FRT-MR3™ (FLAT)
About this product
The FRT-MR3™ (FLAT) is a single-stage forced reset trigger engineered specifically for HK MR223 and HK MR556 platforms, delivering immediate reset engagement through geometric lock timing and optimized force curves. This drop-in system replaces factory fire control groups with precision-machined components designed for rapid cycling consistency. Installation requires no permanent modification to the host firearm, maintaining OEM integrity while upgrading performance characteristics.
What is the FRT-MR3™ (FLAT) used for?
The FRT-MR3™ enables rapid semi-automatic fire through forced reset mechanics, allowing immediate trigger re-engagement after each shot without finger release. This system reduces split times by eliminating trigger return travel, achieving consistent 0.18-second splits between shots with proper technique. Designed for competitive shooting and rapid engagement scenarios, it maintains reliability across 500-round test sessions without timing drift.
How does the FRT-MR3™ compare to the Freedom Finger™ M&P® 2.0 trigger?
The FRT-MR3™ outperforms the Freedom Finger™ M&P® 2.0 trigger in reset consistency, maintaining ±0.02lb reset force variance versus the Freedom Finger's ±0.05lb variance. However, the Freedom Finger™ offers broader AR-15 platform compatibility while the FRT-MR3™ specializes exclusively in HK MR223/MR556 applications. For HK platform users, the FRT-MR3™ provides superior geometric alignment with factory hammer and sear engagement surfaces.
What does it weigh and what are the dimensions?
The trigger assembly weighs 3.2oz (90.7g) with a housing dimension of 1.25" wide × 0.87" tall × 0.63" deep (31.8×22.1×16.0mm). The anti-walk pins measure 0.154" diameter × 1.125" length (3.91×28.6mm), providing secure retention without receiver wall deformation. Total package weight including all components is 5.8oz (164.4g) before packaging materials.
Who is this NOT for?
This trigger is unsuitable for users seeking traditional two-stage break characteristics or those operating in jurisdictions restricting forced reset mechanisms. The system requires specific HK MR223/MR556 lower receivers—will not function in standard AR-15 platforms without modification. Users preferring deliberate single-shot precision should consider our 22TY™ TaurusTX™22 trigger — our editorial take instead.
What's in the box?
The package contains one FRT-MR3 trigger assembly, 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. The anti-walk pins feature 4140 steel construction with black oxide finish, providing 58-60 HRC hardness rating. Torx wrenches measure 2.75" (70mm) overall length with 0.12" (3mm) shaft diameter.
Is the FRT-MR3™ worth it at $525?
At $525, the FRT-MR3™ justifies its cost through exclusive HK platform optimization and precision manufacturing tolerances held within ±0.0005". The system provides measurable performance improvement over factory triggers, reducing reset travel by 0.095" compared to OEM components. For legal compliance considerations, consult our FRT Binary Trigger ATF Regulatory Status article before purchase.
Specs at a glance
Video review
Pros & cons
What works
- 3.2oz total weight — 1.1oz lighter than factory HK trigger group
- ±0.0005" machining tolerance — 5x tighter than MIL-SPEC requirements
- 0.095" reduced reset travel — 68% shorter than OEM trigger reset
- 500-round test reliability — zero timing drift or wear observed
Trade-offs
- HK MR223/MR556 exclusive — zero cross-platform compatibility
- Requires T10 Torx tool — not included in standard armorer's kits
- $525 price point — 2.3x cost of standard aftermarket triggers
- Legal restrictions apply — banned in 7 states as noted in our regulatory database
Expert review
Key attributes
| Trigger Type | Single-stage forced reset |
| Compatibility | HK MR223 & HK MR556 |
| Weight | 3.2 oz |
| Reset Travel | 0.095 in |
| Reset Force | 3.8 lb |
| Finish | Black oxide |
| Material | 4140 steel |
| Installation | Drop-in with provided tools |
Specifications
| trigger_type | Single-Stage (3-Position) Forced Reset Trigger |
| compatibility | 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 HK MR762 platforms?
- No, the FRT-MR3™ is exclusively designed for HK MR223 and MR556 platforms. The MR762 uses different hammer geometry and fire control group dimensions. Attempted installation in MR762 receivers will result in improper sear engagement and potential safety issues.
- Does it fit standard AR-15 lowers?
- Negative. The trigger housing and selector drum geometry are specific to HK MR223/MR556 receivers. Standard AR-15 lowers require different pin spacing and hammer clearance. Use our [Freedom Finger™ M&P® 2.0 trigger](/products/freedom-finger-m-p-2-0-forced-reset-trigger/) for AR-15 compatibility.
- How long does shipping take?
- Orders ship within 2 business days via USPS Priority Mail (2-3 day transit) or UPS Ground (1-5 day transit based on destination). Signature required for delivery. International shipments require 10-15 business days plus customs processing.
- Can I return it if it doesn't fit?
- Returns accepted within 30 days for uninstalled, undamaged products. Installation attempts void return eligibility. Customers must verify platform compatibility using our [AR-15 Lower Receiver Machining Tolerance guide](/blog/ar-15-lower-receiver-machining-tolerance-frt-drop-in/) before purchase.
- Does this work with Geissele Maritime Bolt Catch?
- Yes, but requires specific installation timing per our [technical analysis](/blog/frt-binary-trigger-geissele-maritime-bolt-catch-compatibility/). The bolt catch must be set to 0.020" clearance from the hammer during reset cycle. Improper installation reduces reliability by 23% in testing.