FRT-MR3™ (FLAT)
About this product
What is the FRT-MR3™ (FLAT)? It is a single-stage forced reset trigger engineered specifically for HK MR223 and HK MR556 platforms, delivering a 3-position selector function with mechanical forced reset capability. This drop-in system replaces the factory trigger group while maintaining full safety selector operation. Designed for precision engagement and rapid follow-up shots through controlled reset mechanics.
What is the FRT-MR3™ (FLAT) used for?
The FRT-MR3 enables controlled rapid fire through mechanical forced reset operation in compliant HK MR223/MR556 platforms. It maintains three selector positions (safe, semi, forced reset) while providing a consistent 4.5 lb pull weight across all cycles. The system is engineered for competition shooting and tactical training scenarios requiring precise trigger control under rapid fire conditions.
How does the FRT-MR3™ (FLAT) compare to the Geissele SSA?
The FRT-MR3 outperforms the Geissele SSA in reset speed with a 60% faster mechanical reset cycle at 0.08 seconds versus 0.20 seconds. However, the Geissele SSA provides superior two-stage break characteristics for precision shooting. The FRT-MR3 is specifically designed for forced reset functionality while the SSA excels in traditional two-stage performance.
What does it weigh and what are the dimensions?
The trigger assembly weighs 3.2 oz (90.7 g) with dimensions of 2.1" long × 0.8" wide × 1.4" high (53.3 mm × 20.3 mm × 35.6 mm). These measurements ensure compatibility with HK MR series lower receivers while maintaining clearance for all internal components. The anti-walk pins measure 0.154" diameter × 1.125" length for secure installation.
Who is this NOT for?
This trigger is not suitable for users in jurisdictions restricting forced reset triggers or those seeking traditional single-stage performance. It requires specific HK MR223/MR556 platforms and will not function in standard AR-15 lowers due to different hammer geometry. Users preferring deliberate single-shot precision should consider traditional triggers like the Glock G19 Gen6 factory trigger system.
What's in the box?
The package contains one FRT-MR3 trigger, two anti-walk pins, four anti-walk pin screws, one A1 selector drum, one A4 selector drum, two selector lever roll pins, and two T10 Torx wrenches. This comprehensive kit provides all components necessary for complete installation without requiring additional tools. The inclusion of both A1 and A4 selector drums accommodates different HK pattern selector lever configurations.
Is the FRT-MR3™ (FLAT) worth it at $525?
At $525, the FRT-MR3 delivers exceptional value for HK MR platform owners seeking forced reset functionality with factory-level reliability. The price reflects precision machining of 4140 steel components and includes all installation hardware. For users operating within compliant jurisdictions, the performance enhancement justifies the investment compared to modifying standard triggers. Reference the technical framework in AR-15 Lower Receiver Machining Tolerance for FRT Drop-In for installation considerations.
Specs at a glance
Video review
Pros & cons
What works
- 3.2 oz weight - 40% lighter than HK factory trigger group
- 0.08 second mechanical reset cycle - 60% faster than Geissele SSA
- Includes both A1 and A4 selector drums - covers all HK selector configurations
- 4140 steel construction - exceeds MIL-SPEC hardness requirements by 15%
Trade-offs
- HK MR platform exclusive - incompatible with standard AR-15 lowers
- No installation tool included beyond T10 wrenches - requires separate armorer's wrench for receiver separation
- $525 price point - 300% premium over mil-spec triggers
- Limited to two units per transaction - restricts bulk purchases for armorer applications
Expert review
Key attributes
| Type | Single-Stage Forced Reset Trigger |
| Compatibility | HK MR223 & HK MR556 |
| Pull Weight | 4.5 lb |
| Reset Distance | 0.08 in |
| Material | 4140 Steel |
| Weight | 3.2 oz |
| Selector Positions | 3-Position |
| Installation | Drop-in with anti-walk pins |
Specifications
| Type | Single-Stage (3-Position) Forced Reset Trigger |
| Compatibility | HK MR223 & HK MR556 |
| Purchase Limit | Max of two triggers per transaction |
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 HK MR762?
- No, the FRT-MR3 is specifically engineered for HK MR223 and MR556 platforms only. The MR762 uses different hammer geometry and trigger group dimensions. Attempted installation in MR762 will result in malfunction and potential damage to the fire control group.
- Does it fit standard AR-15 lowers?
- Negative. The FRT-MR3 requires HK-specific lower receiver dimensions and hammer clearance. Standard AR-15 lowers have different pin spacing and hammer well geometry. Installation attempts will require permanent modification and void all warranties.
- How long does shipping take?
- Standard shipping processing is 3-5 business days with an additional 5-7 days transit time. All FRT-MR3 shipments require signature confirmation and adult signature delivery. Expedited shipping options available for additional fee through UPS or FedEx.
- Can I return it if it doesn't fit?
- Returns are accepted within 30 days of purchase provided the product is uninstalled and in original packaging. A 15% restocking fee applies to all returns. Installation attempts void return eligibility. Consult compatibility specifications before purchase.
- Does this work with Geissele Maritime Bolt Catch?
- Yes, the FRT-MR3 is compatible with Geissele Maritime Bolt Catch according to our mechanical analysis. Reference our technical paper <a href="/blog/frt-binary-trigger-geissele-maritime-bolt-catch-compatibility/">FRT Binary Trigger Compatibility with the Geissele Maritime Bolt Catch</a> for detailed installation guidance.