PaulN/KS said:JD,
Nothing really much has changed as this gun has never been a very good shooting rifle.The weather was colder that day which may have been a factor since she uses the yellow lube.
Cold weather and the yellow miracle lube don't mix. Wax based lubes are best for hunting, but a liquid lube is usually better for woodswalks, or line shooting, especially in cold weather.
I would suggest scrubbing the bore with a bronze brush and a good solvent to remove any wax residue, then try a liquid lube, and later a thicker patch of tighter weave. As others have suggested, a larger ball might be in order too.
Many swear by Lehigh Valley Lube, but many home made lubes work well too. Windshieled wiper fluid, Ballsitol/water, soap/water/alcohol, spit, and a number of other home made concotions also work very well, depending on the gun.
Change one thing at a time, and continue to experiment. Eventually you will find a combination that this gun likes.
Based on what has been described, I seriously doubt that the barrel is, in some way, defective.
J.D.