this is sorta the wrong place to post this question.. for a couple of reasons.
One this is the area for posting problems you are having with the Forum... not general discusion or asking gun problems ( i dont mind, others might , but it is not likely to get seen by the "right" people here )
Second this whole forum does not deal so much with the AR pistol or otherwise as much as it does with certain chamberings ( .300 whisper in particular)
My suggestion would be to go to the AR15.com board and ask there....
here is a link to a thread over there that pretty much beats this subject to death, caution ! there are 14 pages of posts! I would suggest you sit back and read them all! lots of good info.
http://www.ar15.com/forums/topic.htm...8&t=200876
Good luck, I am starting today to build one of them little critters, check back and we can compare notes.
Dan