Thy Lpy 4.5x14 is my fav Leupold scope in both the VXIII and M4. They are light, compact, good glass and tough. For 400 m this in more than enough scope with the option to go much longer. Are you talking 1 inch or 30mm, if 1 inch and weight is not a big concern the Zeiss Conquest is a great option as well, a bit better glass than the Lpy but you give up weight.