The MG34 Repair and Troubleshooting Thread

223762 said:
this thread has completely turned into a repair thread now. Too bad TNW is such a sh!ty company.

1340. the bolt has to glide like butter in the receiver, so check your bolt wheels and the receiver for imperfections like rough spots or a tight fit for the wheels to squeeze through your receiver.
It could also, and most likely, be your ejector binding on your ejector plate. Check where the bolt is being stopped and try to determine where the ejector pin could be at that point. If your ejector plate has any wear on the ramp, it should be replaced.

lets get all these MG34's running! yes, its a labor of love, don't give up.:50cal:
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Maybe Dilligaf can rename the thread again to be the mg34 repair thread lol
 
Desert_Fox said:
I have the new Marstar parts. They don’t fit the old style of sear ring. The picture I posted was of the new style sear and sear ring assembly. The old style doesn’t have the shelf which changes the fulcrum point of the sear lever and makes the trigger pull lighter.
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I figured i would post this picture so everyone can see the difference between the old and new parts (old style on the left). The new style drastically reduces trigger pull weight. Hopefully someone here can hook Desert_fox up.

aBOVQ1V.jpg


lol i just noticed the thread title did change.
 
Deathrawt said:
As was stated check the bolt rollers to make sure they are good and not sloppy, one of mine got so sloppy that the circlip in the bolt wouldn't hold it in and caused it to jam in the reciever.
Check the ejector and ejector plate it may be binding. If you can remove the ejector put the bolt back in the gun and manually cycle the bolt with the charging handle to see if the bolt body snags or drags on the ejector plate. I had this problem too
One more thing to try is to remove the spacer tnw put on the end of the recoil spring. Sometimes the main spring can bind up
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There was a spot in my receiver where the bolt was sticky. I polished that spot, so now the bolt moves in the receiver very smoothly.
The rollers appear to be good, but will double check them.
This problem only occurred while shooting. The bolt hung up at the very back of the receiver, further back than the safety holds the bolt.
It took very little pressure on the cocking handle to release the bolt. I did have the flashhider snugged up tight. Maybe too tight.
After polishing the sticky spot, I cycled the bolt several times as hard, fast and as far back as possible. and couldn't duplicate the problem.
Next time I go shooting I will check the ejector pin and plate to look for binding there if it hangs up again.
I have some fired brass I'm going to cycle through my gun to see if it will bind doing that.
I did notice all the ejected brass is flattened on one side for about 2/3 of the cartridge.
I will check the buffer spring spacer too.
 
1340 said:
There was a spot in my receiver where the bolt was sticky. I polished that spot, so now the bolt moves in the receiver very smoothly.
The rollers appear to be good, but will double check them.
This problem only occurred while shooting. The bolt hung up at the very back of the receiver, further back than the safety holds the bolt.
It took very little pressure on the cocking handle to release the bolt. I did have the flashhider snugged up tight. Maybe too tight.
After polishing the sticky spot, I cycled the bolt several times as hard, fast and as far back as possible. and couldn't duplicate the problem.
Next time I go shooting I will check the ejector pin and plate to look for binding there if it hangs up again.
I have some fired brass I'm going to cycle through my gun to see if it will bind doing that.
I did notice all the ejected brass is flattened on one side for about 2/3 of the cartridge.
I will check the buffer spring spacer too.
Click to expand...

The flattening of the brass can occur on ejection (downward) where the brass collides with the shooting bench. Mine can ding the case necks pretty well. If the brass is being flattened 2/3 of the length of the case, plus the bolt binding as you described, this may point to high recoil velocity in the bolt. This could be due to either (a) hot ammo - some of the surplus loads floating around are loaded pretty hot; and/or (b) a small booster cone. TNW is notorious for using small (9mm) hole diameter recoil boosters in the MG34 to get marginal guns to cycle. The original booster cones are markedly larger in hole diameter - 11.5 or 12mm. I picked one up for $20 and it works great. In combination with a German firing pin that uses less recoil energy to ####, my MG34 runs smoother and isn't beating itself to death.
 
I have my recoil booster drilled to .450".
I lubed everything up really well before shooting so there would be less friction.
I was shooting surplus ammo, which like you said is hot.
I have some other ammo I can try.
Also, Irunguns has the .308 conversion listed for $750 US.
I pulled the trigger and ordered a kit.
 
