I have had this for a while now. It is one of my favorites. This is the breakdown of the current setup:
1- Custom 20" barrel. I got this from a friend who is one of those President's 100 who shoots all the time. It is stainless steel with a 1 in 7 twist. Where the gas block goes it is .75". Inside the hand gaurds it is almost as big around as the barrel nut. I cannot use the heat shields. He said he had it made but couldn't use it because at the time it was threaded for a flash hider; this was during the Brady Bill.
2- This is mated to a DPMS flat-top upper, with a Bushmaster bolt group.
3- The lower is Double Star with a Jewel trigger and otherwise stock A2 furniture.
4- For optics I am using a Simmons 3x9x40 and 45° offset A2 style sights.
5- The other hardware include a Rogers Tri-rail so I can mount a mil spec vertical grip with bipod, surefire 3P, and a Condor 3 point sling. I have a A2 style birdcage flash hider on the front end. The gas block is a quad rail style.
It is a fun rifle but kind of heavy.