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Vector MP5-40 feeding issues.

3K views 7 replies 2 participants last post by  MaadiMan 
#1 ·
I just finished building an MP5-40 parts kit on a Vector V89-40 reciever. When I finished up and went to the range to do the shakedown run, I couldn't get it to feed. At all. When I drop the bolt, the round starts to feed forward, but it doesnt start to funnel into the chamber. Instead, it feeds straight forward out of the mag into the side of the barrel at the breachface. This happens with enough force to mash the bullet back into the case 1/16" to 1/8". At first I thought that maybe I was sold the wrong magazine with this kit, but after doing some research I understand that the 40, 10 and 357 MP5's all take the same mag. (My mags are both no name black plastic things.)

I looked at a factory Vector the other day. The feed ramp (or maybe more rightly called the "feed funnel") was opened up a little wider than on my barrel. I want to make sure there are no other options before I start taking material off the barrel. Any suggestion where to start?
 
#2 ·
I figured it out. The barrel trunnion I used was different than the German 1-piece design. The bullet guides are milled integrally to the trunnion on German guns. The one I used was a US made one that, little did I know, was a 3-piece design. The trunnion is milled first, then the two bullet guides are pressed, then welded in.

So, it sucks to be me, because I welded in the trunnion without any bullet guides in. I think I will still be able to get them in without having to tear out the trunnion, though. It'll just be a ton of fun!

This is the pic I stumbled across that tipped me off:
 

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#4 ·
I got the two bullet guides installed last night (after building one of them from scratch out of a chunk of tool steel I had laying around). I took it out to the range and now it feeds perfectly! I have an ejection problem, though. I think I have it figured out, but It'll be a few days before I can escape to my home on the range to try it out again.
 
#6 ·
Well I guess it was an easier fix then you made it sound like :D
Well, the fix I cooked up is not factory original, in that I had to drill a hole through either side of the reciever, pressed in the bullet guides, then plug welded the guides to the trunnion and the reciever. These three-piece trunnions are supposed to be welded together befor being installed in the reciever, so I now have two extra welds on the outside of my gun, but it wont look out of place once I get everything sandblasted and Duracoted.


Good to hear you got it feeding now, when you get it all done please post a pic or two.
Will do. I'm pretty proud of this build. There aren't too many people doing them, and as such there isn't nearly the wealth of info online as there is for AKs.
 
#8 ·
I finally got it running right. It turns out that the bolt head was out of spec, so it would wobble on the ejection stroke, and if it wobbled just right, the ejector would be in the very bottom of the ejector channel, causing it to miss the case, resulting in a jam. I changed the bolt head, and viola!, runs great!

I have another MP5-40 kit to build, now that I've figured out some of the intricacies of these HK builds. The next one will be a carbine style, with a pinned on phony suppressor and a buttstock.

Here's the first build, the one that gave me all the grief:
 

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