MP5-22 A.R.T. Lever + Adjustable Anti-Bounce Buffer System
The MP5-22 A.R.T. Lever is an Active Reset Trigger component engineered specifically for the HK / Umarex MP5 .22LR platform.
This system installs directly into your factory .22LR MP5 trigger pack, requiring no proprietary housing, no permanent modification, and only minor fitment.
It is designed as a straightforward internal upgrade that enhances the performance of your existing trigger pack while maintaining true semi-automatic operation.
Once installed, the A.R.T. Lever actively assists trigger reset between shots, helping the shooter release the trigger faster so it can be pulled again as the bolt returns to battery.
• One round discharged per trigger pull
• Active reset between each shot for faster follow-up capability
• Maintains semi-automatic function
The system is designed to be easy to install and remove, making it an ideal entry-level upgrade for shooters looking to improve the responsiveness of the MP5 .22LR platform without replacing the entire trigger system.
Adjustable Anti-Bounce Buffer System
The MP5-22 A.R.T. platform incorporates an adjustable anti-bounce bolt system designed to accommodate a wide range of .22LR ammunition types, including:
• Subsonic velocity
• Standard velocity
• High velocity
This adjustable weight system allows the shooter to fine-tune bolt speed and timing, helping achieve the optimal operating balance for a specific MP5 .22LR setup.
Like other active reset systems, proper performance comes from balancing spring tension with bolt mass. By adjusting bolt weight and recoil tension, users can tune the system for smoother cycling and more consistent reset behavior.
The adjustable bolt weight system serves several important functions:
• Helps support reliable ignition
• Reduces bolt bounce during cycling
• Stabilizes bolt timing for smoother operation
• Helps reduce the chance of split casings, which can occur when excessive bolt bounce is present in direct blowback systems
This tuning capability allows the platform to run cleaner, smoother, and more consistently across different ammunition types once properly configured.
Factory Adjustable Recoil Spring Assembly
The MP5 .22LR platform already includes a factory method for adjusting recoil spring tension, which can be accessed with a standard Allen wrench. This built-in adjustment allows shooters to increase or decrease recoil spring tension, making it possible to further fine-tune the firearm’s cycling characteristics.
When combined with the adjustable bolt weight system, users gain two critical tuning points:
• Bolt mass adjustment
• Recoil spring tension adjustment
Together, these allow the shooter to dial in bolt speed, timing, and reliability for their specific ammunition and setup.
Ammunition Considerations
For best performance, standard velocity .22LR ammunition typically performs extremely well once the system has been properly tuned.
Certain ammunition types should be avoided, specifically:
• CCI Stingers
• CCI Mini-Mag
• Other extended-case .22LR cartridges
These rounds use longer casings than standard .22LR, which may prevent the round from fully seating in the chamber of the MP5 .22LR platform.
Improper seating of a round can cause the risk of casing bulging or splitting resulting in an out of battery discharge & potentially a squib malfunction.
Always check your barrel after any malfunction
For that reason, standard-length .22LR ammunition is strongly recommended.
Once the system has been properly tuned, standard velocity CCI ammunition is the recommended choice for the most consistent and reliable performance.
A full tuning guide and video walkthrough will be provided to help users properly dial in bolt weight and spring tension.
Please refer to our blog posts for additional setup information.
Factory Extractor Considerations
Due to the operating characteristics of the .22LR MP5 platform, the factory extractor has been widely discussed in the builder community for occasionally contributing to reliability inconsistencies. Reported user observations have included:
• Extractor tension allowing the case rim to slip during cycling
• Cases hanging or deforming under certain ammunition pressures
• In rare instances, reports of extractor engagement contributing to out-of-battery ignition events with a stock trigger installed
Because of these documented behaviors, the MP5-22 A.R.T. Lever system is designed to operate without the factory extractor installed, simplifying the cycling dynamics of the platform by removing an unpredictable variable.
Each MP5-22 A.R.T. Lever is backed by a lifetime warranty and serves as the foundation for a growing line of accessories designed to further optimize firearm systems.
Simple tuning.
Adjustable performance.
Built to run.
Note: This system does not run well suppressed due to low bolt weight.
Safety glasses and hearing protection should be worn at all times.
Standard velocity CCI is the recommended ammunition.
