In the theme of making your AR-15 lighter Fostech Outdoors may have taken the market lead with their 3.5 pound AR-15.
Fostech has used all of the current tricks and technologies to bring the weight of their AR-15 down. A mixture of artful skeletonizing of unstressed parts, using carbon fibre tube and folded flats for the buttstock, and using the woven Brigand Arms handguard has saved an incredible amount of weight.
With a pencil thin free floated barrel the rifle will achieve 2MOA with standard ball ammunition. This overall package is light enough to be shot one handed, or held up on target for greater amounts of time than competing rifles of greater weight.
So is this too much weight saving, and is this a niche design? It could be a rifle for lighter framed shooters, and will certainly have an appeal to backpackers and cross country hikers where every ounce is measured. It certainly is an interesting design that comes in at nearly half of the weight of any competitors rifle.