I wouldn't get rid of the 300 just because of this entrance hole. Just try some other brands of bullets.
People are going to sometime in their hunting career, expereince a bullet failure. Whether its a premium or a cup and core. Read the post, there is always somebody complaining about a bullet failure. You just can't design a bullet that will do all things all the time. Close range high velocity on thin skin, to long range slow velocity big animals. Failures happen.
Just try a few and find one that works well most of the time for you and go hunt.