What is considered a "short-barreled rifle" in legal terms?

A "short-barreled rifle" is legally defined as a rifle with a barrel length of less than 16 inches. This definition is established under the National Firearms Act (NFA) and other relevant firearm regulations. The requirement specifically identifies the necessity for barrel length as a distinguishing characteristic of firearms that fall under more stringent regulation due to their potential concealability and lethality.

In this context, the other options do not align with the legal definition. While firearms designed to be easily concealed may overlap with the characteristics of a short-barreled rifle, the law does not equate concealability with the specific criterion of barrel length. The general reference to any rifle used for hunting does not specify barrel length and could include any standard rifle. Additionally, a standard rifle modified to have a shorter barrel could be considered a short-barreled rifle only if the modification results in the barrel measuring less than the legal threshold. However, the correct definition does not depend on the rifle's original design, but rather on the final barrel length. Therefore, the clear and specific criterion of barrel length is what makes the first answer the legally accurate one.