Problems with blank firing MG-34. Your help need!!

Schneider · Post by **Schneider** » Mon Feb 05, 2007 2:10 am

Hi All,

I tray to make blank firing MG-34 on soviet blank cartridges for AK.
I make special barrel with adjustment nut. I tray to fire with nut with hole 3 mm (red mark on pics).
After first cartridge bolt didâ€™t go to back position. As I understood It is not have enough energy.

I would like to herd Your opinion what I need to do:
- make a smaller hole in adjustment nut
- change spring on barrel finger to more flexible (red mark on pics)
- or something else

Thank a lot for You attention and help!

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Post by **JBaum** » Mon Feb 05, 2007 2:53 am

Hello to the Ukraine!

I see the chamber in your barrel doesn't look very smooth. This is very important with the MG34. The cartridge expands when it shoots, and if the chamber isn't very smooth, the shell sticks in the chamber a little. This is all it takes to make the recoil weak.

The bolt and bolt path must be well oiled. The locking rollers on the bolt must turn easily. The spring in your picture must be stiff to make the barrel go forward fast enough. I would not change it. Maybe a weaker recoil spring would help (the big spring behind the bolt).

Does the bolt go to the rear at all? Maybe half way? Maybe it doesn't have enough strength to operate the feeder? Try to shoot when you are pulling on the belt to the right.

I don't know about the 3mm hole, so I will leave that to someone else to comment on.

Post by **DARIVS ARCHITECTVS** » Mon Feb 05, 2007 2:58 am

A combination of two things may need to be done: Reduce the size of the 3mm hole first, and if that does not work, try to reduce the weight of the rear section of the barrel assembly. Weaking the reculperator spring will allow the bolt to unlock, bu there will not be enough force on the bolt to make it travel rearward far enough to chamber the next round.

The real problem is that the AK round is too weak to operate an MG-34. Also, if the powder in the AK cartridge burns too fast, the pressure in the chamber will rise dangeriously high without having enough burn to operate the machinegun's recoil action. THe MG-34 was a precise design to operate using the 8mm cartridge. Changing that cartridge to the 7.62x39 changes a lot of variables, many of which affect each other in complex ways, creating problems that are not easy to solve to make the gun work RELIABLY. Experimentation may be required to get the gun running correctly. Note that it is difficult to detect when the action of a gun is being operated with TOO MUCH force until something BREAKS. Keep that in mind.

Schneider · Post by **Schneider** » Mon Feb 05, 2007 3:34 am

Yes, I got a weak recoil spring. With it is still the same situation + bad chambering....

After firing first cartrige bolt going back (with not full extraction of first cartrige) and try to chamber the second one, it make a jam with two cartriges (first and second).

Schneider · Post by **Schneider** » Mon Feb 05, 2007 8:14 am

jbaum wrote:Hello to the Ukraine!

The spring in your picture must be stiff to make the barrel go forward fast enough. I would not change it.

I mean if I put little bit weaker spring for this barrels pin I could compensate smal energy of AK cartige. The original sprind approved to original weight of original barrel and original cartrige power.
I have think that my barrel did't go to full back position and bolt did't opening correctly...... I dont know...

Here is my project when I start work on it...

Post by **Blanksguy** » Mon Feb 05, 2007 8:19 am

Schneider,
"Blanksguy" here now......

with your MG34 set up to fire 7.62x39mm Blanks....and your bolt is coming back far enough to catch the next Blank, but not to eject the fired Blank......correct (?).

First, a few questions:
1: Did you modify the bolt-face to the smaller diameter of the 7.62x39mm Blank (?)

2: Did you modify the extractor (or place where the extractor sits in the bolt-face (?)...so that it can hold the Blank-rim (?)

3: Did you fit a new ejector-rod in your Bolt so that it will be long enought to eject the fired Blank (?) ....a longer ejector-rod may be required.

4: What belts are you using (?) and how did you modify them for use in the MG34 (?)....what I ask here is that if you are trying to use "RPD" Belts in your MG34, they may be holding the Blanks to hard.

5: How did you modify the MG34 Feed-Tray (?)....photos please of all modifications.

Last.....it sounds like what you have is a 2-parts problem....
1: The bolt is not coming back far enough....make the BFA Hole-Size 2.5mm and try again.....
....."BUT"
2: It may just be your extractor not holding the Fired-Blank well.....or that the ejector-rod is too short......or you may need to odify the face of your Bolt smaller (?)

Semd more photos and information.....but do not change parts just yet till I can see what you have.
I also need to see 3-4 of the fired Blanks to see how the crimp is opening.

Regards, RichardS in MI.
Blanksguy2001@chartermi.net

Schneider · Post by **Schneider** » Mon Feb 05, 2007 9:00 am

Blanksguy wrote:Schneider,
"Blanksguy" here now......

with your MG34 set up to fire 7.62x39mm Blanks....and your bolt is coming back far enough to catch the next Blank, but not to eject the fired Blank......correct (?).

First, a few questions:
1: Did you modify the bolt-face to the smaller diameter of the 7.62x39mm Blank (?)

2: Did you modify the extractor (or place where the extractor sits in the bolt-face (?)...so that it can hold the Blank-rim (?)

3: Did you fit a new ejector-rod in your Bolt so that it will be long enought to eject the fired Blank (?) ....a longer ejector-rod may be required.

