Sammi is just trying to show he is alpha as Mugsy said. Let them work it out as long as it doesn't get bloody. They will settle into a comfortable arrangement if you let them work it out.

Another thing you can do to help this along is to reinforce Sammi as the alpha. Once he is secure in your acceptance he will settle down. This means pet him first, feed him first, let him go outside first, etc... He needs to be first in everything! This goes against all your instincts probably to shelter and coddle the less dominant but if you do, you will be asking for more problems in the future.