Would loading a firework into a gun make it a Destructive Device?
<p>I've got a question inspired by a dream I had last night. If someone were to load a firework into a firearm, would that result in the firearm being classified as a Destructive Device? For instance, lets say you took a standard, breach-loading 12 gauge shotgun (barrel diameter just over 18 mm), and you inserted into it an 18mm fireworks rocket, followed by a blank shotgun shell to ignite the rocket's propellant.</p>

<p>Would that cause the shotgun and/or firework to become classified as a Destructive Device under the National Firearms Act? If it does, what actions would the owner of the weapon need to do to avoid breaking federal law?</p>

<p><a href="https://www.atf.gov/file/55446/download" rel="nofollow noreferrer">This ATF page</a> quotes from 26 USCA §5845(f)(2) as follows:</p>

<blockquote>
  <p>(f) Destructive device.--The term “destructive device” means * * * (2) any type of weapon by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, the barrel or barrels of
  which have a bore of more than one-half inch in diameter, except a shotgun or shotgun shell which the Secretary or his delegate finds is generally recognized as particularly suitable for sporting purposes; . . .”</p>
</blockquote>

<p>The hypothetical device you describe has a bore of > ½", and when fired would cause a projectile (the rocket) to exit the barrel. The rocket's firing is clearly caused by firing the blank shotgun shell, and would, I think, be seen as "expelling" the projectile. The objection that "the rocket fired and expelled itself" would not be persuasive.</p>

<p>Thus, I think the device you describe meets the statutory definition of "destructive device."</p>

<p>To avoid breaking this law, do not either a) insert a projectile (here, the rocket) in the shotgun bore, or b) set up any external mount or mechanism to ignite the rocket as a result of igniting a shotgun shell (blank or not blank) in the shotgun barrel. </p>

<p>Here's the problem.  You are using a gun-like contraption to launch something, <em>and that 'something' also has explosive properties</em>.  </p>

<p>This lands us right in front of the <a href="https://en.wikipedia.org/wiki/Saint_Petersburg_Declaration_of_1868" rel="nofollow noreferrer">St. Petersburg Declaration</a>, in which Russia invented  antipersonnel bullets with bursting charges, then called everyone together to ban them.  While the nascent US wasn't enough of a power to be invited to join that party, the doctrine nonetheless <a href="http://www.weaponslaw.org/weapons/exploding-bullets" rel="nofollow noreferrer">is part of human rights law</a>. </p>

<p>Of course, at the Geneva Convention level, nobody bats an eye at <a href="https://en.wikipedia.org/wiki/Rifle_grenade" rel="nofollow noreferrer">rifle grenades</a>, which use the energy of a shell or blank discharge to launch a grenade, the very definition of a thing with explosive properties.  But those, while perhaps not entirely illegal, <a href="https://www.quora.com/Can-you-legally-own-a-rocket-launcher-in-the-USA-without-having-a-demolitionist-position-in-the-military" rel="nofollow noreferrer">are obstructed to the point of futility</a>.</p>

<p>As DavidSupportsMonica discusses, you also run into a technicality: firing <em>anything</em> out of a barrel larger than 1/2".  While there is an exception for things that look, walk and quack like plain old shotgun buckshot, that plainly doesn't apply to fireworks. </p>

united-states firearms