Ive had my Marlin 25N for at least 25 years. Ive put at minimum several thousands of rounds through her and Ive never cleaned the barrel because its always been dead on perfect each and every time through the years. Then a few months ago we had company over to the house and I set it in a different corner out of the way, and I dont know if it got knocked over or if it fell over on its own, and afterwards I didnt know it but apparently when it fell over it jarred the lead build up inside the rifling and later I realized it was starting to shooting erratic. After eliminating my first suspicion of the scope I knew something else was wrong. Anyway I had to clean the bore and of course there was a lot of lead build up but I got her whistle clean but now it doesnt group at all like she use to. I was reluctantly thinking about taking the time to shoot many more rounds to see if my groups might tighten back up ???, and Im not sure if there is a good answer to my question here, or if anyone has had a similar experience, but considering that Ive shot so many rounds through this rifle in years past, then is it possible that the rifling is wore out, and it might not be worth my time or trouble ?