How is the Serbu GB 22 not NFA?

[grampajack]

I thought the ATF had banned open bolt firearms? Does the absence of a magazine make that non applicable?

For those who don't know, the GB22 is a zip gun that is single shot. It's fired from an open bolt with a fixed firing pin.

 

[pintler]

Does the absence of a magazine...

There's your answer. The legal definition of 'machine gun' is in 26 USC 5845: "The term “machinegun” means any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger."

That definition is a functional one. It doesn't say anything about open bolt, selector holes, rate of fire, etc, etc. It's all about whether pressing the trigger once fires two or more shots. For example, I think that if you rigged something with a double barreled shotgun so that you pull the trigger and one barrel fires now and starts an hourglass that somehow fires the second barrel tomorrow, that would be a machine gun per the law - because it fired twice with one trigger pull.

So the GB22 question is whether it can 'shoot ... more than one shot, without manual reloading'. The manual loading requirement prevents it from being a 'machine gun'.

Along with the 'or can be readily restored to shoot' requirement, or course. That's why AR lowers with the selector hole are forbidden; with the hole drilled all you'd have to do is install the right parts to make it full auto. You'd have to do more than drill a hole to fit a magazine to the GB22.

 

[MachIVshooter]

I thought the ATF had banned open bolt firearms? Does the absence of a magazine make that non applicable?

Open bolt guns aren't explicitly banned; it's the nature of the design being "readily convertible" which makes them (generally) contraband. If you designed one that couldn't be turned into a machine gun or stutter gun by removing parts, it would actually be legal. Thing is, it would end up more complicated than a closed bolt design. I pondered it for incorporation into an ultralight design, since the advanced ignition of open bolt allows for a lighter bolt (momentum + inertia rather than just inertia), but came to the conclusion that the complexity of making a non-convertible open bolt would be fickle and not end up saving much weight at all.

For those who don't know, the GB22 is a zip gun that is single shot. It's fired from an open bolt with a fixed firing pin.

I wouldn't call it a zip gun. A simple design, but not something that can be cobbled together with some hardware store pieces. There's some precision metalwork involved. Mark sent me a set of plans and suggested I make a "nice" version of it, which I did with stainless steel and wood, chambered it in .380 with a threaded barrel:

 

[entropy]

Looks kinda like a Beretta and a Glock fooled around.....nice work!

 

[tark]

I wouldn't call it a zip gun. A simple design, but not something that can be cobbled together with some hardware store pieces. There's some precision metalwork involved. Mark sent me a set of plans and suggested I make a "nice" version of it, which I did with stainless steel and wood, chambered it in .380 with a threaded barrel:

Very nice! that is some impressive work there.