The 4x12x40 leupold will work fine although it would not be my first choice.To break in a barrel,I clean after every shot for ten shots then after every three shots for another fifteen.I then clean after every 12 to 15 rounds with high velocity cartridges.I load and shoot only full power loads in my ultramags in order to keep familiar with the trajectory.I have many rifles so I spread out my practising over several rifles.