I would have to look at my cleaning kit to see what the solution is, but will probably use a bore-shine or similar solvent to clean the barrel before the next go. Pretty sure I haven't had issues with the crown snagging but good to double check.
I have yet to shoot factory ammo out of this rifle. Could try that, though the reloading procedures used have been pretty meticulous. 300wm loads were loaded for a different rifle about the same time using the same process (same powder measure, press, checking runout, etc). We've loaded two different times with the same bad results...I don't *think* it's in the hand loading procedure. Not saying you're wrong, just clarifying where I'm coming from.
