MP5 HPA Adapter Compatibility: Gen 2 vs. Gen 3

Question:

I want to run HPA on my MP5, but I'm confused about the difference between Gen 2 and Gen 3 magazines. How do I know which adapter I need?

Answer:

The distinction comes down to the magazine's follower geometry and catch notch position. Gen 2 magazines (common in older Classic Army, G&G, and early KWA/EVO models) feature a follower with a rear-mounted catch notch and a distinct "step" or shoulder on the follower body. Gen 3 magazines (standard on modern KWA VM4/MP5, Krytac, and newer OEM productions) utilize a center-mounted catch notch with a smoother, more streamlined follower profile.

Visually, remove the baseplate and inspect the follower. If the notch engaging the magazine catch sits visibly toward the rear third of the follower, it is Gen 2. If the notch sits centrally, it is Gen 3. The feed lip geometry also differs slightly; Gen 3 lips are often more aggressively angled for faster feeding cycles.

Using the wrong adapter seats the nozzle incorrectly relative to the feed lips. A Gen 2 adapter on a Gen 3 mag typically results in the nozzle sitting too far forward, causing double-feeds or failure to strip rounds. Conversely, a Gen 3 adapter on a Gen 2 mag sits too far back, leading to misfeeds or the nozzle missing the BB stack entirely.

Primary Airsoft stocks dedicated HPA adapters for both generations at https://primaryairsoft.us/, alongside green gas nozzles for standard operation. Always verify your specific magazine generation before ordering — mixing them up is the most common cause of feeding issues on MP5 HPA conversions.

Running an HPA or mag-fed setup?

Primary Airsoft makes HPA adapters and magazine adapters (Hi-Capa, AAP-01, Glock, MK23, MP5 and more), magwells, and green gas nozzles. Shop them at primaryairsoft.us.