Are Simunitions conversion kits firearms?

There are two kinds of firearms under U.S. (federal) law, title
1 firearms and title 2. Title 1 firearms are long guns (rifles and
shotguns), handguns, silencer, and firearm frames or receivers.
Most NFA weapons are also title 1 firearms. Title 2 weapons are
NFA weapons. Title 2 of the 1968 Gun Control Act is the National
Firearms Act (codified at 26 U.S.C. sec. 5801 et seq.), hence NFA.
Title 1 is generally called the Gun Control Act, (18 U.S.C. sec.
921 et seq.). NFA weapons are also sometimes called class 3
weapons, because a class 3 SOT (see below) is needed to deal in NFA
weapons.

NFA weapons are: machine guns, sound suppressors (a.k.a.
silencers), short barreled shotguns, short barreled rifles,
destructive devices and "any other weapons". Exactly what these
weapons are is defined in the law, as well as in court cases
interpreting the law.

Any other weapons (AOW's) are a number of things; smooth bore
pistols, any pistol with more than one grip, (but see below) gadget
type guns (cane gun, pen gun) and shoulder fired weapons with both
rifled and smooth bore barrels between 12" and 18", that must be
manually reloaded (see discussion below).

These definitions are simplified, to see if a specific gun is a
title 1 or 2 firearm one needs to refer to the specific definition
under the statute(s), and possibly consult with the Technology
Branch of ATF. There is also case law on the issue of whether a
specific item falls into one of these categories. In addition, as
a general rule, a parts kit, i.e. all of the parts to assemble an
NFA firearm, whether a parts kit is specifically included in the
statute or not, is usually considered to be the same as the
assembled firearm.

12001. (a) (1) As used in this title, the terms "pistol,"
"revolver," and "firearm capable of being concealed upon the person"
shall apply to and include any device designed to be used as a
weapon, from which is expelled a projectile by the force of any
explosion, or other form of combustion, and that has a barrel less
than 16 inches in length. These terms also include any device that
has a barrel 16 inches or more in length which is designed to be
interchanged with a barrel less than 16 inches in length.

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