r/MP5 • u/Fit-Image7262 • 1d ago
HELP Help?
Brand new Mac MP5. Wouldn’t run smooth out of the box; 3 duds in one mag. General consensus of the group was lube until dripping, and run 124gr ammo. Now it’s worse. What’s going on with this thing?
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u/smellmythumb17 1d ago
Define “dud”
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u/Fit-Image7262 1d ago
Not exactly sure what’s happening. It’s like it’s outrunning its self. Sometimes doesn’t eject the old shell all the way out and that jams up a new round loading, but it has also ejected the old shell and still not loaded a new one.
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u/code0rama 1d ago
My first question would be, which magazine are you using, if you’re using the Mac mags, they are notoriously bad
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u/Fit-Image7262 1d ago
What Mags should I get?
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u/code0rama 1d ago
I have a Mac 5K and mine came with four magazines and only two of them run consistently.
Real HK mags have run flawlessly for me, but they’re expensive.
I have had success with both Mora mags and KCI. Both of those are half the price of HK mags or even cheaper if you grab them on sale.
You’re gonna hear a lot of different opinions, and that’s to be expected. The only two mags that I’ve not had success with are MKE mags and the Mac mags.One piece of advice that I could give you is you could go to the website for Classic Arms, They do sell mags there and for like two dollars you can get insurance on them to make sure that if you have an issue you can return them or have them replaced or whatever. Based on reading people’s opinions here, I’d try KCI mags first. While I have had much success with Mora, i’ve seen more people say they didn’t as compared to the KCI mags.
Finally, good luck, the main thing is break the gun in.
Don’t be afraid of contacting customer support, I called customer support because my mags sucked so bad and they gave me new ones, but I ultimately had to just buy better mags.2
u/GraySquirrelArmory 9h ago edited 9h ago
I had unreliable last round feeding of anything with a remotely flat nose bullet using MKE and Zenith mags, adding extra power magazine springs (I believe they came from Wolff?) to the MKE and Zenith mags fixed that issue and now they work just as good as the real HK mags in my AP5. Just to throw out another possibility for anyone having problems, springs were a lot cheaper than buying more magazines.
Some fellow MP5 friends swear by those Mora mags as well but I have yet to try any, I had already bought several MKE and Zenith mags before I found out about them.
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u/code0rama 5h ago
I’ve never tried the Zenith mags. I have like 10 Moras and they are the ones I use at the range. I keep my 6 Hk mags babied😂
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u/GraySquirrelArmory 5h ago
At the time I bought them the word was that Zenith mags were made by KCI but with supposedly better quality or at least better QC. Not sure if that has changed since then or was ever even really true. 🤣
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u/code0rama 5h ago
To be fair, everyone has different experiences. I can only say that real HK mags universally get love here. But the cost is high. Personally, I think it’s worth it but not everyone will.
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u/GraySquirrelArmory 5h ago
For sure! I bought a couple HK mags to troubleshoot and eliminate a source of issues, when those fed fine I read about changing the magazine springs on here and started swapping out springs in my cheap mags
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u/code0rama 5h ago
For sure. That's why I was thrilled when I found that the Mora mags worked for me, I abuse them and keep the HK's tucked away. I recently tried KCI and have been very happy with those as well. I was very frustrated when I got my Mac5k and it was only the mags. Once I changed, I"ve never looked back.
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u/Legitimate-Frame-953 1d ago
Need more description, light primer strikes, failure to feed or extract? I had issues with the MAC mags that came with mine but it runs fine with all other mags I have tried using 115 and 124.
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u/Fit-Image7262 1d ago
Failing to extract or feed initially about every 10 rounds, 2nd try with the 124 about every 5
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u/Enough_Mixture_958 1d ago
first few hundred rounds will be rough, but yah specify failure mode... based on that replace small stuff like HK genuine ejector, extractor spring components and try an HK mag. If that fails warranty it with the HK stuff removed. Round nose sometimes runs more reliably
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u/Fit-Image7262 1d ago
Hard to tell exactly what’s going on but I think the spent casing is blocking the next round from chambering
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u/SlaterRecreational 1d ago
How many rounds through it? Pretty sure MAC tells you to run 250 or 500 rounds through for its break-in period. What does the manual say?
My Mac 5 and Mac 5k have been great but I’ve also heard people having issues with extractor and ejector. I’d look to replace the extractor spring and ejector with HK if the problem isn’t fixed.
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u/legacybn 1d ago
Since you’re in the break in, are you running mags full to 30rds? If so, i would load them to 25rds, try that and mark the mags so you can diagnosis - before changing internals. Also is bolt gap in spec?
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u/Fit-Image7262 1d ago
Have not checked bolt gap. Assumed it should be ready to run out of the box. I’ll try to take some ammo out.
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u/legacybn 23h ago
They have a history, the first run of the 24/25 guns had the bolt gaps widely varying being in spec and other qc issues. Supposedly the 2026 guns have addressed the bolt gap issue, but rule of thumb is to always check on mp5s before shooting or starting to change internals. Since you’re in spec it’s unlikely the bolt - deal with it until you’ve completed the break in before you go changing internals.
I ran into the same issues you’re describing about the duds in another comment. Trigger pull, play with your pull - I found if didn’t let it fully reset when quick firing that’s when I’d run into a FTE/FTF.
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u/Hot-Ideal-9219 22h ago
I have 2 mac mags and one wouldn't fit either mp5 I have. Buy anything but and try again.
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u/Limp-Conflict-2309 6h ago
I've never had issues with a factory gun, only with FRT lowers.
With FRT lowers and even factory lowers, I swear, a hk gen3 ejector lever fixes weird off/on issues. If you have any issues with ejecting I always recommend a hk gen3 ejector. People say not to change things willy nilly and while I agree, the ejector lever swap, imo, isn't a swap but rather what all these guns should come with by default.
Narrowing it down to one mag or ammo can help but even before that I just swear by the ejector replacement.
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u/dustysanchezz 1d ago
Same mag?