Sorry to hear about the problems. Thanks for Cabela's, love their service.
I love my KRB. I started shooting 100 grains loose 777 with a 240 gr. Hornady XTP and green sabot. My accuracy was fairly reasonable, however the crud ring build up was horrendous, worse than anything I had experienced in my prior in-line the Knight Am. Knight with 209 conversion kit.
I shoot Pyrodex RS loose in my traditional T/C Renegade, but I bought the KRB to extend my range so I next tried Blackhorn 209. What I found was that the load had to be tight over the charge to assure consistent ignition. Anything less than a tight fit sabot seated hard on the charge was going to miss or hang fire. I am shooting Winchester W209 Primers and want to experiment with the CCI Magnums but they have been hard to find locally. Regardless however, with a 110gr BH209 charge and the 240gr/green sabot load I am experiencing SubMOA groups and it goes bang every time. Perhaps the law of averages catches me at the wrong time and I sure wish we could get a BH209 modified breech plug for the KRB but I am sticking with this combination.
As for cleaning the breech area, the primer residue is a PITA. Windex and aerosol Brake Cleaner along with a tooth brush gets it. Too many nooks and crannies in that area in my opinion. Good luck with your KRB.