Alas, not a project..... I buy and sell some gun parts on occasion.
A few months ago, I got a bunch of parts from a guy who used to do work for a police dept. He would do the work on their duty guns and in exchange, they would let him cut the receivers on the evidence guns and he got to keep the rest of the parts. This barrel happened to be in that lot. I probably received some of the other parts but already sold them off not even knowing what they might have been for. My loss, as it seems these parts are quite costly from the quick search I did after it was ID'd.