Receiver Welding Process

Receiver Alignment

The receiver, being torch-cut into 4 or 5 parts during the demill process, must be cleaned of the slag in preparation for re-welding.  I used a dremel with a combination of sanding disks and cut-off wheels to remove the slag.

When clean, you must clamp the sections in prep for welding.  This isn't a difficult process, but it is tedious.

I used Pirate's U-channel jig to align the parts.  I couldn't find U-channel at Home Depot, so I bought some of the shelving channel from the hardware aisle.  The 3/8 bolts fit fine.

I have a receiver from Angola Armory, which was a 3-cut receiver (and is in 4 parts).

Rear Cut Alignment

The problem with the U-channel jig is that the rear section can't be clamped down (too small).  I found that using parallels (from my mini-mill accessories) were a convenient material to brace the parts as they were clamped in place.  Here's a tip - have plenty of 3" C-Clamps during this process!

Alignment here is with the top cover (should lock properly) and the camming piece dimple distance (read further).  I dug up a thread on www.mg42.us that indicated the distance should be 15.5". 

Middle Cut Alignment

I was able to figure out the critical alignment.  The camming piece (sometimes referred to as the trunion) is held in place by two matching divots that were stamped into the top and bottom.  I have simply to keep the distance from the rear of the receiver to the dimples the same measurement, and I will know the middle section is aligned top-to-bottom.  The sides can be aligned by clamping in place as above.

15.5 inches.  Wouldn't ya know it, mine measures right up!  :)

Here's the setup I used:

Front Cut Alignment

This is how I got my front cut to align.  I basically clamped a few rigid aluminum tubes to the sides and used a combination of fishing line strung down the centerline, and a steel rod down the barrel, to align the front section.  Yes, the barrel is installed in the alignment process.

After playing with the now-assembled receiver, I'm not sure that this section is as critical as I made it out to be.  My receiver is slightly twisted, and I'm assuming the warp is due to its use/misuse by the original owners.

I spot welded, and then tested to be sure it worked.  I had a misaligned section on the first try, so I had to cut and reweld one time.  It aligned correctly the second time.  "Slow and Steady" is the rule here.