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TWN Mg34 jaming

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#1 Cryonics

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Posted 02 March 2020 - 01:11 PM

I recently purchased a semi auto TWN MG34 and right from the start she would stove pipe the spent cartridges. I tried just about eveything to fix the issue but to no avail. So far I changed the recoil spring, barrel, bolt assembly, ejector pin and many other parts. I decided to take a high speed video of the problem and it seems to be something really silly and easy to fix. Basically the round is extracted, comes out, bounces off the trigger guard and goes back towards the front of the rifle into the ejection slot and then gets slamed back into the gun by the bolt assembly. It would seem that by adjusting the angle of the trigger guard so that the cartridge would bounce downwards instead of upwards would solve the problem. Unfortunately I tried attaching various things to the trigger guard to adjust the deflection but to no avail. You can see the high speed video at https://www.youtube....h?v=-pTcqz5hdAk

If anyone could look at the video and offer some kind of suggestion as to what might be happening or a possible fix, would be greatly appreciated.


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#2 APEXgunparts

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Posted 02 March 2020 - 01:40 PM

On the OLD MG42.US board I had a thread about the 9.5mm(?) boosters that are delivered on the MG-34 from TNW.
I changed mine over to a standard size and that reduced the speed and violence of the recoil.
I think once the guns get "broke in" they do not need so much energy to operate.
It used to bounce the empties off the bench and hurl them quite a distance downrange til I changed the booster cone out.
ALSO, APEX had some Yugo made canvas brass catchers that hang on the bottom of the MG-34.
Last time I fired my semi (before I sold it) I used that to capture all the empties.

You are not the only owner that had issues with empty casings bouncing back into the gun!

Richard


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#3 peter kohler

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Posted 03 March 2020 - 08:24 AM

I had a problem with my tnw stove piping and not ejecting properly.      my rounds would flip backwards into the chamber or jut kind of fall out  .   I carefully examined every inch of that gun and I found the ejector plate screws were loose.    I removed them both and cleaned the oil etc and put them back in with a bit of locktite.   my mg now spits them out to the front and zero jams.  this is with both live and my two piece blank fire barrel.    my mg fires 308.    I chose this for the caliber for the cheaper blanks and ammo.  btw this past weekend I ran through about 8-9 hundred rounds of the blanks at a reenactment with only one jam.    a member on weapons guild sent me some larger diameter screws to replace the small ones . he did this with his mg when he was building it.  tnw probably should have used the bigger screws to begin with.     this will involve drilling and tapping the holes.    as soon as my machinest buddy has a couple hours we are gonna replace them.   I have a couple extra if you need them

peter


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#4 Cryonics

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Posted 03 March 2020 - 12:06 PM

So are you suggesting I purchase another booster cone?  I thought the ones on the TWN where the same as the auto.  I see two versions on the APEX site, one smaller and one larger opening.  Which would you recommend?

On the OLD MG42.US board I had a thread about the 9.5mm(?) boosters that are delivered on the MG-34 from TNW.
I changed mine over to a standard size and that reduced the speed and violence of the recoil.
I think once the guns get "broke in" they do not need so much energy to operate.
It used to bounce the empties off the bench and hurl them quite a distance downrange til I changed the booster cone out.
ALSO, APEX had some Yugo made canvas brass catchers that hang on the bottom of the MG-34.
Last time I fired my semi (before I sold it) I used that to capture all the empties.

You are not the only owner that had issues with empty casings bouncing back into the gun!

Richard


Edited by Cryonics, 03 March 2020 - 12:18 PM.

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#5 APEXgunparts

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Posted 03 March 2020 - 02:39 PM

So are you suggesting I purchase another booster cone?  I thought the ones on the TWN where the same as the auto.  I see two versions on the APEX site, one smaller and one larger opening.  Which would you recommend?

On the OLD MG42.US board I had a thread about the 9.5mm(?) boosters that are delivered on the MG-34 from TNW.
I changed mine over to a standard size and that reduced the speed and violence of the recoil.
I think once the guns get "broke in" they do not need so much energy to operate.
It used to bounce the empties off the bench and hurl them quite a distance downrange til I changed the booster cone out.
ALSO, APEX had some Yugo made canvas brass catchers that hang on the bottom of the MG-34.
Last time I fired my semi (before I sold it) I used that to capture all the empties.

You are not the only owner that had issues with empty casings bouncing back into the gun!

Richard


I would suggest that you measure the size of the opening in the booster that is installed now, also check the ejector plate in the receiver to ensure it is tight.
I also had an issue with the ejector pin "mushrooming" where it engaged the Ejector plate.

This is the old thread about the booster sizes:
http://www.mg42.us/w...php?f=16&t=3842

 

Richard


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#6 Cryonics

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Posted 02 April 2020 - 05:08 PM

I know it has been a while but life took over my time and only now that we are on lockdown that I was able to try some of the suggestions some of you suggested.  I did get an 11mm booster cone, but unfortunately same problem.  I did try adding the Yugo made brass canvas catchers and unfortunately same problem.  I checked the ejector plate and she is very tight.  I even tried different ejector pins but to no avail.  The only thing I did not try was using larger ejector plate screws as I do not have any and was uncomfortable driling a larger hole into the gun.  At this point I am at a loss of what else to try  :wacko:


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#7 johnsonlmg41

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Posted 03 April 2020 - 06:46 AM

The ejector plate is what you should look into, that and the pin in the bolt.  The pins are very hard, don't wear that much, and as you've said you replaced it so the next option is the plate.   The screws are irrelevant because the plate is keyed into the receiver, so as long as the screws are tight you should be OK.  Upsizing screws is unnecessary unless they are messed up.   It only takes a little wear on the plate to change the pattern.  I've added weld to them, filed them back down and had great results.    

