Have you loaded for this rifle before? Yes

Does a sized, but not loaded piece of brass do the same thing? Yes

Was the brass new, once fired, fired in your rifle, or fired in some other rifle? Once fired in my rifle

Have you checked your over all length of your loaded rounds? Yes, they are correct or even just under

Have you tried marking up a loaded round with a sharpie marker and chamber it to see where it's rubbing at? Yes it looks like the shoulder just slightly

Is this a factory stock rifle? Or has the barrel been swapped? Stock