I sent a picture to FA and the gun itself and they said it was the forcing cone. Right at the beginning of the barrel where the bullet jumps from the cylinder to enter the barrel used to be a smooth ring. Now the inside of that ring is jagged and looks eroded. Don't know what else to say. I've had the gun for many years, but there have been stretches where I haven't shot it for multiple years. My load with the XTPMags are 300 gr xtpmag and 27 gr W296. The 240 gr xtpmag is loaded with 36 gr W296. I thought this was hot enough, but maybe I'm not using enough powder.
I'm not trying to blame anyone here and certainly FA has been very good to work with. I'm just trying to see if anyone else has had similar problem.