Chief - I have one of these things and it is accurate as hell but, due to its size it is definetly not CQB friendly. Especially with the LAM and Knights can on it.
The smaller HKs mention in previous posts are good, have rails and some have threaded barrels which helps in two ways, one you can add a can later and two, you get just a tad more accuracy out of them due to an extra 1/2 inch of barrel length.