I welded mine up the other day, did not use much in the way of jigs. I do have a straight, flat table that helped. Also used a good 2' metal ruler.
Most of my work was with a few clamps and small pieces of metal. Also used pieces of copper under the metal.
First I welded the metal block to prevent a FA bolt from ever fitting for use. Mine is located (on the receiver) in the front of the grip stick. I removed the metal "hooks" that are on the front of the grip stick. The block fits inside the grip and acts as a hammer stop. It also extends into the reciever, preventing a bolt with FA trigger ears from ever getting by it. The block is also threaded, so a small (1/4-20) button head allen bolt is used to retain the front of the grip stick
Tack welded parts together, then by eye looked at the alignment. Also checked by feel and with the straight edge.
Tack welded opposite sides, checked alignment.
Got it all together, tacked only.
Took it to the bench to assemble all the parts to see if alignment is correct. This is a good step, as you can cut and reweld if it isn't.
Mearsure overall length. right now its 1/16" short. What to cut to add 1/16"?
Front piece to barrel guard is correct, bipod fits perfect and both bipod mount holes are identical sizes.
Weld under trunnion is correct, as trunnion fits with very little slack in the reciever/trunnion "window".
This means the back weld, for the buttstock, is too close together. Because this is already tacked, it is an easy fix.
Cut one weld with a 4" abrasive wheel, spread it a little, tack it again. Roll it over, do the same thing, cut spread and tack. Check length.
ABOUT THE WELDING WITHOUT FIXTURES
The human eye can be trained to recognize variations to a few thousandths of an inch. This reciever is not that close. Tack it, LOOK AT IT from all sides, bend it, hammer it a little, tack it again. LOOK AT IT AGAIN. LOOK SOME MORE. If you still don't like it, cut it apart and do it again.
Use your fingers to feel for even surfaces (after it cools)
![Shocked :shock:](./images/smilies/icon_eek.gif)
They will tell you if its aligned.
It can be done this way. I will get pix in as I can get to it.
One more thought on welding (I'm using MIG). Tacking introduces minimal heat to the reciever. There is no reason why you cannot do many small welds, letting them completely cool inbetween. This should prevent some of the distortion we so worry about. This thought, in combination with the lack of rigid jigs or fixtures will work as an alternative method for assembling a semi-auto reciever. PS clean all welds and weld areas with a wire brush before welding, to get the most strength from the weld.
OK - lets hear some feedback
![Very Happy :D](./images/smilies/icon_biggrin.gif)