How to (Legally) Make Your Own Off-the-Books Handgun: BUILD A GLOCK 17 USING PARTS FROM THE INTERNET.

• Author: McDaniel, Mark

LET'S START WITH a disclaimer: If you have little to no experience with guns, it's probably not wise to try assembling your own. It can be dangerous to make a mistake--even deadly. There's no shame in buying a firearm from a reputable manufacturer and then taking a class to learn how to handle it safely, defensively, and intelligently.

But do-it-yourself has its appeal as well. For those who already have basic firearm know-how and competence with common tools, it's easy to make a gun that's just as safe as one bought from a store.

It's also perfectly legal in most American jurisdictions. That simple fact tends to be ignored by pundits and politicians in the debate over gun control. But if even moderately skilled people can create their own weapons at home--and increasingly they can--then passing laws to regulate commercial manufacture and sale starts to look awfully futile. While firearm restrictionists will likely soon be clamoring for laws to rein in private production, there's only so much they can do: Communicating instructions for how to build a gun is constitutionally protected speech, after all.

In celebration of the First Amendment, let's walk through how to make a weapon based on one of the most popular semiautomatic handguns in the world: the Clock 17, a full-size double-stack 9 mm pistol with a track record of reliability and simplicity. Recently, third-party companies began marketing "frame kits" that allow private individuals to make guns that look and operate like Glocks and are compatible with Clock parts. There's a caveat, however: Their product includes excess plastic that, unless removed, prevents you from turning it into a functional weapon. By itself, the object they sell doesn't count as a firearm in the eyes of the law. Instead, it is colloquially known as an "80 percent frame" or an "80 percent receiver."

This will be the platform for our homemade gun.

HOW IS THIS LEGAL?

GUNS ARE REGULATED in various ways. The same is not true for an object that happens to be transformable into a gun by a skilled home hobbyist.

Despite the name, though, the difference between a gun and such an unregulated object isn't as clear-cut as some sort of "80 percent rule," says attorney Mark Barnes, a D.C. lawyer who specializes in issues involving the import, export, and manufacture of firearms. "The fact of the matter is that firearms design differs from gun to gun. As a consequence, the final judge on whether or not a physical object constitutes the frame or receiver of a firearm is the Firearms and Ammunition Technology Division of the Bureau of Alcohol, Tobacco, Firearms, and Explosives" (ATF).

If you send ATF an object, the bureau's experts will explain why it is or isn't a firearm according to two main laws. The Gun Control Act of 1968 defines a firearm as "any weapon...which will or is designed to or may readily be converted to expel a projectile by the action of an explosive," or "the frame or receiver of...