Please help me build my dream AR. I am looking to buy or build a lightweight A.R. 15. I am wanting it to come in at around 5 pounds, have a 18 inch barrel, with a carbine length gas system,1/12 twist barrel in 5.56/223. I want the 1/12 twist barrel because I plan on shooting the NOE 60 grain bullet and it will have an adjustable gas block so what do you think any advice?