Dude, the original Armalite/Colt clip on style lets you swivel side to side. And it clips to the barrel, so your bipod mount is already there, NO extra weight! Don't think there is a lighter bipod either? AND, if you get one of the ones made out of plastic (does anyone make them like they did back in the 70's and 80's?), it doesn't rust and it doesn't marr your barrel. Ever see a 180 that has two bright silver rings around the barrel right in front of the sight tower? That is because Armalite made a "keeper" ring on the barrel to keep the bipod in one place on the barrel, leading to a wear ring.
Almost forgot, the bipod clips to the AR-15 barrel under the sight tower. You just don't see anybody hardly using that old style any more, but it was simple and effective.