4: What belts are you using (?) and how did you modify them for use in the MG34 (?)....what I ask here is that if you are trying to use "RPD" Belts in your MG34, they may be holding the Blanks to hard.

5: How did you modify the MG34 Feed-Tray (?)....photos please of all modifications.

Last.....it sounds like what you have is a 2-parts problem....
1: The bolt is not coming back far enough....make the BFA Hole-Size 2.5mm and try again.....
....."BUT"
2: It may just be your extractor not holding the Fired-Blank well.....or that the ejector-rod is too short......or you may need to odify the face of your Bolt smaller (?)

Semd more photos and information.....but do not change parts just yet till I can see what you have.
I also need to see 3-4 of the fired Blanks to see how the crimp is opening.

Regards, RichardS in MI.
Blanksguy2001@chartermi.net

Hi Blanksguy..

Pics I will make today and put here tomorrow.

answers:
1. No. I did't modify bolt face.
2. I did't modify extractor (In hand operation mode extraction was perfectly and chamber too with original recoil spring.
3. It is still original (I use brand new bolt)
4. I use early original MG belts (I'll make pics) In this belts cartige holds good
5. I have good chambering with original feed tray. Any cartrige jam on feed tray area.

As I sayd before extraction from chamber is Ok, but bolts speed is slow that is way extracted cartrige not put to extraction window...
I try to fire in single fire mode...

Schneider · Post by **Schneider** » Mon Feb 05, 2007 10:13 am

Blanksguy wrote: with your MG34 set up to fire 7.62x39mm Blanks....and your bolt is coming back far enough to catch the next Blank, but not to eject the fired Blank......correct (?).

Yes I fire in single mode and my bolt is coming back far enough to catch the next Blank but not enough to stay in back position!

Post by **Blanksguy** » Mon Feb 05, 2007 11:31 am

Scheider,
Thank you for the additional information.
At this time....I would suggest two things:

1: Change the Blank-Adaptor section so that you can use small "allen-set-screrws" drilled out to different BFA Hole-Sizes/Restrictions....you can do this by drilling the center hole for a "metric-tap"....then only tap it half-way through from the "chamber-side", so that the set-screw do not come loose during firing.
Then....Change the BFA Hole-Size to 2.5-mm and try to fire your 7.62x39mm Blanks again. It will not be loud.......and you may even have to make the BFA Hole-Size/Restriction evn smaller if it does not work....maybe down to 2.0-mm.

2: Do not change the recuporator-spring under the barrel by any more than 2-coils....or 3-coils to make it lighter-weight pushing on the barrel-return. This is the part in your photo that is on the back of the pin in your photo.
NOTE: "IF" you do this, it will need to be changed back to an original spring for firing live 8x57mm ammo. This spring pushes the barrel recuporator-pin forward to return the barrel into "battery" fast to fire live ammo at 900 RPM.....a cut spring would be slower to push the barrel forward and cause problems with live ammo.

3: Remove your Booster-Cup/"Nozzle" under your Flash-Hider as it is not required......and will make firing your Blanks slightly louder.

Also, send the photos and other information on modifications either to the MG42 Board here on this "thread"/subject.....or you can reach me directly by e-mail address at:

Blanksguy2001@chartermi.net

Regards, RichardS in MI, USA.
Blanksguy2001@chartermi.net

Schneider · Post by **Schneider** » Tue Feb 06, 2007 2:43 am

Hi

Yes I have a set of BFA with different hole sizes, but 3mm. it is smallest one. I will make BFA with 2.5 mm.

Esterday, when I make pictures, I found funny problem with my blanks cartriges:
- I have cartriges with two color marks, red and purpul (or something like this)
-cartrige with red marking put to chamber wery difficult, and after extracting cartrige have scraches.
- cartrige with another color marking go to chamber easely and bolt close with it (see pics)

Cartriges is from one manufacturer but different Year of productions.

Now I will start to tune my chamber or make new one.

Also I have idea to cut one compression ring on chamber barrel section, it will be shorter and less weight... ???

Schneider · Post by **Schneider** » Tue Feb 06, 2007 2:47 am

Here is fired cartriges.

Post by **Blanksguy** » Tue Feb 06, 2007 10:03 am

Schneider,
Differnt manufacturers of Blanks in Europe use paint to seal the crimps from water and longer storage. Sometimes the paint changes color a little due to the chemical-reaction to other clear-paint on the outside of the cases. These may be the same loaded Blanks (amount of powder/pressure), but you would have to weight the powder and test the Blanks in your gun (MG34).

On the 7.62x39mm Blanks that will not chamber all the way.....my suggestion is to check the size of your chamber.
Manufacturers make Blanks (ammunition) within a set tollerance....these Blanks may be on the long-side of that tollerance, but still good.
If they were made way too long at the shoulder.....you will have to "re-size" them on a reloading-press with a Full-length Sizing-Die to correct the "head-space".
Before you do this...make sure that the chamber is of the correct size for a "military-rifle-chamber" and head-space for normal 7.62x39mm. Then see which Blanks fit.

....or you could buy a 7.62x39mm Cartridge "Overall-length-gauge"...this "gauge" is like a "chamber" and willl check to see if your Blanks are made/sized correctly.

Keep sending us more information, and send me an e-mail to my e-mail address of:

Blanksguy2001@chartermi.net

Regards, RichardS in MI.
Blanksguy2001@chartermi.net