From what I understand about the m&p is that the upper and lower are also prepriotory. So no upper on the market will work with the m&p lower.
I have talked with the people at black hole weaponry and they will build a barrel and use the factory barrel extension so that it will work with the...
Man this is some awesome news. I will be calling BHW in the AM and discuss with them about putting a new barrel and BCG. Get that proprietary **** out of that gun