Edited for a complete list:
After modification: 5.73lbs
10.5" Midwest SSK-Keymod Series Handgaurd with barrel nut 7.7 oz
Aero Percision Lightweight 30mm mount 3.27 oz
Aero Precision slick side upper receiver 6.6 oz
Removed 3 ounches of the weights in the buffer
Replaced the pistol grip with the Magpul K 2 oz
Minimalist Stock 5.8 oz.
Note: This stock is a much tighter fit than the Magpul CTR
Replaced the FA BCG with a SA BCG with steel 6.8 bolt 11 oz
Syrac Gen II solid adjustable gas block 1.5 oz
Been contemplating on replacing the buffer tube and stock with the Smoke Composite stock which would reduce the weight by another 5-8 ounches.
Reused existing parts:
Leupold VXR 1.25-4x20 with Pig Plex 11.5 oz
6.8 SPC II Wilson Lightweight Hunter 16" barrel 24.8 oz
Mid length SS gas tube .7 oz
Wilson Combat Accu-Tac Flash Hider 2.2 oz
Mil spec 6 postion buffer tube with castle nut and back plate 5 oz
Standard charge handle 1.2 oz
Carbine (10.5") length buffer spring 1.9 oz
Buffer body (after removing 3oz of weights) 1 oz
PlumCrazy Lower with steel takedown pins, polymer safety, polymer mag release,polymer trigger group, and steel bolt release 9.2 oz
She weighs under 5lbs (4.86lbs) without the scope, mount and loaded mag.
Note: These are not the lightest components and could have gotten her under 4lbs, but I went with what I thought to be reliable parts (along with balance or feel) without breaking the bank. Before somebody makes a remark about the plumbcrazy lower, I have had this lower on various 22lr, .223/5.56, and 6.8 uppers with over 5,000 rounds fired so no need for snide comments.