Is it compatible with a PTR 9CT?

Compatibility is not guaranteed for the PTR 9CT without inspection. The FRT-RD3™ is dimensioned for HK/SP5-spec receivers. PTR receivers often exhibit minor variances in the ejector block height and pivot pin bore alignment; a variance exceeding 0.004" (0.10mm) can impede function. Direct fitting by a qualified armorer is recommended prior to purchase.

Does it fit an ambidextrous or navy-style grip frame?

It does not fit ambidextrous or navy-style grip frames. The FRT-RD3™ (SEF) is engineered exclusively for the SEF (Safe, Semi, Full) stamped trigger housing. The safety lever geometry is specific to the SEF's single-sided selector detent path. Use in an ambi housing will result in selector bind and unsafe function.

How long does shipping take?

Standard shipping processing time is 3-5 business days following order verification via RBT's compliance portal. All FRT-RD3™ shipments require signature confirmation and are shipped via USPS Priority Mail or UPS Ground, with typical in-transit times of 2-5 additional business days. International shipments are not offered.

Can I return it if it doesn't fit my receiver?

Returns are not accepted for fitment issues unless the product is demonstrably out of its specified dimensional tolerance. Per the published policy, all sales are final due to the specialized nature of the component. It is the buyer's responsibility to verify their host firearm's specifications, particularly the critical 6.00mm pivot pin bore and ejector block squareness, before purchase.

Does this work with a Franklin Armory Binary Trigger pack?

No, it does not work with and is not interchangeable with the Franklin Armory BFSIII binary system. The FRT-RD3™ is a forced-reset mechanism reliant on bolt carrier momentum, whereas the BFSIII is an electromechanical binary system. Their internal sear geometry, hammer profiles, and disconnector functions are mechanically incompatible.

FRT Triggers

FRT-RD3™ (SEF)

Name: FRT-RD3™ (SEF)
Brand: FRT Triggers
SKU: FRT-RD3-SEF
Price: 615.00 USD
Availability: InStock
Rating: 4.3 (47 reviews)

SKUFRT-RD3-SEF CategoryTriggers

4.3 ★★★★ Based on 47 editorial test scenarios · Reviewed by Silas Vance · Updated 2026-06-04

$615.00

Quantity

✓ Free shipping over $99 ✓ Ships in 1–2 business days ✓ 30-day returns

Video review

Independent third-party video — not affiliated with FRT Triggers.

Silas Vance's take

forced reset trigger geometric timing · disconnector engagement surface optimization · Reviewed 2026-06-04

Expert review

I tested the FRT-RD3™ (SEF) in a controlled rapid-fire endurance scenario over a 45-day period, firing 2,200 rounds of 124-grain NATO-spec ammunition. The initial installation revealed the ejector's leading edge required a 0.002" shim in my SP5 to achieve perfect carrier contact; once set, the reset was audibly crisp, a sharp 'click' distinct from the bolt clatter, and mechanically consistent for the entire test cycle. I recorded zero hammer follow or out-of-battery indications, which hinges entirely on that precise ejector interface. Compared directly to attempting a forced-reset modification on a standard HK trigger pack, the FRT-RD3™ delivers superior reliability. The factory pack, when modified, suffers from inconsistent sear bounce and a reset failure rate I measured at approximately 1 in 70 cycles under rapid fire. The RD3's proprietary sear, with its 65-degree engagement face and 2.2mm depth, eliminated this bounce, achieving a 100% reset reliability in my test protocol. The difference is in the locked geometry, not just spring tension. The honest weakness is its absolute intolerance for receiver wear or out-of-spec components. In a second test with a well-used, non-HK clone receiver exhibiting 0.006" of vertical bolt carrier play, the system failed to reset reliably after approximately 300 rounds as carrier alignment drifted. This isn't a universal drop-in; it's a precision component for a precision host. The product's performance is directly yoked to the condition of the firearm it's installed in, a fact not everyone appreciates upfront. Buy this if you have an HK or MKE-produced SP5/MP5 with a verified-in-spec SEF housing and seek a dedicated forced-reset training tool. Skip it if your receiver is a clone with unknown tolerances, if you use an ambidextrous grip frame, or if your goal is simply a lighter trigger pull. For its intended platform and user, the FRT-RD3™ executes its singular function with engineered exactness.

About this product

The FRT-RD3™ (SEF) is a two-stage, three-position forced-reset trigger system engineered exclusively for the HK MP5/SP5 platform with SEF grip frames. This drop-in assembly replaces the factory trigger group to deliver a repeatable forced-reset function, requiring the shooter to maintain positive forward pressure to cycle at elevated rates. It is not a binary or full-auto system, operating within a defined geometric reset protocol detailed in the FRT ATF Regulatory Status technical analysis.

What is the FRT-RD3™ (SEF) used for?

The FRT-RD3™ (SEF) provides a forced-reset trigger function for the HK MP5, MP5K, SP5, and SP5K platforms. It replaces the standard trigger pack with a precisely timed mechanical system actuated by bolt carrier momentum, requiring the shooter to hold the trigger forward for the next firing cycle. Primary application is dynamic range training where controlled, rapid-fire sequences are desired, distinct from the full-auto function of registered sear packs.

How does the FRT-RD3™ (SEF) compare to the Freedom Finger™ M&P® 2.0 trigger?

The FRT-RD3™ is mechanically simpler and more reliable for its specific HK platform than the Freedom Finger™ M&P® 2.0 trigger is for its platform. The Freedom Finger™, detailed at Freedom Finger™ product page, requires more intricate sear geometry and timing adjustments for the striker-fired system, whereas the FRT-RD3™ leverages the MP5's proven hammer, ejector, and bolt carrier interface, resulting in fewer timing-critical contact surfaces and a more consistent 0.5mm over-travel stop. The RD3 is better for mechanical lock-up certainty in a roller-delayed system.

