Hello, is it possible to make a RAS sytem that is mounted onto a M4 free floating? Can you add the free floating tube under it? Can somebody tell me the difference in weight between a M4 RAS and a M4 RAS FF? Thanks

Even if you could make the RAS free float by putting the tube under it would would destroy the ventialtion and youd end up with a barrel that heats up too fast and weighed way too much.  The FF RAS is heavier than the RAS though due to its large barrel nut.  If weight is REALLY an issue there is the Daniel Defense forearm that has an aluminum barrel nut.

There is a thread with the weights on all the various forearm systems.  I am sure someone will provide you with a link to that chart.  I am just too lazy to find it for you.