3-Position SEF Selector for the FRT-RD3™ (SEF) – For use with the PTR MP5 Clone
About this product
The 3-Position SEF Selector for the FRT-RD3™ is a single-sided safety selector engineered to provide Safe, Semi-Auto, and Full-Auto function compatibility between the FRT-RD3 forced reset trigger system and the PTR MP5 clone receiver. This component resolves a known geometric incompatibility inherent to standard MP5 selector designs when interfacing with the RD3's specific actuation geometry. Proper installation establishes correct trigger pack timing and prevents engagement faults during high-cycle fire.
What is the 3-Position SEF Selector for the FRT-RD3™ used for?
This selector is used to install or retrofit the FRT-RD3™ (SEF) forced reset trigger system into a PTR MP5 clone platform. It directly replaces the factory selector lever to ensure the RD3's proprietary cam profile correctly interfaces with the receiver's 3-position detent path. Without this component, the RD3 system will experience timing malfunctions, including failure to reset or inability to achieve all selector positions, as detailed in our technical framework on AR-15 Lower Receiver Machining Tolerance for FRT Drop-In.
How does the 3-Position SEF Selector compare to the HKParts SEF Selector?
The FRT Triggers selector provides a proprietary internal cam geometry optimized for the RD3 trigger pack, while the widely available HKParts SEF selector is dimensioned for standard HK-style trigger packs. The critical difference is the cam lobe profile; the FRT version has a lobe radius of 5.8mm with a 32-degree engagement angle, precisely calculated to actuate the RD3's sear, whereas the HKParts cam is designed for a different sear geometry. For RD3 systems, the FRT Triggers selector is mechanically superior and essential for reliable function.
What does it weigh and what are the dimensions?
The selector lever weighs 22.5 grams and measures 38.1mm in length from pivot center to tip, with a shaft diameter of 6.0mm. The integrated cam lobe has a maximum radial dimension of 11.5mm from the pivot center. These dimensions ensure a precise fit within the MP5 receiver's selector channel, which has a nominal width of 6.1mm, allowing for a 0.1mm operational clearance to prevent binding.
Who is this NOT for?
This component is not for users with standard, unmodified HK or PTR MP5 trigger packs. It is also incompatible with binary trigger systems, the 22TY™ for TaurusTX™22, or other platforms. Owners of MP5 clones not using the specific FRT-RD3™ (SEF) trigger system should use their factory selector or a standard aftermarket replacement, as this selector's geometry will not interface correctly with standard sear mechanisms.
What's in the box?
The package contains one 3-Position SEF Selector, one 1/16". Allen key, and one 3/32". Allen key. No additional hardware, loctite, or detent springs are included, as installation utilizes the existing receiver components. The provided tools are sufficient for the complete installation procedure, which typically requires 15-20 minutes following proper protocol.
Is the 3-Position SEF Selector worth it at $0.00?
At the listed price, it represents a mandatory component for enabling RD3 function in the MP5 platform, not an upgrade. Its value is binary: without it, the $425+ RD3 system is non-functional in a PTR MP5. Therefore, the cost is effectively part of the total system investment for this specific configuration, a consideration similar to the compatibility assessments in our article on the FRT Binary Trigger Compatibility with the Geissele Maritime Bolt Catch.
Specs at a glance
Video review
Pros & cons
What works
- Eliminates RD3/MP5 compatibility issue - enables full 3-position function
- Weighs 22.5g with hardened 4140 steel construction - exceeds OEM material spec
- Includes correct 1/16" and 3/32" Allen keys - tools required for installation
- Precision cam lobe with 5.8mm radius - ensures correct RD3 sear timing
Trade-offs
- Single-sided operation only - no ambidextrous configuration available
- Zero-degree positive stop detent - provides less tactile feedback than a 90-degree HK-style detent
- Matte black finish only - no phosphate or nickel options for corrosion resistance matching HK spec
Expert review
Key attributes
| Type | Single-Sided Safety Selector |
| Positions | 3-Position (Safe, Semi, Full-Auto) |
| Compatibility | FRT-RD3™ (SEF), PTR 9CT/9KT MP5 Clone |
| Material | Hardened 4140 Steel |
| Finish | Matte Black Oxide |
| Weight | 22.5 g |
| Shaft Diameter | 6.0 mm |
| Included Tools | 1/16" Allen Key, 3/32" Allen Key |
Specifications
| Type | Single-Sided Safety Selector |
| Positions | 3-Position (SEF) |
| Compatibility | FRT-RD3™ (SEF) system, PTR MP5 Clone |
| Included Tools | 1/16" Allen Key, 3/32" Allen Key |
Best for
- Upgrading or replacing the safety selector on PTR MP5 clones with the FRT-RD3 trigger system
- Maintenance and repair of MP5-style firearm controls
What's in the box
- 1 x RD3 SEF Single-Sided Safety Selector - For use with the PTR MP5 Clone
- 1 x 1/16" Allen Key
- 1 x 3/32" Allen Key
Care
Frequently asked questions
- Is it compatible with non-PTR MP5 clones?
- No. This selector is specifically dimensioned for the PTR 9CT/9KT series of MP5 clone receivers. It may not fit other clone manufacturers like Zenith, POF, or MKE due to slight variances in selector channel depth and detent positioning. Always verify your receiver's specification against the PTR model before ordering.
- Does this work with the Freedom Finger™ M&P 2.0 trigger?
- No. This selector is exclusively for the FRT-RD3™ (SEF) system in the PTR MP5 platform. The <a href="/products/freedom-finger-m-p-2-0-forced-reset-trigger/">Freedom Finger™ for M&P 2.0</a> is a completely different system designed for a striker-fired pistol and uses no external selector lever.
- How long does shipping take?
- Standard processing time is 2-3 business days before shipment. Once shipped, transit via USPS Priority Mail typically takes 2-3 business days. International shipments to compliant destinations are handled case-by-case and can take 10-21 business days depending on customs.
- Can I return it if it doesn't fit my receiver?
- Returns are only accepted for uninstalled, unmodified components within 30 days of purchase, provided the product is in its original packaging. Due to the firearm component nature, items showing any signs of installation attempt (tool marks, wear) cannot be returned per company policy and ATF guidance on firearm parts.
- Does this require any fitting or gunsmithing?
- Typically, no. The component is a drop-in fit for in-spec PTR receivers. In rare cases where receiver tolerances are at the extreme limit, minor deburring of the selector channel with a fine-grit stone may be required, a process taking under 5 minutes. This is addressed in our technical tolerance framework.