It may have be carbon in the throat of the rifle. Carbon can sometimes build up in the area just in front of the case. I’ve found that it takes sometime for the carbon to soften up in front of the throat with most solvents. I now use jb bore cleaner to take care of the carbon in the throat.( works well for that along with jacket fouling ) . It works fast .Ive also heard that Ballistol works good for throat maintenance, but I cannot confirm that personally.
It seems some powders are worse than other for carbon build up.
There is no big trick to bedding a vanguard. In fact they are easier than most to bed properly.
You definitely don’t have enough clearance between the barrel and pressure point. That or you need some pressure on the barrel. Sounds like you are in between with clearance right now. I am talking about the RC.
