset mechanism that returns the trigger to the reset position after each shot, requiring the shooter to release and re-engage for subsequent rounds. The system maintains full third-position functionality for standard semi-auto operation.
How does the FRT-MR3™ compare to the Freedom Finger™ M&P® 2.0 Forced Reset Trigger?
The FRT-MR3™ employs HK-specific selector drum geometry, unlike the M&P-optimized Freedom Finger™ system. The MR3's 4.5-pound trigger pull is 1.2 pounds heavier than the Freedom Finger's 3.3-pound configuration, prioritizing reliability over ultimate speed. Both systems maintain the same mechanical reset principle but are platform-specific in their implementation.
What does it weigh and what are the dimensions?
The complete FRT-MR3™ assembly weighs 3.8 ounces with all included components installed. The trigger housing measures 1.38 inches wide by 2.94 inches long, with a hammer pivot pin spacing of 0.315 inches. These dimensions are critical for proper fitment in HK-pattern lower receivers requiring specific machining tolerances.
Who is this NOT for?
The FRT-MR3™ is incompatible with standard AR-15 platform rifles and requires specific HK MR223/MR556 lower receivers. Users seeking traditional binary trigger functionality should consider alternative systems, as the forced reset mechanism requires distinct firing discipline. The system demands proper installation timing protocols to avoid mechanical timing issues.
What's in the box?
The FRT-MR3™ package contains exactly six discrete components plus installation tools: 1 trigger assembly, 2 anti-walk pins, 4 anti-walk pin screws, 2 selector drums (A1 and A4 patterns), 2 selector lever roll pins, and 2 T10 Torx wrenches. This 13-piece kit provides all hardware needed for complete installation without requiring additional purchases.
Is the FRT-MR3™ worth it at $525?
At $525, the FRT-MR3™ represents premium pricing for HK-platform forced-reset capability. The investment is justified by the specialized engineering required for HK selector drum compatibility and the precision machining of all components. For MR223/MR556 owners seeking this specific functionality, the price reflects the niche manufacturing requirements and low production volume.
Specs at a glance
Video review
Pros & cons
What works
- Weighs 3.8 oz complete - 0.6 oz lighter than modified binary trigger setups
- Includes both A1 and A4 selector drums - covers all HK MR223/MR556 variants
- 4.5-pound consistent pull weight - maintains reliability across fire control group
- Complete installation kit - 13 components eliminate additional purchases
Trade-offs
- HK-platform exclusive - incompatible with standard AR-15 lowers without modification
- Requires precise timing adjustment - 5-7 minute protocol critical for function
- $525 price point - premium cost compared to AR-15 platform FRT systems
- Limited to two units per transaction - restricts bulk purchases for multiple builds
Expert review
Key attributes
| Type | Single-Stage (3-Position) Forced Reset Trigger |
| Firearm Models | HK MR223 & HK MR556 |
| Pull Weight | 4.5 pounds |
| Weight | 3.8 oz |
| Width | 1.38 inches |
| Length | 2.94 inches |
| Finish | Hardcoat Anodized |
| Includes | 13 components with installation tools |
Specifications
| type | Single-Stage (3-Position) Forced Reset Trigger |
| firearm_models | HK MR223 & HK MR556 |
What's in the box
- 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
Frequently asked questions
- Is it compatible with standard AR-15 lowers?
- No, the FRT-MR3™ is engineered exclusively for HK MR223 and HK MR556 platforms. The selector drum geometry and trigger group dimensions are specific to HK-pattern lowers. Attempted installation in standard AR-15 receivers will result in non-functional selector positions and potential damage.
- Does it require special installation tools?
- The kit includes two T10 Torx wrenches sufficient for complete installation. No additional tools are required beyond standard armorer's punches for roll pin installation. Total installation time for a qualified gunsmith averages 22 minutes following the FRT-15 Installation & Timing Protocol.
- Can I use my existing HK selector levers?
- Yes, standard HK MR223/MR556 selector levers interface correctly with the included A1 and A4 selector drums. The system maintains the original 90-degree throw angle and detent positioning. Both ambidextrous and standard lever configurations function identically to factory specifications.
- Does this work with Geissele maritime bolt catches?
- Compatibility requires verification per the <a href="/blog/frt-binary-trigger-geissele-maritime-bolt-catch-compatibility/">Geissele maritime bolt catch analysis</a>. Some lower receivers may require minor clearance modifications. The hammer geometry clears most aftermarket bolt catch designs when properly timed during installation.
- What is the return policy if it doesn't fit?
- Returns are accepted within 14 days of purchase for uninstalled components. Installation voids the return eligibility due to wear patterns. FRT Triggers provides technical support for fitment issues, with most resolution occurring through proper timing adjustment rather than component replacement.