Here is one of our favorite custom builds. We decided to try and rebuild the old school C7 M-16A1. These are using a .750 gov profile barrel with a 1/7 twist. The barrel is made of 41V50 steel and the chamber/bore is chrome lined. We have also used a A1 Bird cage flash hider on it. C7 Upper receiver is black finished. Handguards are skinny colt style.
Take a look at this great article about our upper http://www.gunsandgunsmiths.com/retro-ar-project/
This item carries a lead time. Typically it is 2-3 weeks. Due to product availability lead times may vary.