Needs some help with my .22 Marauder

My Marauder has been spot on since I got in in February but two weeks ago it started shooting all over the place. Cleaned the barrels and checked the barrel band. No dice, the gun still shooting poorly. This morning, I decided to chrony the shots and found it was all over the place. no wonder it was shooting poorly! The readies were 803, 711, 758, 803, 732,780, 743, 810. The breech O ring appears to be intact. I put an e-mail into Crossman.
Any suggestions from Marauder owners?

Doc
 
Something to check is if the hammer is sticking in the tube. All the holes and slots in the air tube are stamped and can have burs that can cause the hammer to be kind of sticky and erratic in operation. One of the things that one should do when doing any tuning is to disassemble the gun and debur the area where the hammer lives with a Dremel tool and polish the hammer and its chamber. I use dry graphite powder lube. I did all this to mine and it really smoothed out the operation of the gun. It even cocks smoother now. I know its scary for some to take their gun apart but its really not hard if you are handy at all. Its a good way to learn the operation of your gun. The Mrod is known as the tinkers gun so tinker away. There is lots of info on all this stuff on Youtube and at http://www.marauderairrifle.com/forum/index.php?sid=fa38df20d91def90f1d381d49c359235