Almost every major metropolitan area in the country now has some sort of "maker" workshop club or business. Joining is $50-$100 a month.
http://themanufactory.us/floor-plan/
If you have one of those in your area, and I'd guess the majority of the US population has one within an hour, an 80% and much more can be completed pretty easily.
"Major Metropolitan Area" is viewed very differently, depending upon what part of the country you are in.
For people in certain parts of the midwest, or along a coast, there are generally more options. But much of the country still doesn't have reasonable access to any kind of 'maker workshop'. In some parts of the country, a "Major Metropolitan Area" might be a city of 15,000 people, that's still 2-3 hours away.
Even when I lived in a metropolitan area with a population of 1.3 million people, the closest workshop/hackerspace was 6 hours away (Las Vegas, NV -- and it's
still the closest to SLC). ...And there was a 14 month wait for machine time on even the manual mills and lathes.
Where I am now, the closest facility is still Las Vegas. Except, now, it's a 9 hour drive. ...Or 9.5 hours to Denver, CO. ...Or 10 hours to Portland, OR.
And most of them didn't allow work on, or manufacture of firearms or firearm parts,
before 2015-1. Now that 2015-1 is out there, I don't know of a single workshop/hackerspace that'll even let you in the door if there's any suspicion of firearms or parts being made or modified.