Ron, unless they moved destructive devices to an issue regarding conservation, it's not Title 16
, it's in Title 18 Part 1
Here's the definition according to the law:
TITLE 18 > PART I > CHAPTER 44 > § 921
The term “destructive device” means—
any explosive, incendiary, or poison gas—
rocket having a propellant charge of more than four ounces,
missile having an explosive or incendiary charge of more than one-quarter ounce,
device similar to any of the devices described in the preceding clauses;
any type of weapon (other than a shotgun or a shotgun shell which the Attorney General finds is generally recognized as particularly suitable for sporting purposes) 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, and which has any barrel with a bore of more than one-half inch in diameter; and
any combination of parts either designed or intended for use in converting any device into any destructive device described in subparagraph (A) or (B) and from which a destructive device may be readily assembled.
The term “destructive device” shall not include any device which is neither designed nor redesigned for use as a weapon; any device, although originally designed for use as a weapon, which is redesigned for use as a signaling, pyrotechnic, line throwing, safety, or similar device; surplus ordnance sold, loaned, or given by the Secretary of the Army pursuant to the provisions of section 4684 (2), 4685, or 4686 of title 10; or any other device which the Attorney General finds is not likely to be used as a weapon, is an antique, or is a rifle which the owner intends to use solely for sporting, recreational or cultural purposes.