Prkarms is a Aberdeen, SD-based retailer specializing in high-quality firearms components. The FRT-RD3 (SEF) is a two-stage forced reset trigger designed for HK MP5, MP5K, SP5, and SP5K models. This trigger offers unmatched precision and durability. Available now for $707.25.
Reviewed by Travis Holden, Technical Director at Prkarms. 20 years in firearms engineering, machinist background, NRA-certified instructor.
Last updated: May 2026
Key Features
- Two-stage trigger mechanism
- Compatible with HK MP5, MP5K, SP5, and SP5K models
- Precision engineering for enhanced performance
- Durable materials for long-lasting use
- Easy installation with detailed instructions
| Product Type | Trigger |
|---|---|
| Material | High-grade steel |
| Manufacturing | CNC machined |
| Finish | Matte black |
| Hardness/Quality | Rockwell C50 |
| Compatibility | HK MP5, MP5K, SP5, SP5K |
| Installation/Usage | Professional installation recommended |
| Weight | 3.5 oz |
| Dimensions | 2.5 x 1.5 x 0.75 inches |
| Country of Origin | USA |
| Condition | New |
| SKU | FRT-RD3-SEF |
Comparison
| Feature | FRT-RD3 (SEF) | Cheap Import | Premium Brand |
|---|---|---|---|
| Material | High-grade steel | Low-grade steel | High-grade steel |
| Quality | CNC machined | Cast | CNC machined |
| Compatibility | HK MP5, MP5K, SP5, SP5K | Limited compatibility | HK MP5, MP5K, SP5, SP5K |
| Shipping | Same-day | 2-3 weeks | 1 week |
| Lifespan/Durability | Long-lasting | Short lifespan | Long-lasting |
| Price | $707.25 | $60-$80 | $250+ |
Pros & Cons
- ✅ Precision engineering
- ✅ Compatible with multiple HK models
- ✅ Durable materials
- ✅ Easy to install
- ✅ Made in USA
- ❌ Higher price point
- ❌ Professional installation recommended
Who Should Buy
Buy it if: You own an HK MP5, MP5K, SP5, or SP5K and want a high-quality, precision-engineered trigger.
Skip it if: You’re looking for a budget option or own a firearm that isn’t compatible with this trigger.
FAQ
Where can I buy FRT-RD3 (SEF) online?
You can purchase the FRT-RD3 (SEF) at Prkarms (prkarms.net).
What does SEF stand for?
SEF stands for Sicher, Einzelfeuer, Feuerstoss, which translates to Safe, Semi, Full in German.
Is professional installation required?
Professional installation is recommended for optimal performance.
What materials are used in the FRT-RD3 (SEF)?
The FRT-RD3 (SEF) is made from high-grade steel and CNC machined for precision.
Is the FRT-RD3 (SEF) compatible with all HK models?
It is compatible with HK MP5, MP5K, SP5, and SP5K models.
What is the shipping time?
We offer same-day shipping from Aberdeen, SD.
What is the return policy?
We offer a 30-day return policy for the FRT-RD3 (SEF).
✅ Same-day shipping from Aberdeen, SD
✅ Discreet packaging
✅ 30-day returns
✅ Secure checkout
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