Ive been interested in building the "expedient homemade firearms 9mm" if you guys arent familiar it has a 14.5 inch barrel and is constructed of standard pipe and tube from any steel supplier. Would something like that be against the laws to make?
Uhh... yeah don’t build that. Those are plans for an open bolt submachine gun. As discussed above, new machine guns are a no-go. Same with any open bolt firearm even if it functions as a semi-auto only (though there are some small exceptions that aren’t worth getting into here).
Changing an open bolt submachine gun design into a legal closed bolt semi-auto design is a significant undertaking involving a lot of receiver and parts redesign. You’re literally changing everything about how the gun operates. Even manufacturers have trouble with the transition sometimes. Not to be mean, but if you don’t know how triggers work, you shouldn’t attempt a conversion like this as a first build.
There are lots of other issues with that design, but the glaring one is that it was designed to be made in an environment where no gun parts are readily available. That is NOT the case with us here in the US.
For example, if you use a barrel made out of some random pipe, you don’t have good (if any) rifling and likely won’t have a correct chamber reamed. That means you either run the risk of cartridges going too far down the barrel or firing before they are fully seated, resulting in an out of battery detonation. It is much easier and safer to just buy a real barrel, especially when they are unregulated.
Same thing with magazines. Mags are often the main source of weapons malfunctions, and can be tricky to get right. Just buy some real mags as opposed to trying to build your own.
If the gun you build is a rifle, it must have at minimum a 16” barrel (as measured by a rod put down the barrel, resting on the breach face). Best practice is to go just a bit longer than 16” so there’s no question. Getting it wrong is a felony.
I understand the excitement behind wanting to get into your first build, but I HIGHLY recommend you start off with something that is more formulaic and easier. For one, you’re likely to be able to find a lot of people who can help with questions (as opposed to asking “how do I fix this problem with my illegal SMG”).
Remember for legal purposes, the Receiver is the actual firearm - just about everything else can be ordered and shipped to your house. The easiest home build guns I can recommend are something like a Polymer80 (for a pistol) or an 80% AR (if you want a rifle). Those will let you build the lower, and then just order the rest of the parts.
If you want something a little more involved, look at building an AK. But be warned, you’ll need a good bit of machinery and tooling. Definitely doable, but you’re not going to be putting it together at your kitchen table.