I spend time every Saturday morning on the internet, just some quiet time before getting down to business for the day. I am amazed at the number of people machining AR-15 and AR-10 lowers.
I know very little about guns and haven't owned one myself since giving up Duck hunting in the late 80's. I do like them and will someday own a nice AR.
So whats the deal ? why are so many shops large and small making these parts ? Who buys them ? What are the advantages over the factory produced lower ? What are the laws around the manufacture and sale of these parts ? The market must be flooded and the price of the part must be beat to hell by now ?
I don't plan on doing this I've had a few guitars on the drawing board for years now and I'm so busy making parts for my customers they will never get made, I'm just curious.
Fill me in Boys !
Make Chips Boys !
The reasons why the AR platform is popular are pretty simple:
1. Since the 1991 Gulf War, we've had hundreds of thousands of men and women who have cycled through our military forces. The M-16 or M-4 is "their gun." Just as the 1903, 1917, M1 Garand and M1 Carbine used to be very popular in the civilian world with prior generations, (I can remember when a Carol Burnett Show episode had a M1 Garand a prop), the civilian version of the rifle that so many people trained with is "their rifle." They view the prior rifles of the US military as antiques and curious - nice, but not "their rifle."
2. The AR is easy to work on. Most things you could or would do to an AR need no mill, no lathe, no real gunsmithing knowledge. You can buy into almost every tool you'd conceivably use on an AR for less than $500 - all the wrenches, fixtures, gages, etc are easily available.
3. You can detail strip an AR in less than 15 minutes once you get good at it. When I'm on top of my game, I can detail strip an AR down to the pins and detents, and re-assemble it to spec in less than 30 minutes. It is a very straightforward gun to clean and re-assemble.
4. You can own one lower (the part with the serial number) and as many "uppers" as you'd like, changing uppers on/off the lower (which contains the trigger group, magazine catch, safety, etc) takes less than a minute. You can have a variety of barrel lengths on the uppers, or even different chamberings. One serial number, 'n' actual different guns.
5. There's a million and one accessories for them. AR's are a Lego set for adult shooters. If you're wondering how many accessories or parts for an AR are available, just get a Brownells catalog. The Brownells catalog is organized from the most popular guns in the front of the catalog to the least common/popular guns in the back. The greatest number of pages devoted to any gun in the Brownells catalog is for the AR-15, and it occupies dozens of pages in the front of the catalog. Brownells doesn't carry even half of the accessories available for AR's in the market - just the stuff their customers have requested.
6. Riffing off points (2) and (4), you can install a new barrel on an AR without needing a lathe - and most guys changing over barrels don't even use headspace gages. They just get a new barrel with the extension screwed/pinned on there, a new bolt (or a new bolt & carrier) and slap it together. Done.
AR's are light, accurate, easy to work on, have low (or almost no) recoil, have excellent trigger groups now available for them, etc.
Now the reason why the 80% lowers are popular? Some people want the DIY experience. Some people want less paper trail. Some people want special features.