MG42 Troubleshooting

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RetiredBuilder
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MG42 Troubleshooting

Postby RetiredBuilder » Mon Dec 10, 2018 7:53 pm

Hello everyone,

Was wondering if I could pick all your brains for a minute about an issue I have been having with my 42.
Gun/setup details:

Gun: Full Auto German MG42
Caliber: Running MG3 Parts (Top Cover, Booster Cone, Feedtray)
Ammo: Factory Lake City 7.62 XM80 ammo
Belts: German/POF belts
Barrel: Ravenna Armory .308 barrel turned down from 1919a4 barrel.
Headspace: Used gauges to check headspace and passed.
Recuperator Rebuilt by Black River Militaria so it has fresh springs.

This was my first time firing the gun so I don’t have an comparison of firing it in 8mm yet because I am still waiting for some factory yugo 8mm barrels I ordered.

The issue I had two times was the gun fired great for about for about 5-6 rounds then it stripped a round off the belt and stopped halfway into the barrel chamber. Then when I pull on the barrel door latch I knocked the round out as it hit against the trunnion area and just fell out. So its not getting stuck supper tightly.
After examining both the rounds that didn’t chamber fully you can see they are rubbing very significantly to point of creating a raised edge on the side of the case, Im guessing that’s what stopped them from chambering. The rounds that fired did not have this rub mark.

I am trying to isolate the point of where the round is rubbing. Is it while getting stripped off the belts? On the path to the chamber? Trying to enter the chamber?

I was hoping someone here has seen this before and could save me some troubleshooting.

The first belt I fired was new German belt and very tight, and second was a much looser POF belt.

My plan is once I get my 8mm barrels I’ll run that setup and see if the issue continues and go from there.
Thanks for your time!
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JBaum
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Re: MG42 Troubleshooting

Postby JBaum » Mon Dec 10, 2018 10:33 pm

I'm guessing that the rub is only on one side of the brass? If so, it's from getting jammed into the barrel extension. Provided the stripper head on the bolt isn't chipped, that only leaves the possibility of the depressor plate being incorrectly bent.
In the top cover there is a finger (depressor plate) which guides the cartridge down as it comes out of the belt and goes into the chamber. Closing the cover on top of a cartridge with the bolt forward (instead of rearward like is supposed to happen) is a common cause for the depressor plate getting bent (which happens when the bolt is pulled rearward and forces the cartridge upward into the depressor plate, bending it. After that happens, it doesn't guide the cartridge into the chamber at the proper angle.

The specs for making a depressor plate gauge are in the WWII German armorer's repair manual. I've sold out of the gauges I had made from those specs.

I'd start with swapping the top cover with another one to see if that solves the problem. If the problem is gone, then it's the depressor plate. Re-bend it until it matches the good one.
John@German<remove this>Manuals.com

http://www.GermanManuals.com

RetiredBuilder
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Re: MG42 Troubleshooting

Postby RetiredBuilder » Tue Dec 11, 2018 1:28 am

JBaum wrote:I'm guessing that the rub is only on one side of the brass? If so, it's from getting jammed into the barrel extension. Provided the stripper head on the bolt isn't chipped, that only leaves the possibility of the depressor plate being incorrectly bent.
In the top cover there is a finger (depressor plate) which guides the cartridge down as it comes out of the belt and goes into the chamber. Closing the cover on top of a cartridge with the bolt forward (instead of rearward like is supposed to happen) is a common cause for the depressor plate getting bent (which happens when the bolt is pulled rearward and forces the cartridge upward into the depressor plate, bending it. After that happens, it doesn't guide the cartridge into the chamber at the proper angle.

The specs for making a depressor plate gauge are in the WWII German armorer's repair manual. I've sold out of the gauges I had made from those specs.

I'd start with swapping the top cover with another one to see if that solves the problem. If the problem is gone, then it's the depressor plate. Re-bend it until it matches the good one.


Yes, the rub is only on one side. Thank you for the analysis, luckily I have three of your manuals including the German armorer's repair manual so I will check the depressor plates specs in there. I also have another top cover I will try switching out.

Thanks for the help JBaum, owe you one.

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Re: MG42 Troubleshooting

Postby BELinNC » Tue Dec 11, 2018 8:51 pm

If it were mine and it was a WW2 gun I would try it first with all original 8mm parts. See how it performs in stock condition before adding caliber conversion parts. You would have a better starting point to determine what might be going on. What concerns me in your description is the after market barrel. Maybe it is not up to spec. I recently gathered all the parts to mimic an MG3 in my rewelded post dealer sample MG42. It was running fine in 8mm and the conversion works well in 7.62 so far. It took a long time to find a nice MG74 barrel, but it all works great. I think I would at least try a military spec barrel in your gun to rule out the commercial barrel as a suspect. Good luck!


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