Forums are an interesting exercise in frustration for new members. Threads and posts contain some of the most esoteric information at times, then later searches you might find exactly what you were looking for to the .001" of an inch.
In any and all cases, searching techniques are required, and making sure the terms used actually will bring up data. What's worse is that some search engines bring up listings based on the number of times the page was visited irregardless of whether it has any value. You can split screen your computer and literally type phrases in from a specific web page and Google will not list it. That same problem can exist using a forum search engine.
What doesn't happen is that there are hundreds of forumites eagerly waiting to serve a posters request for information. More likely, they scan for thread titles that interest them.
"Search and read" is the #1 advice given everywhere, a good long look through the sticky topics on the top of the page will often lead to hours of guided instructions and linked topics at other forums - ones that specialize in the particular topic. Ar15.com, m4carbine.net, lightfighter forums, among many others focus on the AR15/M16 in all it's variants, and have an extensive set of stickies to very specific topics.
"m16 lower blueprints" will get someone searching Google to a set of CAD drawings available for download - but even they aren't fully spec'd out. My copy doesn't list the thread specification for the barrel nut, which I had to find elsewhere. Brownell's listed it on the tap/die set description, 1 1/2' x 18 tpi.
The internet is a badly organized library, the information is out there, but it takes some work and creative thinking.
