A while back I posted here asking what tools people recommended keeping on hand for maintaining the MP5 platform. After some trial and error with those recommendations, plus getting five of these up and running, four with FRTs, I figured I'd put together the list I wish I'd had when I started.

Tools I'd recommend having:

• Bench block puck
• Punch set (Rennsteig is fine)
• Holex feeler gauge
• Small rubber/plastic non-marring hammer
• Rubber mallet
• Bench vise
• Rear sight tool for diopter sights
• Stainless steel pick set
• Annie's Arms MP5 Magazine Tool
• Annie's Arms HK Sear / Hammer Catch Tool
• MP5 SMG LULA loader & unloader

Not technically a tool, but extremely useful to have hanging in the workshop:

• MP5 exploded-parts diagram poster

Note: This is obviously in addition to the usual stuff you need for maintaining any firearm: grease, lube, cleaner/solvent, patches, brass brushes, etc., which you likely already have if you're getting into this platform.

Parts I'd recommend buying or at least sourcing on Day 0:

These are the parts that frequently go out of stock right when you actually need them.

• HK Extractor – MPN 21441
  • No, in my experience RCM is not necessarily "just as good." I thought it was until I personally ran into an extraction issue where replacing the extractor with an RCM part didn't solve it, but installing the HK extractor immediately did.
• HK Extractor Spring – MPN 206645
  • That said, the FMP HK-contract extractor springs have been indistinguishable from HK OEM in my experience so far. YMMV.
• HK Ejector Lever, 3rd Gen – MPN 201639
  • Again, based on my experience, PTR is not "just as good."
• HK Ejector Spring – MPN 200478
  • Same story here. I would buy the HK part rather than assuming the MKE spring is equivalent.
• HKP Ejector Lever Axle – SKU HKP-20630
  • This is one area where I've found the HKP part perfectly acceptable instead of paying for HK OEM.
• RCM locking pieces
  • For an MKE, which normally comes with a 120° locking piece, I'd keep 80°, 90°, 100°, and 110° pieces available.
  • For an HK, I'd keep 80°, 90°, and 110°.
  • If you have no intention of shooting suppressed, you can probably skip the 80° and 90° pieces and concentrate on 100° and above.
• A spare compatible trigger housing if you're installing an FRT or other drop-in trigger assembly
  • If you're going to replace the factory trigger assembly, consider buying another housing compatible with your stock setup and keeping the original components assembled as a complete lower. It makes troubleshooting substantially easier and gives you a quick way to return the gun to a known factory-style configuration when needed.

One point I want to emphasize because I see the opposite advice fairly often:

THERE IS NO NEED TO PREEMPTIVELY REPLACE PARTS THAT HAVEN'T FAILED.

A lot of these are wear items that you will eventually need, though, and several of them have a habit of being unavailable when you finally need one. Buying them ahead of time or getting them on backorder is prudent. Replacing perfectly functional factory parts just because you bought spares is not.

Feel free to add anything I've missed, especially platform-specific tools or parts that you've found useful over time. The goal here is to build the kind of practical reference for people getting into the MP5 platform that we all wish we'd had when we started.

Thought this might be useful to others. As my AP5 collection grew to include an AP5, AP5-P, AP5-N, and AP5P-N, I went through a lot of trial and error separating normal break-in issues from actual parts problems.

After a lot of testing, this is the process I’ve settled on. It has saved me time, ammo, and unnecessary troubleshooting.

The biggest thing: don’t install an FRT until the gun is completely broken in. Establishing a reliable baseline first makes diagnosing problems dramatically easier.

My break-in procedure:

• 200 rounds of 9mm NATO. If the final 100 are flawless, move to:
• 100 rounds of standard-pressure 124 gr. If those are flawless, move to:
• 100 rounds of 115 gr.
• Finish with another 50 rounds of NATO to confirm everything is still running reliably.

If you encounter failures at any point, stop at that stage and replace the following parts one at a time, testing after each replacement:

1. Genuine HK extractor spring
2. Genuine HK extractor
3. Genuine HK ejector lever

Before moving to the next ammunition type, I make sure the gun completes 100 consecutive rounds of the current stage without a malfunction.

Following this process gives me a known-reliable baseline before adding an FRT, a suppressor, or both.

