Semi Auto MG34 project
The goal is to turn this pile of scrap into a semi Auto MG34. The parts are from 3 different receivers. There is overlap on some of the parts, these will be cut and milled square for welding. The extra sections will be used as fillers where there is a big gap between sections. The gaps are to big to just fill in with weld, since the receiver is a precision machined part shrinkage and warping will be to great.
Strength is not to much of an issue as the bolt locks up into the barrel, however it needs to be straight and precise as all the parts fit closely. The receiver seems to be made from ductile Iron. I have done some welding tests on scrap pieces and found a mild stainless alloy rod works well. Using a post black will hide the welds.
The first step is to make a jig to hold the parts securely and in perfect alignment. The top plate of the jig will set the inside length of the receiver from front to back.
Questions and comments can be posted here.
The next step was to select the setions that will be used for the receiver and those for fillers. The parts were blasted to remove all the crud and the center section was cut and milled square.
This section needs to have some areas where the full auto sear parts go filled in to make it legal. This is the area shown in the white box, a bolt block needs to extend into the bolt sear slot inside. This needs to be done BEFORE any other work is done.
Filler blocks were made from CRS and the edges beveled, then the parts were welded in with heavy penetrating welds. When this was done the welds were ground so that the grip will seat on the section, as the grip pins will be used to locate the forward sections. Once this was done the parts were mounted in the jig, and tacked in place. After tacking the parts were welded. the next step will be to locate the front section and make the fillers.
I got the rear section fitted, both parts were cut at an angle and were a bitch to cut and fit tight and square. I used the rear stock latch as a guide. once the parts were fitted I jigged them up and tacked tham in place. with the rear section in place I was able to locate the front section. the top bar of the jig sets the proper overall length. with the correct length set I cut and fit the filler for the left front side and tacked it in place. when I was satisfied it was all square I welded the front and rear in place. after the thing cooled down I removed it from the jig to see if it was straight. It is, so I ground down the welds to see where more metal is needed and to test fit some of the parts. all the parts fit pretty good. the bolt has a tight spot and the retracting handle slot needs some filing. other than that it is all good so far. the next step will be to weld in the last 2 fillers, grind and final fit the parts.
I welded in the last 2 fillers today and ground the exterior. there are a couple of spots that need a little more weld. All the parts fit good except for the bolt that is binding a little. I need to weld an extension onto a file to clean out a couple of spots in the bolt channels. other than that all the parts fit properly. There is a hole missing for the barrel jacket retaining plunger that needs to be drilled. other than that it is pretty much finished.
The next step will be to do the bolt and grip mods.