My first build was an ultralight.  I used a Bushy superlight barrel, Clark (same as DPMS) carbon fiber free float tube), Les Baer flattop upper w/o forward assist and a Cav. Arms Mk II lower.

Now I'm thinking about making that build (build 1.1) even lighter or building a new, lighter, ultralight from scratch (build 2.0).  Why?  Because I can.

Here are some ideas I'm kicking around.  Let me know what you think>

1.  Drill holes in the carbon fiber free float tube to further reduce weight and for a "perforated barrel jacket" look.

2.  Bushy carbon-fiber upper (I'm aware of the problems some people have had with them)

3.  JP Rifles low-mass stainless bolt carrier and speed trigger

4.  ABS 16" carbon wraped barrel w/no muzzle device

5.  (Maybe) Bushy carbon fiber lower and ACE AR15 Ultra Lite Stock to permit using JP Rifles 2.5 oz. low mass buffer and 3.5 oz 7075 carrier.  I still have to do the math to see if this would result in a lower overall weight than a Cav. Arms Mk II lower and JP's low-mass stainless carrier.

Either way I'll use a 2.3 oz. OKO sight.

The general idea is to minimize weight maximize carbon fiber and end up with an accurate carbine that is reliable enough for recreational (non-life critical) use.