Well this is a long shot...a guess...but worth trying...
There is the possibility that someone broke a shell off at the neck...so you would have a ring of brass in the throat that is nearly impossible to see. I have done that with my 7mm TCU before. Here's what you do to see if it is the problem, and remedy the situation. Take an old .45 caliber or 50 caliber bronze bore brush...if you dont have one, go down to the store and get a new one, they are cheap. Remove the barrel, it is easier. Make sure that the shank part of the bore brush is smaller than the bore, but the brush part is significantly larger. FORCE that S.O.B. down the MUZZLE end of the barrel, NOT THE CHAMBER, until it goes through the other end. If I am right...you will have a 3/8" ring of brass pop out on your brush. If not....take it to your local Gunsmith, but this might be all you need and you will be happily shooting.............
There is the possibility that someone broke a shell off at the neck...so you would have a ring of brass in the throat that is nearly impossible to see. I have done that with my 7mm TCU before. Here's what you do to see if it is the problem, and remedy the situation. Take an old .45 caliber or 50 caliber bronze bore brush...if you dont have one, go down to the store and get a new one, they are cheap. Remove the barrel, it is easier. Make sure that the shank part of the bore brush is smaller than the bore, but the brush part is significantly larger. FORCE that S.O.B. down the MUZZLE end of the barrel, NOT THE CHAMBER, until it goes through the other end. If I am right...you will have a 3/8" ring of brass pop out on your brush. If not....take it to your local Gunsmith, but this might be all you need and you will be happily shooting.............