I think the barrel is the trickiest part of this build. If you use a stock Ruger barrel, most are either tapered, or straight like the bull barrel. The tapered barrel is problematic because it's very difficult to hold on to to install. I spent a couple hours making a special tapered barrel wrench to be able to tighten and loosen the stock tapered barrel. The bull barrel is very heavy and would be unbalanced on an aluminum receiver. (as someone in the previous post pointed out). Below are some barrel examples:
CUTTING THE BARREL THREADS AND INSTALLING THE BARREL.
To create the threads on the tube for the barrel it is a two part operation. First you need to open up the 3/4 inch tube bore to about .764 in. diameter and .700 in. deep. A special reamer that I am making will be included with the jig along with a guide to get the reamer and thread straight. (Definitely prefer the aluminum tubes for easier threading).
One thing I don't like about the Ruger .22s and a lot of older guns is the threaded on barrels, the clocking is a big hassle. If using a stock barrel you would first cut the threads, install the barrel tight, carefully line up the sights with the top of the jig, (there is a line on the jig that is at top dead center to help) then drill out the take down hole., remove the barrel, and finish the receiver, then reinstall the barrel during final assembly.
I much prefer a barrel nut design for easy barrel replacement. Below is my current design that seems much easier for us home builders:
Barrel thread reamer
Barrel nut and wrench
Top nut and wrench
The barrel design is very similar to the Ruger Lite and the Pac-LIte in that it has a steel barrel liner inside an aluminum tube, although they are part of the receiver and mine is separate. The jig will have a hole for a pin to index the feed ramp for proper clocking, and an alignment pin will index the barrel cover with the breach. The end of the barrel is threaded for suppressors etc., but if you are in a state like California you can put on the cap nut and pin it pretty easily.
I will have to make two custom wrenches for it, one for the barrel nut and the other for the nut second on the muzzle end that holds the whole assembly together under tension, again similar to the Ruger Lite.
Another nice thing is you can leave the barrel "cover" plain or customize it like some Ruger examples below: