Any idea who made this? It's nickel plated brass, has a single row of spiral porting, and scallop milling at the tip. The rear of the barrel, where it threads into the marker body has an aluminum section press-fit onto the outside of the barrel body. The cocker threads are cut into this sleeve.
It came of off an older tricked out mini cocker with almost every upgrade you could get prior to 2000.
Pics of the barrel:
Could it be a PPS barrel?
Here's a pic of the mini-cocker: