2 piece blank barrle for mg 13

[blckwlfny]

is there any reason why a 2 piece blank barrel wouldn't work in an mg-13?
it would seem to me that moving the weight of the short lower piece instead of the whole barrel would allow the use of weaker blanks...
suggestions anyone?

[Blanksguy]

Post some photos of the parts w/barrel involved and I will be able to see if it can be done or if other "issues" will come into play.

I will need to see barrel and any parts that are attaced to it......along with the bolt-assembly/recoiling-parts and anything attached to them.

Regards, RichardS (Temp. in SA, TX)
US Army, Retired.

[blckwlfny]

ok here are the pics, I tried to get what you need.

the barrels are long and skinny. there is no barrel bearing or booster on the front, the end of the barrel simply sticks out the front of the shroud.

I have a 1 piece barrel adapted for blanks. it uses a restrictor that screws onto the threads used for the flash-hider.

pic of the right side of an unmounted barrel and a mounted one attached to the housing. the entire structure of housing and barrel fits inside the receiver and must recoil about 1/4" to unlock the bolt (it is at the right and is facing the wrong way if the gun was oriented according to the other pieces)

close up of mounted and unmounted barrels showing the interrupted screw setup

this is the receiver with the bolt, barrel and housing removed. The plunger and spring on the lower right perform the same function as the recuperator in the mg 42

1375200388472.jpg (20.72 KiB) Viewed 3377 times

top cover open, barrel is in the rear, unlocked position. the bolt is all the way back. the pencil is on the same piece as it is below

1375199944218.jpg (22.84 KiB) Viewed 3377 times

[Blanksguy]

Thank you for posting the photos.

I have one question at this point........
Does the barrel-assembly with barel-extention stop against the flaired area just in front of the interrupted-screw-threads (?).
(IE: Is this the point that keeps the barrel-assembly from moving forward ?).

Regards, RichardS (Temp in SA, TX).
US Army, Retired.

[blckwlfny]

I am not sure of the actual term, so for clarity,I am calling the "other piece that's not the barrel" in picture 2 the "housing"....
The barrel and the housing are permanently locked together. It is the entire housing/barrel that recoils.
...yes you have to damn near disassemble the gun to change the barrel...I don't know how they did this under fire.
The piece that I indicated with the pencil is a square-shaped tab on the top of the housing. In the second picture you can see this tab from the side. It is rearward of the long oval ejection port about an inch after the housing goes from square to cylindrical.
This tab is kept from moving forward by the receiver itself. Note on the left of the last four pictures, before the top cover hinge, there is a substantial c-shaped piece of metal that this piece rests on and this stops its forward travel.

[oakrodent]

a 2 pc barrel would work just fine in the 13. It would have to be custom made to each 13. The front half of the barrel would have to be welded to the barrel nut on the front of the shroud. The way this gun work it has a barrel that is threaded into the bolt carrier. The carrier in the closed position is up against the front of the receiver. When it is fired, the barrel recoils pushing the bolt carrier back, after a few mm the bolt lock releases and the bolt accelerator accelerates the bolt back to finish ejecting the spent casing. Very thought out and reliable, but over complicated but it does keep the actual receiver very short. The bolt carrier only moves a few centimeters ...not much so yes a two pc barrel will work. I might have a friend who would manufacture the barrel for you. There would have to be a couple of measurements and two barrels used to make it. If you want I will ask him if he wants to take on this project? He is very good at making two pc barrels. It sucks that there might be another 13 out in the field reenacting thou

[blckwlfny]

Oak,
Its already out there...I believe you helped contribute too
Dennis at Midwest Metal did a great job not only on the gun but on creating a 1 piece barrel to reliably fire .308 plastic blanks. they're not very powerful though so I was hoping for a bigger bang with a 2-piece (they're loud as hell in my roller-less '42)

YES please get in touch with him, I would be VERY interested

Ill send you an email so we can work out the details.
Thanks

[Blanksguy]

That was the information that I was loking for.

As long as the barrel w/extention stops against the inside of the receiver against the flair on the rear/outside of the barrel, then it only requires a 2-pcs. Blank-Barrel-Assembly made up very similar to the 2-pcs. Blank-Firing-Barrel-Assemblies that I was making up for the MG42 and MG34.

Have a good machine-shop in your area make up a "piston-end" (with "flair") threaded for your barrel-extension........then have him take a spare MG13 barrel.....cut the threaded end off leaving half of the "flair" at the rear to be used as a stop of the portion of the barrel so that it can't move forward. He will then need to bore the rear of that barrel so that the "piston" will fit into it with .005" - .010" clearance.
Look at the photos in the thread about Blank-Adapting the MG42/SA42.....they should show these areas in detail.
The last part would be to drill/tap the muzzle for 1/2x20 TPI Allen-Plugs that you will need to drill with different size restrictions for operating with different Blanks.

Last.......the machine-shop should be able to make you up a second threaded-piston.........which you will need to chamber one for 8x57mm Blanks and the second to 7.62x51mm/.308 Blanks.

Regards, RichardS (Temp in SA, TX).
US Army, Retired.