If you choose a Rare Breed FRT-RD3, you’ll need an ejector lever, ejector lever spring, and ejector lever axle for the new trigger pack. You can pull those parts from the factory pack, but I recommend buying a separate set so you don’t have to cannibalize it. I use genuine HK for the ejector lever and spring, but the HKP axle is perfectly adequate and saves a few bucks.

Doing it this way has two benefits. First, it proactively addresses one of the more common weak points in AP5s, although in my experience only about half ultimately need the MKE ejector lever replaced. Second, it keeps the factory trigger pack intact, making it easy to swap back for troubleshooting, travel to states where FRTs are prohibited, or any other reason.

I eventually bought extra trigger housings for both sizes so each factory trigger pack remains assembled in its own housing. Swapping the entire lower takes seconds instead of requiring trigger-pack disassembly every time.

One other useful point for anyone with multiple AP5s: the lowers are interchangeable within each size.

• AP5-P and AP5P-N lowers fit the K-sized uppers.
• AP5 and AP5-N lowers fit the full-size uppers.

Just keep K lowers with K uppers and full-size lowers with full-size uppers.

This process has worked well across several AP5 variants and has made troubleshooting far more systematic than swapping random parts and hoping for the best.

I’m intentionally not getting into locking pieces here. This process is meant to establish reliability in the factory configuration before adding or breaking in an FRT, a suppressor, or both. Locking-piece selection becomes relevant after that baseline has been established and depends on the specific configuration.

Add anything else you’ve found useful during the clone break-in period. Consolidating the proven practices in one place should help the next person avoid wasting time and ammunition chasing the wrong problem.

Just ordered an AP5-P Navy. Atlantic had their last one in stock on sale for $1,149, so I couldn’t pass it up.

That rounds out my current collection:

• AP5 (A2 configuration)
• AP5-N (SD-style with HK Bryce adapter, SD handguard, and MKE A3 retractable stock)
• AP5-P (B&T UMP-style side folder)
• AP5-P Navy (will get a Safety Harbor KES once the Form 1 clears)

Curious where everyone else is at. How many MP5 variants do you own?

View Poll

First suppressor. I opted for the Dead Air Wolfman from Bass Pro, shipped directly to me. Total time from order submission to delivery was 14 days, 18 hours, 30 minutes.

User Rating: 5 stars

For anyone considering the same process, here’s the timeline from my experience:

Mon, 4/13

• 8:00 PM: Order placed on Bass Pro site
• 8:20 PM: Email received from Silencer Central prompting account creation and profile completion. Email came from noreply@silencercentral.com and went to spam.
• 8:50 PM: Uploaded fingerprint EFT file and passport photo
• 8:52 PM: Received invitation to sign document: T&C V4
• 8:53 PM: T&C V4 signed

Tue, 4/14

• 6:47 AM: Passport photo validated

Thu, 4/16

• 7:19 AM: EFT fingerprints validated
• 7:32 AM: ATF Form 4 completed and submitted
• 7:32 AM: Received eForms Application Submission Notification from ATF
• 10:04 AM: CLEO notification acknowledged by CLEO
• 4:22 PM: Paper fingerprint card kit shipped via USPS. Notice received through USPS Informed Delivery. Shipper listed as BMADDOX ENTERPRISES, LLC DBA Silencer Central.

Sun, 4/19

• 4:16 PM: eForm 4 approval email received from ATF
• 4:17 PM: Silencer Central approval email received

Mon, 4/20

• 3:57 PM: UPS label created. Package not yet in UPS possession, but tracking was visible in UPS My Choice.

Tue, 4/21

• 11:35 AM: Received email from Silencer Central stating they were preparing to ship to the FFL in my state
• 1:35 PM: Paper fingerprint card kit received via USPS

Fri, 4/24

• 4:55 PM: Package dropped off at UPS Access Point by shipper
• 7:32 PM: Package entered UPS possession

Sat, 4/25

• 7:13 AM: Received email from Silencer Central stating the package had shipped to my door via UPS, with tracking number provided (already had it due to UPS My Choice)

Sun, 4/26

• 11:18 AM: Received email from UPS stating the package would be delivered the next day

Mon, 4/27

• 2:20 PM: UPS pre-arrival email received
• 2:30 PM: Package delivered. Physical signature required.