MP5 FRT 2026: Best Forced Reset Triggers for MP5, SP5 & AP5

A forced reset trigger uses the bolt carrier's rearward travel to mechanically push the trigger back into reset after each shot, then holds it there until the action returns to battery. Every round still requires its own deliberate trigger press, which is exactly what keeps the FRT a semi-automatic trigger: one press, one round. The mechanism just removes the slow, sloppy part of a fast string, the manual finger reset between shots, and replaces it with a positive mechanical reset driven by the gun's own cycle. The result feels rapid, but it is the shooter, not the trigger, firing each shot.

On the roller-delayed MP5 the implementation splits two ways. A drop-in cassette like the Rare Breed FRT-RD3 packages the entire forced reset mechanism into a single self-contained unit that replaces the factory fire control parts. The AS Designs ARHK is an announced cassette on the same principle, built on the ARC-Fire mechanism for MKE-pattern clones and the G3 family; AS Designs has not put it on sale. The other route converts the gun to an AR-15 fire control group inside an MP5-pattern lower and adds a Super Safety selector plus a bolt-carrier slip/trip. The Super Safety is a selector, not a trigger; its added third position is what enables forced reset, while the slip/trip is the part the bolt carrier acts on to drive the reset. To go deep on how Super Safety selectors and forced reset triggers actually work, read our Super Safety guide, and for the full forced reset landscape across the AR, AK, and MP5 platforms, see our forced reset trigger buyer's guide and our FRT compatible guns guide, which maps every host platform with a forced reset path. For the AK and Ruger sides of the non-AR forced reset category, our AK forced reset triggers guide and our Ruger forced reset triggers guide cover those platforms, our M&P forced reset triggers guide covers the Smith & Wesson polymer pistol side, our Canik forced reset triggers guide covers the striker-fired TP9, METE, and SFX Rival pistols, and the bullpup FN PS90 forced reset triggers guide covers the Dorin XPRT90 and Duality Arms RATL-R on the 5.7x28 PS90. If you want a 9mm AR instead of a roller-delayed MP5, the AR9 FRT build guide walks the blowback tuning that a direct-blowback 9mm AR needs. The other open-bolt-fast PCC host with a real forced reset market is the MAC, and our MAC-10 / MAC-11 FRT install guide covers the Cobray and MPA Defender fitment split. Elsewhere in the HK line, our HK UMP FRT guide covers the GDI-3D reset-capable lower kit.

Buy the drop-in cassette if you want the least work. The Rare Breed FRT-RD3 replaces the factory fire control parts as one self-contained unit with no AR fire control group, no separate selector, and no slip/trip to time. It runs $615 for the SEF version and $620 for the AMBI, with a one-per-customer, one-per-24-hours purchase limit, and it is the fastest route to a running gun for an HK MP5, MP5K, SP5, or SP5K with a frame that matches the selector pattern you order.

Buy a complete lower if you want turnkey and you are fine paying per gun. The Mars Trigger lower ($599.95) arrives with the AR fire control group and Hoffman Super Safety selector already installed and timed, so it runs the moment you pin it into the gun. The War Hammer lower ($625) is built from Kevlar and carbon-fiber-reinforced polymer instead of billet aluminum, which shaves weight against an aluminum lower, with the broadest host coverage. Either way you are buying a lower per firearm, not a part you can move between guns.

Build an AR-fire-control-group lower if you want the cheapest and most modular path and you do not mind assembly. The AS Designs full kit ($399.99) is the best-value complete version: a billet 7075-T6 lower with your choice of Super Safety M2 or Arc-Fire V2 selector, an AR fire control group, and the Slip Trip V5 included, undercutting both finished lowers. The Trinity Trigger kit (from $199.99) bundles the trip, cam, lever, and trigger but assumes you already own an AR-fire-control-group MP5 lower; it does not work in a stock factory housing. The bolt-carrier trips are the cheapest pieces in the ecosystem, the War Hammer aluminum trip ($98.95) and the AS Designs titanium Slip Trip V5 ($99.99), and they only make sense to finish or refresh an existing Super Safety system. Configure any of these into a complete roller-delayed 9mm build in our rifle builder. Once the trigger is sorted, the mounts, stocks, magazines, and controls that round out the gun are in the MP5 accessories & upgrades guide. For a neighboring roller-delayed and PCC upgrade comparison, the B&T APC9 accessories guide and the cheaper Grand Power Stribog accessories guide cover the same upgrade logic on adjacent hosts.

Nothing above fits the rimfire Umarex HK MP5 .22 LR. It is a .22 with its own trigger pack, so its forced reset triggers are separate products. URSA-SEC sells a rapid reset system for the A5, SD, and K versions with the factory trigger pack, in steel or a cheaper carbon-fiber nylon you can modify while dialing in fitment; it works with the factory two-position safety and does not fit the GSG MP5 .22. Continental Customs sells a stainless version built as a permanent install and a cheaper PETG-CF friction-fit drop-in.

URSA states its part is not plug-and-play, calls for fitting and tuning, and warns of out-of-battery ignition with inconsistent rimfire ammunition, so feed it one consistent load and function-test on the range. Continental Customs says its PETG-CF drop-in may need minor sanding, and it sells the stainless version as a permanent install. Prices run from $34.99 to $69.99, a fraction of any 9mm MP5 option. For forced reset on other rimfire hosts, see our 10/22 FRT guide and AR22 FRT build guide.