Im not sure the 308 conversion will help solve your issue. I would bet that your ejector pin is binding on the underside of the ejector plate. fitting the ejector pin and plate is very important. if both parts are not fit together perfectly they will beat each other up in no time.
When TNW assemble these guns they don't do any real finishing work. i have even seen ejector plate screws that where too long and the bolt would hit them every time it passed by them.
you can try greasing up all the parts and hope it breaks itself in, but it could just make it worse.

If you want, i could post some pictures later of parts that I have had fail, to highlight some areas that can cause similar issues.
 
223762 said:
If you want, i could post some pictures later of parts that I have had fail, to highlight some areas that can cause similar issues.
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I didn't order the .308 kit to solve this problem. I bought it because I have crates of .308 ammo, and the questionable quality of some 8mm ammo.
I would love to see any photos you could post. As you said the ejector pin and plate need to be checked to see if they are binding. This problem occurred the last time I went shooting, and didn't happen in previous shooting sessions even with the booster cone unmodified.. The other thing I was thinking is I had the flashhider snugged right up tight which may have caused hard recoil?
 
1340 said:
I didn't order the .308 kit to solve this problem. I bought it because I have crates of .308 ammo, and the questionable quality of some 8mm ammo.
I would love to see any photos you could post. As you said the ejector pin and plate need to be checked to see if they are binding. This problem occurred the last time I went shooting, and didn't happen in previous shooting sessions even with the booster cone unmodified.. The other thing I was thinking is I had the flashhider snugged right up tight which may have caused hard recoil?
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oh i see. the 308 is a great kit to have.
Having the flash hider on tight is a good thing. i only hand tighten it, but sometimes it needs some encouragement to unscrew. if you drilled out the hole on your recoil booster too big, i think it would short stroke, or not unlock the bolt from the barrel at all.

ill dig up some parts pictures for you as soon as i can. hopefully i can get some decent pics.
 
1340 said:
I have my recoil booster drilled to .450".
I lubed everything up really well before shooting so there would be less friction.
I was shooting surplus ammo, which like you said is hot.
I have some other ammo I can try.
Also, Irunguns has the .308 conversion listed for $750 US.
I pulled the trigger and ordered a kit.
Click to expand...

The 308 conversion is a great kit!
when you install it do not use the super small booster cone that it comes with, use the 9mm one that came with your gun it works perfect, hopefully you have a spare booster. The one you drilled out may even work its worth a try
Also the Austrian surplus 308 works fantastic with the 308 conversion.
These guns are unfortunately hard on brass, flattened case mouths and dings in the side are common place.
 
The flash hider has to be tight, it is not designed to be adjustable, if there is play then you will beat up the cone and flash hider assembly.
If you decide you need to file the ejector some be careful as if you take too much off it won't eject the round properly and you will have stoppages
The ejector has to be properly timed, to check the timing have the bolt in the gun but the recoil spring out. Slowly move the bolt back until the bottom edge of the bolt is level with the rear of the ejection port. The ejector needs to be out near its maximum forward throw at this point. You should see it sticking out past the top edge of the bolt
 
To 223762
It certainly isn't short stroking.
I usually screw the flashhider on until it touches, then put the latch in the first loose groove of the hide
To Deathrawt:
Have you tried the Norinco 7.62x51? That's what I have. It was made in the '90s, non-corrosive.
 
hey sorry, i couldn't find the parts yesterday. in the pictures there is two used plates and one NOS. to be honest i cant remember which one was jamming the bolt but both failed to work properly and shouldn't look like they do.

k6MKcTX.jpg


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In the picture below the plate had been sanded down and the ejector was riding on the underside of the plate instead of the face of it.
You can clearly see the thickness difference compared to the NOS plate in the background, especially on the side near the ramp.
qoDo2Ng.jpg
 
1340 said:
To 223762
It certainly isn't short stroking.
I usually screw the flashhider on until it touches, then put the latch in the first loose groove of the hide
To Deathrawt:
Have you tried the Norinco 7.62x51? That's what I have. It was made in the '90s, non-corrosive.
Click to expand...

thats what i do as well.

Norinco 7.62x51 works great but steel cased ammo could be harder on parts. i think i have 500ish rounds through mine with no issues yet.
 
223762
Thanks for the pictures.

The ammo I have is brass cased, non-corrosive, boxer primed. (I think that's what it is!)
 
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I have not tried the norc ammo so can't comment on how it works
All I have used is the Austrian surplus and my own reloads and have had no issues with each. Both are brass cased
 
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