12-01-2014, 01:29 AM
For absolute mechanical accuracy it starts with a square upper receiver face to seat the barrel extension against, bedding the barrel extension in the receiver, having a free floated barrel, making sure the gas tube is centered and does not rub against one side or the other of the gas key when the bolt carrier group moves forward, and a good trigger. The quality barrel is important also. If you use the google search in the pinned subjects at the top of this discussion board you will find many threads with good information. Billet upper receivers are stiffer and suppose to help with accuracy also. These things just apply to the mechanical accuracy the rifle is capable of. Shooter ability is a whole other topic.