I was all set to start building one a couple weeks ago when I ran into an issue I didn’t know existed: only a few receivers take Glock mags without an adapter. Not taking Glock mags is a deal-breaker. So I was back to square one in terms of finding proper parts and I told myself to just buy a complete one. I’ll check out ar15.com. Thanks.
There appears to be a lot of things you are not sure about. I suggest you buy a complete firearm.