If one were to search for how to build up an AR-15, a veritable smorgasbord of options would present themselves after a search. Almost all the noted YouTube personalities have a how-to video. From there, there is literally thousands of others ready to assist the burgeoning smithie on their quest for Armalite Rifle nirvana.
However, outside the common Modern Sporting Rifle platform, there are few similar videos on the detailed assembly operations of other platforms, especially those that require custom fitting. Most AR’s just “bolt together”, which is still out of the reach of some assemblers.
To assist fellow enthusiasts, TonyBen3 on YouTube has put up exhaustively detailed videos on the M14 / M1A. He’s gone into incredible detail on some of the more advanced (an operation typically reserved for “gunsmiths”). But, before one can progress to locking in accuracy of their build, one must build a rifle, which is where TonyBen shines.
Note, these types of videos will not show one actually how to do various common milling, filing, or sanding operations, but they are excellent at showing one what they should be watching out for and what is considered ideal for the weapon system.
My hat’s off to him on showing the proper method to lap in a bolt and then set headspace on the weapon.