WAAAYYYY too little break in, and probably done wrong. When I got my Armalite AR-10T Flat Top, there were two sets of instructions on how to break in a Match Grade Stainless barrel. Method #1 was to shoot one round, cleand and burnish with JB Bore paste (20 strokes, no less!) to clean and polish, repeat 5 times, and then go to 3 shots between cleanings for the first 20, and then 5 shots for the last 30 rounds. This would be at least a 4 hour job, if not more.
Method#2: Fire a moly coated bullet down the bore, clean with dry patch and repeat 50 times. That's it! Needless to say, neither my AR-10 or my .338 have EVER had a bare copper bullet shot through them from day one. CLEANING is not the only reason to break in a gun, and in fact it's not the major reason. The real reason is to smooth down all the microscopic imperfections in the bore, and it's significant that David Tubb himself came up with a set of microfine abrasive bullets in 5 grades to accomplish this exact purpose.
Hope you read this before you wind up going down the wrong track.