When does a block of metal become a gun? There is usually one specific piece that counts as the legal firearm, while all the other parts, such as springs and barrels, are simply metal shapes that anyone can buy anywhere. People sell chunks of metal that are 80% of the way to being the specific part that is the gun, but not yet legally firearms. Using some tools at home, you put the finishing touches on it, then add the many other unregistered parts that go with it. This way you never buy a tracked part. They've been cracked down recently, but are still available. This is the whole ghost gun thing that politicians freak out about.

When does a block of metal become a gun? There is usually one specific piece that counts as the legal firearm, while all the other parts, such as springs and barrels, are simply metal shapes that anyone can buy anywhere. People sell chunks of metal that are 80% of the way to being the specific part that is the gun, but not yet legally firearms. Using some tools at home, you put the finishing touches on it, then add the many other registered parts that go on it. This way you never buy a tracked part. They've been cracked down recently, but are still available. This is the whole ghost gun thing that politicians freak out about.