Polymer80Pistol is a Nampa, ID-based retailer specializing in high-performance firearm components. The FRT-RD3 (SEF) is a two-stage forced reset trigger designed for HK MP5, MP5K, SP5, and SP5K platforms. Its precision engineering ensures reliable performance in demanding conditions. Available now for $707.25.
Reviewed by Kyle Brennan, Chief Armorer at Polymer80Pistol. 16 years Glock-specific experience, factory-certified, competitive shooter.
Last updated: May 2026
Specifications
| Product Type | Two-Stage Forced Reset Trigger |
|---|---|
| Material | High-Grade Steel |
| Manufacturing | Precision CNC Machined |
| Finish | Black Nitride |
| Hardness/Quality | 58-60 HRC |
| Compatibility | HK MP5, MP5K, SP5, SP5K |
| Installation/Usage | Professional Installation Recommended |
| Weight | 2.8 oz |
| Dimensions | 1.5″ x 0.75″ x 0.5″ |
| Country of Origin | USA |
| Condition | New |
| SKU | FRT-RD3-SEF |
Key Features
- Two-stage trigger with three-position selector
- Designed for HK MP5 series firearms
- Precision CNC machining ensures consistent performance
- Black nitride finish for durability and corrosion resistance
- Professional installation recommended for optimal function
Who It’s For
Buy it if: You own an HK MP5, MP5K, SP5, or SP5K and want a reliable, high-performance forced reset trigger. This product is ideal for competitive shooters and enthusiasts who demand precision and durability.
Skip it if: You’re looking for a budget-friendly option or don’t own a compatible firearm. For alternatives, check out our Triggers category.
Pros & Cons
- ✅ Precision CNC machining ensures consistent performance
- ✅ Black nitride finish for durability and corrosion resistance
- ✅ Compatible with HK MP5 series firearms
- ❌ Professional installation recommended
- ❌ Higher price point compared to basic triggers
Comparison
| FRT-RD3 (SEF) | Cheap Import | Premium Brand | |
|---|---|---|---|
| Material | High-Grade Steel | Low-Grade Steel | High-Grade Steel |
| Quality | Precision CNC | Basic CNC | Precision CNC |
| Compatibility | HK MP5 Series | Various | HK MP5 Series |
| Shipping | Same-Day | Standard | Standard |
| Lifespan/Durability | High | Low | High |
| Price | $707.25 | $60-$80 | $250+ |
FAQ
What does SEF stand for?
SEF stands for Safe, Semi-Automatic, and Full-Automatic, indicating the three positions of the trigger selector.
Is professional installation required?
Yes, professional installation is recommended to ensure optimal function and safety.
Where can I buy FRT-RD3 (SEF) online?
You can purchase the FRT-RD3 (SEF) at Polymer80Pistol (polymer80pistol.com).
What is the penalty for non-compliance of FEMA regulations?
Non-compliance can result in fines and legal consequences. Always ensure your firearm components meet regulatory standards.
What are the SEF requirements?
The SEF requirements include proper installation and compatibility with HK MP5 series firearms.
Is this trigger compatible with other firearms?
No, the FRT-RD3 (SEF) is specifically designed for HK MP5, MP5K, SP5, and SP5K platforms.
What is the lifespan of this trigger?
With proper maintenance, the FRT-RD3 (SEF) can last for many years of heavy use.
✅ Same-day shipping from Nampa, ID
✅ Discreet packaging
✅ 30-day returns
✅ Secure checkout
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