I bought an MCT Airwolf in .22 here in the classified that is probably my favorite rifle. I have a MK4 /177 I bought off the classifieds that also is also shooter and the only difference between the MK4 and an Airwolf CDT/MCT appears to be the bottle.
If you are thinking of buying that pre-owned one on AOA, grab it. You can't beat that price. As cheap as the Turkish and Chinese stuff on the market now.