I'm helping a buddy pick out his first AR 15. I own a couple colts, daniel defense and rock river arms so I'm not too familiar with smith Wesson, wihndam weaponry or dpms entry level AR 15. When I say entry level the prices I'm seeing at the stores are ($600-900). I noticed all the entry level ar15's don't have the castle nut staked. Do they use lock tight or similar or just tighten and leave it at that? If so any issues with castle nut coming loose? I could take the AR apart at cabela's do I'm also curious are the bolt carriers not staked earlier? Any input helps a great deal. Trying to figure out if I should tell my buddy to save a little longer and spend a little more.