If you really want to drive your eyeballs batty, check out all the pics in this thread: http://tdh.prop-planet.com/viewtopic.php?topic=1463&forum=5.
In some of the pics, it looks like it's clamped to the MPP, but in a few others, I'd swear the spacing looks different from the front end of the gun, and it looks like there is Webley barrel under the clamp. Of course, I'm getting old now, and my eyes aren't as good as they once were. :cry