[blckwlfny]

There is a problem with using half the flair. The barrel is retained onto the housing with a lever that prevents it from spinning
This lever protrudes through the flair and locks over it. This would prevent the piston end from unlocking

[Blanksguy]

You could make a spare retaining-lever (shorter) for use with the 2-pcs. Blank-Firing-Barrel-Assembly (??)............or build the 2-pcs. Blank-Barrel with a "retaining-screw like the WWII German Blank-Barrel-Assemblies so that it will remain in-line with retining-lever (??)..........photos of these are in "MG34 and MG42" book........then just cut a "keyway" for the retaining lever at the rear.

Regards, RichardS (Temp. in SA, TX).
US Army, Retired.

[blckwlfny]

Thanks. I will check out those pictures.
I looked at the pictures of the mg 42 blank barrel in the other thread
I noticed that the piston end has a stepped down shape.
what would you suggest for a minimum of wall thickness around the battery?
and how longer than the cartridge should the piston
end be?
Thanks

[Blanksguy]

I would suggest about 7.5" OAL (IE: With barel-extension-threads).........and then measure the barrel just in front of the "Flair" for diameter.

Then measure an 8x57mm and .308 case just above the extractor-groove.

Take the barrel-diameter....subtract the largest case diameter...........and this will give you the barrel-meterial that you have left. Half of what is left is used for the piston-diameter.......and the other half is used for the barrel (minus the "running-clearance of .005" - .010").....(IE: The piston-hole size is the piston diameter plus running-clearance.).

Regards, RichardS (Temp. in SA, TX.).
US Army, Retired.

[blckwlfny]

I have been trying to rent a 7.62 reamer and a couple of go/no-go gauges. All I can find are .308 reamers and gauges. I know that there's a slight difference between them. I'm hoping to make this to fit mil-surp blanks including plastic. I assume a looser fit is better....
Do you have any suggestions?
Thanks

[Blanksguy]

Go ahead and use the .308 Win. reamer............. set head-space up on the loose end.

Regards, RichardS (Temp. in SA, TX).
US Army, Retired

[blckwlfny]

Gotcha thanks
Now b/c I'm making a .308 piston end to work with the soft-shouldered plastic blanks, I cannot just re-bore the 8mm chamber....it doesn't leave a sufficient step for plastic.
I will probably be fitting the "flair" with an entirely new chamber in the form of bushing which I will insert into the flair and threads and will comprise all of the section that fits inside the front barrel section.
Does this new chamber piece need to be hardened?

[Blanksguy]

Have you thought about have a "machine-shop" make up two examples of the piston ends.....instead of using two barrels to make up your 2-pcs. blank-barrel-assembly..........(?).....you can have the machinest bore a hole through the entire length of the piston-sections so that you can chamber them........(just a thought.).

Do that and then just use one barrel to make the front part.........saves on the number of barrels needed.

Regards, RichardS (Temp. in SA, TX).
US Army, Retired.

[blckwlfny]

Also noticed....the barrel narrows a LOT between 6.5 and 7.5...not much meat left
Can I get away with a 6.5" piston end?
If I do, should I make relief cuts to lighten it, or do I need a certain amount of mass?
Thanks in advance

[Blanksguy]

If you subtract the length for the piston's threaded-end and half of the "flair" (used to secure the piston).......you should be close to that.

Also......cut grooves as I did to give the carbon a place to go.............and to aid in "stability" so that the moving parts don't have the chance to "cant" and cause a malfunction.

As far as diameter of the piston.......if you used the earlier computation..........what was the thickness of the material left for the barrel-walls at its most narrow point (?).........options would be to shorten the piston .5"......and/or to make is slightly more narrow (?).

Regards, RichardS (Temp. in SA, TX.).
US Army, Retired.

[blckwlfny]

Thanks Richard
I had considered machining a whole new piece, but the cost was significantly more as the lip must be hardened to withstand the pounding against the forward piece.
To answer your other ques: The wall thickness is .149 at 6.5" length, the barrel narrows to allow a wall thickness of .098" at 7.5" length a wall thickness of .074 is all that can be allowed.
Would you recommend stepping it down or tapering it? If so, how much?
Thanks

[Blanksguy]

I would do a few things....
1: First....I would make up a drawling of what you want the piston-section to look like.......making the piston slightly smaller in diameter.........with a length of 6.5" in front of the "flaired/threaded end............then:

2: Take it to a machine-shop and ask for a quote to make 4-6 of the piston-sections out of a good grade of steel (I don't have the information for type of steel as I never asked my machine-shop-guy what.....just told him that it would need to be machineable.....not to rust easily......and hard enough to do a lot of pounding as it moves back-and-forth)..... You need to have at least 4-6 made to get some discount. Then advertise the leftover pistons for sale here and on the WWII and WWI Reenactors web-pages to get some of your money back.

3: Make the piston straight....no tappers.

4: After the pistons are made.....have the same machine-shop do the barrel. Cut off everything to the rear and half of the flaired-section......then bore it to allowthe piston to enter with .005"-.010" for additional running clearance. Have them cut off the threaded rear-end to save for use to match up the piston-threads.........and do it as one "work-order" to get a cheaper price.

Regards, RichardS (Temp. in SA, TX.).
US Army, Retired.