I built an ultralight about 5 years ago. It was a lot of fun trying to get the weight off everywhere I could. It really worked well. I think my gun come in at just about 5 pounds. No one part takes off a ton of weight, but going with the pieces that are a couple ounces lighter everywhere you can adds up. Use a Colt shaved bolt carrier, use a lightweight barrel (without bayo lug if possible), use the old style 4 position stock, use the lighter handguards, use a flat top with BUIS, or, an old A1 upper without forward assist or brass deflector. Individually, you may not notice the difference in one of these lighter parts over the standard. But add it all up and you will notice the difference. Have fun and good luck! Post pics when youre done!