If by MBUS you are referring to Magpul then using extra high rings should clear it.
I have an MBUS under a 3-9x40 scope mounted on a Leupold Rifleman see through rings on my M&P 15-22.
I also have a Troy BUIS under a Nikon M223 1-4x scope mounted on a M223 mount on my M&P 15 OR,
Picture below.