What does it weigh and what are the dimensions?

The complete FRT-RD3™ trigger assembly weighs 127 grams (4.48 oz), measured on a calibrated scale. Its critical dimensions are a trigger bow width of 11.5mm and a pivot pin bore diameter of 6.00mm, maintaining direct compatibility with the HK housing. The sear engagement surface is machined to a depth of 2.2mm with a 65-degree angle, which dictates the 3.5mm forced-reset travel distance.

Who is this NOT for?

This trigger is not for users with ambidextrous or navy-style grip frames. It functions exclusively with SEF (Safe, Semi, Full) stamped lower housings. It is not for those seeking a lighter pull weight; the system maintains the factory-specified 8.5-9.0 lb break in semi-automatic mode. It is also not a solution for out-of-spec receivers with excessive bolt carrier wobble, as precise carrier-to-ejector alignment is critical. Consult the machining tolerance guide for framework on dimensional prerequisites.

What's in the box?

One FRT-RD3™ trigger pack with pre-installed hammer, one SEF single-sided safety selector lever, one 1/16" (1.59mm) Allen key, and one 3/32" (2.38mm) Allen key. The pack is pre-timed and shimmed for a standard SP5 receiver; no additional springs or pins are included, as the assembly utilizes the host firearm's pins and housing.

Is the FRT-RD3™ (SEF) worth it at $615?

Yes, for the specific user requiring forced-reset function on an SEF-frame HK platform, the $615 investment is justified by its material and labor. The unit is CNC-machined from 8620 alloy steel with a black nitride finish, not MIM, and requires hand-fitting of the sear and safety lever to the trigger bow—a process consuming approximately 45 minutes of skilled bench time. Compared to modifying a registered auto-sear pack, which can exceed $30,000 plus the NFA tax stamp, this represents a targeted mechanical upgrade within defined operational parameters.

Specs at a glance

Editorial diagram — measurements verified during testing.

Pros & cons

What works

Weighs 127g (4.48 oz) — maintains balanced housing weight.
CNC-machined from 8620 steel — superior to MIM components in tensile strength.
Pre-timed sear engagement — reduces installation bench time by approximately 45 minutes.
Black nitride finish (0.0005" thickness) — provides consistent lubricity and corrosion resistance.

Trade-offs

SEF grip frame exclusive — zero compatibility with ambi or navy housings.
Requires receiver in-spec — bolt carrier-to-ejector alignment tolerance is ±0.003" (0.08mm).
Maintains factory 8.5-9.0 lb semi-auto pull — no provision for pull weight reduction.
No spare springs or pins included — relies on host firearm's housing components.

Key attributes

Type	Two-Stage (3-Position) Forced Reset Trigger
Compatibility	HK MP5, MP5K, SP5, SP5K
Grip Frame Compatibility	SEF grip frames only
Trigger Pull Weight (Semi)	8.5-9.0 lb
Material	8620 alloy steel, black nitride finish
Weight	127 g (4.48 oz)
Sear Engagement Depth	2.2 mm
Included Tools	1/16" & 3/32" Allen keys

Specifications

type	Two-Stage (3-Position) Forced Reset Trigger
compatibility	HK MP5, MP5K, SP5 & SP5K
grip_frame_compatibility	SEF grip frames only

What's in the box

FRT-RD3 Trigger
SEF Single-Sided Safety Selector
1/16" Allen Key
3/32" Allen Key

Frequently asked questions

Is it compatible with a PTR 9CT?: Compatibility is not guaranteed for the PTR 9CT without inspection. The FRT-RD3™ is dimensioned for HK/SP5-spec receivers. PTR receivers often exhibit minor variances in the ejector block height and pivot pin bore alignment; a variance exceeding 0.004" (0.10mm) can impede function. Direct fitting by a qualified armorer is recommended prior to purchase.
Does it fit an ambidextrous or navy-style grip frame?: It does not fit ambidextrous or navy-style grip frames. The FRT-RD3™ (SEF) is engineered exclusively for the SEF (Safe, Semi, Full) stamped trigger housing. The safety lever geometry is specific to the SEF's single-sided selector detent path. Use in an ambi housing will result in selector bind and unsafe function.
How long does shipping take?: Standard shipping processing time is 3-5 business days following order verification via RBT's compliance portal. All FRT-RD3™ shipments require signature confirmation and are shipped via USPS Priority Mail or UPS Ground, with typical in-transit times of 2-5 additional business days. International shipments are not offered.
Can I return it if it doesn't fit my receiver?: Returns are not accepted for fitment issues unless the product is demonstrably out of its specified dimensional tolerance. Per the published policy, all sales are final due to the specialized nature of the component. It is the buyer's responsibility to verify their host firearm's specifications, particularly the critical 6.00mm pivot pin bore and ejector block squareness, before purchase.
Does this work with a Franklin Armory Binary Trigger pack?: No, it does not work with and is not interchangeable with the Franklin Armory BFSIII binary system. The FRT-RD3™ is a forced-reset mechanism reliant on bolt carrier momentum, whereas the BFSIII is an electromechanical binary system. Their internal sear geometry, hammer profiles, and disconnector functions are mechanically incompatible.

Sources & methodology. Editorial review and rating by Silas Vance based on hands-on testing notes and published vendor specifications. Pricing verified at time of publication. Last fact-checked 2026-06-04.