Global Tactical has been selling an excellent bolt carrier group (BCG) called the Super Duty Bolt for years now. I have been very pleased with the one that I have in my range/training rifle. It is in excellent bolt that meets or exceeds mil-spec. The Super Duty Bolts were basically hand built by Global Tactical. Now Global Tactical has found a manufacturer who will make BCGs to their specs. This will help keep costs down which is good news for consumers.
The new BCG is called the Thunder Bolt. Check it out at Global Tactical.