Thanks for the anwsers.
Getting more to the point, are these the reasons why an KJW M4A1 is not as accurate as an WA M4A1?
Also, if the WA system is more accurate? Is it possible to buy an AGM M4A1 (WA clone) and replace the hop up, bucking and barrel to make a good accurate M4A1?
About BBs. I plan to use BB Bastard .20 for games then Silica BB Bastrads for basement plinking.