I have two Browning BPSs, a 20 ga. I purchased new about 7 years ago and a BPS Trap ,which I purchased last year. The 20ga I use for skeet and hunting and the Trap model for trap and skeet. The problem if it is one, is the barrel on the 12 ga.Trap model always has lot of rust on the patch when I clean it, which I do after every use. The only thing out get from the 20ga is carbon and plastic. I wondered if Browning used older barrels on the Trap models. The the barrel is stamped" 2 3/4" Field Model "it has the Invector Plus tubes. I never got rust out of the 20 ga which I use the same cleaning procedure. Any ideas?