What I would suggest you to do is to try the gun out when you received it. Note all of the symptoms in detail then post it here or in PBC (Paintball Dojo now) in BM2K/Defiant forum. The problem that most new BM2K/Defiant owner running into is incorrect LPR setting/tunning that causes solonoid leak. Just learn how to adjust the LPR the correct way then everything should be just fine. Go to www.obdo.net
for all BM2K/Defiant related information.
I would suggest you to look into getting your Defiant "vaporized". This work will fix all of the existing problems on your gun, replace all worn out parts and the "VAPOR" work on top of that. It well worth the money. I had it done on both of my BM2K and Defiant. Here is the link to find out more about it: http://www.paintballtrader.com/vapor/