Re: ar-15 ??
Assembling your own lower is very simple. I did it myself without help (other than pictures/instructions) in about an hour and a half. I think I had the TV on, too. Now that I've done one, I really believe that it could be done in about 30 minutes without too much trouble.
Assembling your own upper is more difficult because you have to worry about headspacing, but it can be done. You can also buy a "complete" upper which will have all you need or an "upper assembly" to which you will need to add a bolt carrier group and a charging handle. I bought a complete upper, and assembling it to the lower took about 15 seconds.
Many gunsmiths build great ARs, too, but don't think that you have to be a gunsmith to work on ARs. That really is an "armorer" weapon rather than a "gunsmith" weapon.
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