Not even finished, but the end is in sight.
I found out one thing in the initial test-firing. I need that hammer-mounted shell deflector ASAP. Because the combination of tapered shells and what I suspect is a higher-efficiency gas system is driving those bad boys out FAST AS HELL. Instead of gently bouncing off my goatee (full-house 357!) they're now slamming me in the cheek.
That's OK - with the short shells there's a ton of room to build the deflector.
BIG shout-out to Xerocraft in Tucson - basically a "rent a complete mad scientist's lair" Hackerspace with machine shop:
Best $40/mo you can spend. I was able to turn that whole gas-trap/front sight base from scratch on a 1953 Logan lathe from cold-rolled steel, and then mill the channels I needed on an actual mill. The barrel nut is carved from a section of 7/8ths bolt as that needs to be harder.