I had several Hart Barrels most cleaned easy and broke in easy. One 30 Cal was a dream, but another .30 I recently broke in was a bear. The first 10 shots were brutal, severe copper.
As for Broughton, they are the only barrel I'll use at this time. 6.5 broke in easy and my 300 WSM
5-C (175SMK's) Broke in so easy I thought something was wrong. I tried several cleaners because there was so little copper.
To be honest the Hart was shooting a 200 accubond with long surface compared to the 175 SMK so that may contribute to copper alomg with high FPS.