BCM introduced some new lightweight fluted barrels along with their light weight keymod handguards.

Their enhanced lightweight barrels are .4 oz lighter than their normal lightweight barrels.

The fluted elw barrels are 0.75 oz lighter than the non-fluted elw barrels. Making them over one ounce lighter than the normal lightweight barrels.

 

http://www.bravocompanyusa.com/BCM-14-5-Mid-Length-ELW-KMR13-p/bcm-urg-mid-14elwf-kmr13.htm

 

Just for reference, the KMR is very light.

 

BCM KMR13: 5.5 oz (Rail) + 2.2 oz (Barrel Nut) = 7.7 oz

 

Noveske NSR 13.5": 7.9 oz (Rail) + 3.1 oz (Barrel Nut) = 11.0 oz

I built a Magpul 14.5" upper today and slapped it on a Spikes lower. the total weight without a mag is 6lb 3.2oz. I'll weigh it tomorrow with a Polymer lower for comparison.

 

AP custom carbon fiber free float tubes. Lightest forearm for the money $125 for the midlength at cactus tactical (dunno if it is the best price, they don't sell direct anymore it seems, and it was on their vendors list and I ahve done business with them before without issue). 

 

But I have an aero precision upper with ar15performance lightweight 16"  barrel (25oz), a yhm gas block flip up sight combo, mid length ap custom handguard, ARFX skelton stock (a1 length), rifle buffer, MIAD grip, drop in trigger pack, and a semi auto BCG setup, and magpul MBUS rear sight. COmes in at about 5lobs 9oz IIRC. Under 6lbs.