All that said, you're starting with a gun that won't strip and fire the first round, so the whole gun has some issues to start with.  I'm sure even that can be fixed but most guys just end up selling them out of frustration because they don't have the equipment to fix them.  HTH


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#8 APEXgunparts

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Posted 03 April 2020 - 04:29 PM

I am uncertain how an empty case can bounce back into the action when you have a canvas brass catcher attached?

I know mine was quite stiff from age and I had to open it up prior to shooting.

Oh, and open the ejection door before you put the canvas brass catcher on.

 

Now if you are having feed issues, that is a different set of things to look at.

 

Richard
 


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#9 peter kohler

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Posted 04 April 2020 - 08:10 AM

what caliber are you running?    my top cover has the newer style front pawl.   its made to feed better for the 308, but also works really well for the 8mm    BRP sells them    I do have agree with Richard about the the ejector plate or the ejector itself.  I have not changed the screws size in the ejector plate as of yet  as mine is working so well . have you made sure that the muzzle is tight against the cone?  I have the correct muzzle wrench and I make sure its snug and locked in place.   it doesn't take much to do this so don't bear down hard.


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#10 Cryonics

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Posted 06 April 2020 - 12:53 PM

I agree this whole thing is perplexing to me and even watching the video and seeing the case actually bounce back up and into the receiver makes no sense to me.  Has anyone tried redesigning the triger guard so that when the casing hits it the casing bounces down rather than up?  I know with the canvas brass catcher attached the shape on the rear side of the catcher is curved making the casing actually bounce up.  If it were a triangle shape angled down maybe we could get the casing to bounce down?

I am uncertain how an empty case can bounce back into the action when you have a canvas brass catcher attached?

I know mine was quite stiff from age and I had to open it up prior to shooting.

Oh, and open the ejection door before you put the canvas brass catcher on.

 

Now if you are having feed issues, that is a different set of things to look at.

 

Richard
 


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#11 Cryonics

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Posted 06 April 2020 - 12:58 PM

I am running 8mm mauser.  The PPU ammo almost jams instantly on the first shot. I tried some russian ammo that jams probably every 3rd of 4th shot and some romanian ammo that jams every 7 or 8 shots.  So ammo has made some difference but still makes it unusable with the casings stove piping.  Another concern of mine is that I have the spent casing in the barrel upside down and then a bullet trying to enter the barrel and gets stuck half way in.  In some cases that top part of the bolt got very close to the firing pin.  Has anyone heard of people having this issue having a round actually go off while the other casing was in the barrel.  I can see a huge catastrophe with that scenario.

what caliber are you running?    my top cover has the newer style front pawl.   its made to feed better for the 308, but also works really well for the 8mm    BRP sells them    I do have agree with Richard about the the ejector plate or the ejector itself.  I have not changed the screws size in the ejector plate as of yet  as mine is working so well . have you made sure that the muzzle is tight against the cone?  I have the correct muzzle wrench and I make sure its snug and locked in place.   it doesn't take much to do this so don't bear down hard.


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#12 APEXgunparts

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Posted 06 April 2020 - 03:52 PM

Well, a new mainspring and a new recuperator spring would not hurt.
The recuperator spring and pin are captured in the receiver and are often overlooked.

If your gun is really that "drag free" perhaps you need a booster with an even larger opening?

 

Richard


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#13 Cryonics

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Posted 07 April 2020 - 01:46 PM

I did try 3 different main springs but no difference.  I did not try a different recuperator spring but I do have a spare so can try that.  I was also wondering about making an even larger 11mm booster hole but did not know if that would be prudent or done before.  The gun is quite drag free as I do use the recommended TW-25B grease that TWN recommends.

Well, a new mainspring and a new recuperator spring would not hurt.
The recuperator spring and pin are captured in the receiver and are often overlooked.

If your gun is really that "drag free" perhaps you need a booster with an even larger opening?

 

Richard


Edited by Cryonics, 07 April 2020 - 01:48 PM.

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#14 APEXgunparts

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Posted 07 April 2020 - 03:08 PM

I did try 3 different main springs but no difference.  I did not try a different recuperator spring but I do have a spare so can try that.  I was also wondering about making an even larger 11mm booster hole but did not know if that would be prudent or done before.  The gun is quite drag free as I do use the recommended TW-25B grease that TWN recommends.

Well, a new mainspring and a new recuperator spring would not hurt.
The recuperator spring and pin are captured in the receiver and are often overlooked.

If your gun is really that "drag free" perhaps you need a booster with an even larger opening?

 

Richard


BRP can help you with an enlarged booster cone (call to see if he will run one for you):

https://www.brpguns....cone-slow-fire/

 

And a repcuperator pin and spring:

https://www.brpguns....r-Assembly.html

I noted that Brian says loosening the booster cone can also reduce the gas pressure.
I know another gent who was able to get his MG34 running properly by replacing the recuperator pin and spring.

Richard


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#15 johnsonlmg41

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Posted 07 April 2020 - 07:49 PM

neither the booster, nor the recouperator spring is going to fix your problem, but give it a shot anyhow since you'll learn a little bit more about the gun.  Other than items mentioned previously that you probably didn't fix, there still is a good possibility the gun is built poorly and will never run without serious gunsmithing.  There is a reason these change hands somewhat frequently or end up as static displays.....like a lot of other "semi" conversions.  Transferable correct MG34's are often difficult for most collectors to master operations, the semi build is at least 3 levels below that for overall function and design. 

Grease is not a substitute to overcome poor manufacturing or a bad design.  HTH


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#16 peter kohler

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Posted 08 June 2020 - 07:46 AM

so any good news?


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