Got the barrel fitted, gapped, and pinned in place, and then got the trunnion welded into the receiver.
Cocking tube modifications are going on. I split the bottom of the tube over the trunnion, and replaced it with a thinner shim sheet to keep the interior of the tube at the correct level for the operating rod, and lower the center of the tube down to fit the receiver. It's correctly located now, with 0.020" cocking rod gap. I've got to mill out an aluminum heatsink to fit in the tube, and since I though I'd gotten the op rod stuck in the tube after fitting the thinner sheet, I have to re-make the rivit that holds the stopper block inside the tube.
Protip: That rivit is not what holds the stopper block in. I don't know what does, but it ain't that rivit!
It's been a long time, and I'm still not done. But...
even in its incomplete state, was able to do this:
It has issues feeding from the magazine, and there are some spring tension issues to fix regarding the main recoil spring. I am still working on the front handguard, rear sight assembly, optics rail, bolt hold open, and forward assist.
In the year and half since I last posted, life had some turmoil and I lost my machines at the house. I can't work on firearms at work, so I had to put all this on hold for a bit. I've gotten a new lathe for the house shop, and am about 1/3rd of the way through rebuilding it into a usable machine again. It will be a better, sturdier, more rigid machine than my old lathe, it's just taking me a long time to get back to being able to mess around with this again. Also, I have a new Beretta AR70/90 kit to reverse-engineer parts for. The bolt is made of pure unobtainum, but IF I could find another bolt for it I would make a second barrel to shoot 6.8 as well as 5.56. Seeing as all the kits imported to the US are already sold out, and they were only available for about a week...it might be a while before I find that second bolt.