Yes! If you Google "Brownells Two Piece AR Gas Block". You will see they have a couple of styles. They attach with four hex screws. The one I have has the Picatinny Rail on the top and the bottom. But they also have on with the Picatinny Rail on the top and Bayonet Lug on the bottom.
The Constitution is not an instrument for the Government to restrain the people. It is an instrument for the people to restrain the Government!
America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves.