I rethreaded the breech to fit an AR barrel extension. If one is very careful, this can be done without using a reamer to adjust headspace. I missed by .003, took a few turns by hand with the reamer to set the headspace.
In the gas block area, the barrel was too small for the gas block. Bored a piece of aluminum, drove it onto the barrel. Turned it to fit the gas block. Installed the index pin in the extension, put the barrel in the upper, and located top dead center for the gas port location. Located the port position lengthwise. Drilled the gas port. Threaded the muzzle for a brake. Installed the barrel with a barrel nut and float tube.
Left the barrel at 22". Being a fairly slender sporting barrel, balance is good. Shoots quite well.
Very cost effective way to barrel an AR if one does the work.