FRT-MR3™
About this product
The FRT-MR3™ is a Single-Stage (3-Position) Forced Reset Trigger engineered specifically for the HK MR223 and HK MR556 platforms, designed to achieve a distinct, high-performance firing cycle. This kit provides the core components to convert your standard trigger group into a specialized assembly, packaged with all necessary installation hardware. It follows the same logic as our complete build kits—focusing on mechanical precision and saving the serious builder significant research and parts-sourcing time.
What is the FRT-MR3™ used for?
This trigger assembly is used to create a forced reset action, which initiates the next shot's trigger pull cycle immediately upon the bolt carrier's forward movement rather than on release of the trigger. This mechanical process yields a distinctive firing characteristic separate from a standard semi-automatic trigger. It is intended for dedicated use on compatible, centerfire HK-style rifles where function and mechanical durability are the primary objectives over standard pull weight tuning.
How does the FRT-MR3™ compare to a standard HK trigger pack?
The FRT-MR3™ is engineered for a fundamentally different firing action than a standard HK MR556 trigger pack. Where a standard pack offers a two-stage pull with a 8-9 lb. total weight, the FRT-MR3™ is a single-stage forced reset mechanism offering a distinct 3-position cycle with a 4.5 lb. pull. The FRT-MR3™ is better for achieving its specific mechanical action, while a standard pack is better for predictable, traditional semi-automatic fire.
What does it weigh and what are the dimensions?
The trigger assembly itself weighs 4.2 ounces and has a profile of 1.3 inches in width and 3.8 inches in length to fit standard HK fire control group pocket dimensions. Combined with all included pins, wrenches, and selector components, the shipping weight of the complete kit is 6.9 ounces. Its design maintains the standard 0.169-inch trigger and hammer pin hole spacing required for drop-in compatibility.
Who is this NOT for?
This kit is not for builders seeking a traditional two-stage match trigger or those building a platform for general-purpose defensive use. It is also not mechanically compatible with standard AR-15 pattern rifles, including the .308 80% Lower – Billet, due to differences in hammer geometry and safety selector configuration. For a more conventional trigger for an LR-308 build, our Polymer80 LR-308 80% Lower Receiver page details compatibility with common AR-10 fire control groups.
What's in the box?
The kit includes one complete FRT-MR3™ trigger unit, two anti-walk pins with four securing screws, two selector lever drums (A1 and A4 styles), two selector lever roll pins, and two T10 Torx wrenches. This inventory covers all hardware needed for installation without requiring additional parts, a logistical advantage detailed similarly in our Community Build Showcase for complete DIY projects.
Is the FRT-MR3™ worth it at $525?
At $525, this kit is worth it for the builder who specifically requires a forced reset mechanism for their HK MR223/MR556 and values the guarantee of all compatible hardware in one verified kit. The price reflects the specialized machining, low-volume production, and complete accessory bundle that eliminates guesswork. It is not a cost-effective upgrade for someone merely seeking a lighter traditional trigger pull.
Specs at a glance
Video review
Pros & cons
What works
- Complete kit includes all specialized hardware (2 drums, pins, T10 wrenches).
- 4.2 oz trigger weight maintains balanced lower receiver handling.
- Single-stage 4.5 lb. pull weight optimized for the forced reset mechanism.
- Factory-installed anti-walk pins eliminate a common post-build failure point.
Trade-offs
- Zero compatibility with common AR-15 or AR-10 lowers limits platform versatility.
- High $525 price point for a single fire control component.
- Installation requires familiarity with HK platform-specific disassembly (roughly 25 minutes for a novice).
- Specialized function offers no benefit for traditional semi-automatic shooting.
Expert review
Key attributes
| Type | Single-Stage Forced Reset Trigger |
| Compatibility | HK MR223, HK MR556 |
| Pull Weight | 4.5 lb. |
| Positions | 3 (Safe, Semi, Reset) |
| Trigger Weight | 4.2 oz |
| Finish | Phosphate & Hard Coat |
| Includes Wrenches | 2x T10 Torx |
| Max Per Order | 2 units |
Specifications
| type | Single-Stage (3-Position) Forced Reset Trigger |
| compatibility | HK MR223 & HK MR556 |
| max_per_transaction | 2 triggers |
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 a standard AR-15 lower receiver?
- No, the FRT-MR3™ is not compatible with standard AR-15 or AR-10 pattern lower receivers, which includes our .308 80% Lower. It is designed exclusively for the HK MR223 and HK MR556 platforms due to specific hammer geometry and the 3-position selector drum system.
- Does it fit the HK MR762 or HK417?
- No, this trigger is not designed for the .308 HK MR762/HK417 platform. The hammer hook geometry and fire control pocket dimensions differ, preventing a safe or functional fit. It is only for the 5.56mm MR223 and MR556 rifles.
- How long does shipping take?
- For this component, standard processing and shipping typically adds 3-5 business days to your order timeline. For detailed information on bulk or multiple-item orders, refer to our dedicated article, <a href="/blog/arcforge-arms-bulk-order-lead-times/">ArcForge Arms Bulk Order Lead Times</a>.
- Can I return it if it doesn't fit my build?
- Returns are accepted within 30 days for uninstalled, undamaged components. Once any part of the trigger group has been installed or modified, the item is not eligible for return. Full details are available in our <a href="/blog/arcforge-arms-component-return-policy/">Component Return Policy</a>.
- Does this work with a Geissele HK SMR handguard installed?
- Yes, as the trigger group is internal to the lower receiver, it is fully compatible with all aftermarket handguards, including the Geissele HK SMR series. No interference is present.