Well, I ended up buying a CP33 recently. I have only had it to the range once so far, with a Dead Air Mask. I shot CCI target though it. I was at an indoor range, so I can't add much data about loudness, other than it seemed good? I will say it was an absolute riot to shoot! The mags loaded easier than expected, but my thumbs were still sore after a few hundred rounds.
One thing I did notice, was that my pistol is reluctant to feed the first round from the mag. Neither slingshotting it, or hitting the "slide release" (more of a charging handle on this thing really) were reliable. Putting a lowly federal bulk lead bullet round on top seemed to help. Once firing it never missed a beat. I attribute most of this to not pre-cleaning it or lubing it and just running it straight from the box. Anyone else with a similar experience.
My buddy thought maybe it needed a slightly stiffer spring.