Is this a brand new rifle and new factory ammo ? Which Vanguard the synthetic, S2 , etc. ? Model Nikon and rings bases ? Please be specific and maybe one us us can narrow things down a bit. Brass shaving on the bolt and bolt resistance leads me in the direction of re-loads or action binding ?
Without any info I'm going to take a guess. Re-loads, bedding or action binding , I doubt it's the scope since you changed it. Very dirty chamber.
How does factory ammo chamber and extract ?