Here are a couple of very good sites that might help:
www.m4carbine.net
M4 has a high density of very experienced pro's who know M4's and AR's.
Very work gun oriented and not much tolerance for phonies or bad info.
New people who want to learn are welcome.
www.theakforum.net
AK Forum is mainly a hobby site but is very high quality and quite well moderated.
Check out Practical Kalash.
Hope this helps.