It's not normal but it happens, and yes it's most likely caused from the Loading Jag on your Ram Rod. It happens when you have a Fouled Barrel that is really fouled and you have to really push hard to get your next load in. The Ram Rod Bends and Forces the Jag into the side of the Barrel causing the Scratches. They make a Loading Jag for this porpouse that helps keep it straight going down the barrle.
It's hard to say one way or the other if the scratches will effect accuracy, bad scratches will let the powder blow by them causing different results, others wont be noticed. If your ML is still shooting fine dont worry about them, if it starts to shoot bad then you'll know why.
Also some Barrels are better than others, all steel is not created equal. some can take the abuse and other's not. I noticed this on one of My Cheaper MLer Barels, but have not seen the effects of this on My Better SS Barrels. The one with Scratches did Not Effect the Accuracy.
(BP)