Compensator for HK USP?

Hello everyone. I have three questions:

1) HK currently has a production USP called the HK USP Match. It features a compensator attachment that "looks" like it attaches to the accessory rail. Question: is the barrel "actually" longer than the slide and is "inside" the compensator/expansion chamber? If so, is it threaded in there like regular compensators? I was watching a video of the USP Match in action and when the last round was fired, the slide locked back. The barrel tipped, like it suppose to, but since the compensator is attached to the accessory rail, the compensator did "not" tip. This would leave me to assume that the barrel is not threaded or attached in any way to the compensator. Can anyone who has actually seen this gun give me some feedback?

2) I seem to remember that the compensator, for a short time, was sold as an accessory... was this true? Can it be purchased separately? If so, does anyone have one out there?

3) Besides this compensator, does anyone else make a compensated replacement barrel for the USP?

Thanks in advance to anyone who replies!

James