So I recently traded a few guns for a Vector MP5/40.  Serial number is under 120, not sure if that is considered "low" or "high" for this gun. No SW markings on it. Finish seems to be a shiny paint-like substance that seems to chip off of the gun. Unsure of who built it.

Current issues are:
1. FTF - Probably the magazine, as it's a crappy aftermarket black one with an apparent cracked feed lip. I already have 4 brand-new HK MP5/40 magazines for it, which fit in the magwell fine, and feed great, BUT this brings me to the second issue.
2. The HK factory magazines will not lock into the gun. It almost seems like the magazine well is either too long, or the magazine catch is too tall, both, or maybe the factory magazines are out of spec, which I doubt.
3. Sporadic FTE hand cycling. When it DOES feed fine, the bolt doesn't always let go of the cartridge, but if I cycle it enough it eventually tosses the cartridge 8 feet away from the gun.


What I have already done:
1. Swapped the recoil spring for a factory HK MP5/40 spring I got from HKP.
2. Ordered (but not received yet) a factory HK MP5/40 ejector, ejector spring, extractor spring.
3. My original plan was to remove the paddle mag release and carefully shave off material until the factory magazines would work.....until I realized that it's apparently welded into the gun. Derp.


This is my first MP5 clone, so I'm genuinely at a loss of what to do. Not a whole lot of information on the internets concerning the Vector MP5/40 troubleshooting that I could find. Any tips would be appreciated.

Are you inserting the mag with the bolt open or closed?

Manuel of Arms is to NEVER insert a mag on a closed bolt on the MP5 platform.

So that era of gun can have a lot of issues.  I had to replace the bolt head, my bolt face was an oval and caused FTE.

Replaced with a RCM bolt and HK extractor spring, extractor and ejector lever.

The mags not locking is a very common issue as was the mags setting too deep and the bolts whacking the back of the magazine leading to wear. I still have a 9mm clone that about every other mag will lock in and a bunch won’t.  

I am not an expert, but I believe there is some ability to adjust the catch without actually shaving it down.  

They can be great guns but sometimes you have to enlist the help of a competent builder to get yours into spec.  Others with more knowledge will be along with better answers.

Pile of money + quality H&K smith = happiness

Bought one of these new (SBR) in 2008.

Biggest issue is magazines. The aftermarket ones sold by Vector / with the gun suck.

Mine had the same issue with the HK not being able to lock in. In my gun the magwell itself was too tall. A good local gunsmith trimmed a small amount of material from the bottom of the magwell until the HK mags could lock in.

After that modification it runs ok with the HK mags and decent brass cased ammo.

AFAIK the other parts you swapped were original HK from the parts kits they were built from.

I had one of the Vector clones in 10mm, and it never worked very well.  I noticed the locking piece was not the number used on the the 10mm (either the hi or low impulse version).  It was one from a 9mm.  Called Vector, and was told they used any locking piece they could and "just ground it down to work".  Uhh, don't think that's how it's supposed to be done.

Among the other issues you're working on, check out the LP number, and compare it to what's supposed to be on the 40 cal version.

Good luck.

Well, the locking piece in mine is marked "low" so I guess I got lucky there.

""This is my first MP5 clone, so I'm genuinely at a loss of what to do. ""

Send it to a reputable MP5 smith

Can you recommend one?

Try Ralph Jr? He's HK Ralph Jr on instagram

Are the bullet guides and your trunion in good shape?

Vector, Coharie, and SW guns in .40 and 10mm had a nasty habit of fracturing bullet guides

Ghillie bear.

918-696-8715
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Jeff specializes in clones. I would highly recommend him.

Scott