Welcome.
If your going to build, and plan on using all DPMS parts, why not just buy a complete rifle? You'll get a warrantee with it.
The receivers are generally what dictate what the build is called. It's really not a big deal, people generally pick out parts they want and assemble. It's normal when building, and actually the reason people primarily do it.
It's also a pattern. There is no mil spec on these large frame AR'S, and you will need to pick out a pattern and coordinating parts. Armalite is the ar10 pattern, DPMS/sr-25 is a the lr308 pattern (heh, mostly), then there is rock river which uses there own (and FAL mags)