PBB semi mg34 build

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panaceabeachbum
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PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 6:57 am

Thought I would share some misc pics of my 34 semi build, these are in no paticular order. Many thanks to Orin for getting me up to speed on exactly how/why the transferbar/disconnector works. Richard

these bolt pics are a mostly of the old style sear, somewhere mid way thru machining the old style parts I caught wind of the lighter trigg pull version and machined the newer sear and sear holder.

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 6:59 am

this shot shows the cut that must be made in the bolt body to allow the sear assembly to fit in place

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this shot shows the relation ship of the sear and its holder to the other parts of the bolt

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:00 am

more shots of the bolt

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:05 am

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this shot shows the relationship of the trip lever and bolt when all assembled in the rifle

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:07 am

here are a couple of shots of how the nose of the trip lever rotates reaward when the bolt opens to act as the disconnector

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:11 am

this shot shows the area on the inside of the rec scrap that must be filled BEFORE rejoining any of the pieces to prevent an unmodified FA bolt from being inserted into the rec.

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:13 am

here is the area on the outside of the reciever that must be filled to prevent the introduction of a FA sear into the receiver. Its very important that this area and the one pointed out above be filled with weld before the rec scrap is rejoined to insure that at no point you have been in possesion of an NFA restricted full auto receiver.


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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:18 am

this shot shows a completed semi auto rec and a bunch of scrap on a mandrell to help point out the area on the outside to be filled. The inside of the lower rec scrap has been filled with a large pool of weld just abof the large cross pin before it was slipped onto the jig

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:19 am

Image

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hope some of this helps

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Re: PBB semi mg34 build

Postby tomcatshaas » Thu Jul 26, 2007 7:23 am

This is excellent Richard ! This will help alot and answer many questions folks have had here.

Will you be offering 34 bolt mod conversion services to members here? I hope so.

thanks again,

TC :mrgreen:

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 7:43 am

well I posted all these pics with the thought :( that I would be able to go back and edit/add text to each of these pictures at will so they would make more sense. Had I known the edit feature no longer existed i would have been a little more careful in giving descriptions of exactly what was going on in each picture. I guess I will just lump all the text in a couple of paragraphs below and hopefully it will make sense.Anyway if you have any questions or need a better shot of whats going on in any of these feel free to ask.
Hopefully these will help give everybody an understanding of what makes the semi 34 work. Not a tutorial but other than what filler rod was used or the mechanics of reassembling the other parts there isnt much else to the 34 semi build.

On the rewelding of the rec scrap, I used an aluminum bar to fill the bolt channel and a brass rod to fill the recoup hole. I had to pull one of the cams out to get the rod in the reoup hole, not a big deal to rivet back in place. In addition to the aluminum bar in the center of the rec scrap I used a 2" sq steel bar as the main component of my jig . The bar in the bolt channel doesnt have a large enough cross secton to even begin to keep the rec from distorting during welding so i relyed on it soley to keep the weld material from flowing into the bolt channel. The two inch sq steel bar was cut to fit on the flat top side of the rec where the topcover would normaly lay and a series of large welding clamps were used to pull the rec down tight against the bar. I also used a piece of 1"x2" steel bar clamped to the side of the rec opposite from where I was welding.
I did not get in any rush to weld , used a miller 250 amp mig with mild steel wire (70.000psi tensile) and welded a number of passes to fill the gaps. One of the gaps was aprox 3/4" wide. I just welded on each side of the gap until it was small enough to fuse both sides together. Most of the small gaps required 3-4 passes each to weld the large one took at least a dozen. When welding a project like this its best to weld a small pass on one side, wait for it to cool, flip it over and weld a small pass on the other side and repeat as neccesary. Since I used the 2" sq bar on top and a smaller one on the side opposite welding I must have clamped and reclamped 50+ times during the process. One of the big advantages of welding small passes and allowing complete cooling then reclamping between passes is you can tell exactly which weld/area creates any distortion as you go and can correct it at that point.
Patience is the other big key, I did the rewweld in the top pic over the course of an 8 hour day while I did other stuff, allowing plenty of time for it to cool between every pass. In reality the actual weld time was probably about 20 minutes , probably 2 hours spent on all the various clampig and reclamping procedures and 5+ hours allowing it to cool between passes.
My method isnt as easy breezy as some of the other welding jigs pictured and the constant reclamping was a pain but the upsides are that I was able to use stuff I had laying around the shop and my rec came out almost perfectly straight. No grinding broaching or other fixes needed to get the bolt to drop in, just cleaned up the insides of each weld with the die grinder and dropped the bolt with sear nothc removed straight thru.
Richard

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Re: PBB semi mg34 build

Postby panaceabeachbum » Thu Jul 26, 2007 9:06 am

forgot to mention, I also placed a chunk of aluminum in the ejection port to keep the pieces of rec scrap aligned and avoid to much weld building up in that area also. Copper would be a much better choice of filler material for the eport and bolt channel but the alum seemed to hold up very well.

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Re: PBB semi mg34 build

Postby Bil » Thu Jul 26, 2007 6:46 pm

PBB-thank you very much for the info-it looks like a real nice project.If we can get someone that does the semi mods to the bolt and FCG,there are a lot of 34s that could get built! ---bil
"I dream of a world where I can buy alcohol,tobacco and firearms from the same drive-up window,and use them all on the way home from work!" Dogbert

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Re: PBB semi mg34 build

Postby MauserMatt » Fri Jul 27, 2007 8:03 pm

Bil wrote:PBB-thank you very much for the info-it looks like a real nice project.If we can get someone that does the semi mods to the bolt and FCG,there are a lot of 34s that could get built! ---bil


Yep, that would be true of mine.
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Re: PBB semi mg34 build

Postby Sisu » Sat Jul 28, 2007 12:38 am

Me too, I just ordered a TNW receiver from the Weaponeer GB and will need help with the semi mods.

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Re: PBB semi mg34 build

Postby panaceabeachbum » Sun Aug 12, 2007 5:48 pm

TNW has a patent on this paticular method of semi conversion and I in no way plan to cross any moral, ethical or legal line by offering their design for sale. All the parts shown here were machined for my own personal use.
I believe a couple of other members here offers semi bolt and component services .

I wanted to post these pics and some brief rambling for folks working on their 34 semi builds simply so you can have an idea of how it works and more importantly to point out the areas to be welded up before begining the process of rejoining any of the demilled rec scrap. I think its important to point out the area inside the rec that needs to be filled since it was neglected in another build tutorial and is the most important step in the entire build. Neglecting to fill this area as in the other thread would be considered building an illegal MG receiver since the FA bolt could be droped right in and the gun made to run thru an entire belt simply by dropping the bolt via the charging handle on a loaded belt. Yes blocking the FA sear is important but that step alone does nothing to prevent the gun from firing full auto , its the prevention of insertion of the full auto bolt that will prevent the gun from bieng fired full auto, blocking the insertion of the full auto sear is neccesary but pales in comparrison to blocking the FA bolt that is actualy responsible for the gun going bang.
Apologies for bieng coarse in my delivery of this message but I would hate to see someone neglect a most important area and be prosecuted for illegal possesion of a mg and in turn the site come under fire for aiding in the production of an illegal mg after following a "tutorial" that neglects such an important step. all nfa batfe rulles apply , for informational and entertainment purposes only etc etc .


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