Conversion parts needed. The new hopper side, and support bracket.
First mark the edge of the part to be removed (old hopper side) to use as reference.
Next using either a spot weld cutter or what I used, a #10 drill bit. Drill out the spot weld just enough to weaken it. Do not drill all the way through the bottom layer,however you may have to drill into the bottom layer a bit to weaken the weld.
Next put the support bracket into place and mark. This will act as a guide where to cut.
Make the 2 preliminary cuts as shown below. These are just to get the old hopper side removed for now.
Should look something like this (without the holes) You may have to grind down the the old spot welds smooth.
Next install the new hopper. The detailed picture below is how it should look. Keep it tight as it will help hold the hopper in place.
Use the lines we marked in step two to line up the new hopper with where the old hopper was. This will get you close. The hopper opening should be somewhere around 3.200". I used a #40 drill bit and aviation cleco temp. fasteners.
Now flip upside down, put into vise and mark the final outline of the support bracket.
cut out as shown below. Do not cut through second layer as shown in the picture on the left side. This will give you something to attach the bracket to.
The conversion parts look pretty neat but are not necessary for the conversion, at least if you have some metal working skills. Removal of the original back plate is pretty much as shown in the tutorial, ie drill out the spotwelds and knock the backplate off. Then take a strip of .035" steel 5/16" wide and bend it to the shape of the hopper on each side where the backplate was attached. Weld it in place to the hopper and another piece will be needed for the bottom plate on each side of the slot. You can clamp the straight strip to the edge of the hopper and weld a small spot on each side of the vicegrip or clamp, then remove the clamp, bend the strip to line it up with the next spots to be welded and clamp again, weld again etc. Basically a bend as you weld deal if you find it difficult to bend the parts freehand. Once this is done replace the backplate, now 5/16" further back than it was before and reweld through the holes left by the drilled out spotwelds. Check along the way with a round or two of 8mm heavy ball to make sure the length is correct. The ammo does not need to fit snug in the hopper but shouldn't have too much room to flop around either. For some this is the simplest solution as it is possible to get strips of steel sheared up the proper width or maybe even to find steel strip in the correct width. MSC and McMaster Carr sell low carbon steel strip in packages with various widths and thicknesses and I've seen the same available at many steel supplys and machinetool sellers all over the US.
In addition, If you intend to load both .308 and 8mm you will need a spacer to hold the .308 more tightly as it will tend to jumble up and jam the works if you just fill the 8mm sized hopper. I used a piece of 1/4" thick aluminum cut the the shape of the rear plate for this purpose but you could just as easily use a piece of plastic or wood. It has to go down inside the slot as deep as it can without interfering with the pusher. If you don't cover that area then the .308 rounds will work their way back into that open area and once again jam up the works. The taper on the .308 is different than the 8mm and that is part of the problem with this jam-up thing.
Check with RTG Parts in Peoria Arizona, Robert Johnson had them posted on Sturmgewehr for $149 last week. These are the MG3 loaders just waiting to be converted to load 8mm. The only complaint I've got with the conversion is that the hopper will no longer fit in the ammo can with the loader. Hope that helps Frank
I couldn't fit mine in an 8mm can because the hopper was too wide to fit in the only way that left room for the loader. The original German WWII loaders didn't look like these. They used the GF34 which is much different or the GF41 that was spring loaded and much smaller. The MG3 loader was a later development so its just enough different to not fit....at least I couldn't get it to fit. You may have better luck
The GF34 was actually a pretty complex loader with a lot of machined parts inside. The indexing device pushes the just filled link over one, drops down from under the belt, moves over to the next set of links than pops up again to push the newly filled link over one. It also uses a pretty elaborate "C" clamp to attach it to a bench for loading. The newer MG3 loaders are almost all stamped sheet metal with a "Star" wheel to index and hold the belt in place where the GF34 had a spring loaded plate to keep the belt against the indexing device. With the "star" wheel it is very simple to link up the belts without holding them together or trying to shove a live round in to hold the tab in place so yet another improvement. It is not obvious however unless you see the two loaders sitting side by side how different they really are. On the other hand though, I've seen a few GF34's with hoppers that have either had spacers welded into the hopper or had the hoppers shortened to load .308 so you aren't far off. I'd probably not know any of this if I didn't collect loaders.....