The question of whether BBs are magnetic is common, stemming from the small, spherical projectiles’ widespread use in air guns and the various materials from which they are constructed. BBs are small, round projectiles, typically around 4.5 millimeters (0.177 caliber) or 6 millimeters in diameter, that are launched by spring, pneumatic, or gas-powered devices. The confusion regarding their magnetic properties is due to the difference in the materials used for airsoft BBs versus traditional air gun BBs. While some BBs are plastic or non-ferrous metals, the most common type used in traditional BB guns exhibits a strong magnetic attraction.
The Definitive Answer Material Dictates Magnetism
The magnetic response of a BB depends entirely on its composition. Standard air gun BBs are predominantly made of steel, which is magnetic, and are often coated with a thin layer of copper or zinc for corrosion resistance. This coating does not change the fact that the underlying steel core will be strongly attracted to a magnet. In contrast, the BBs used in airsoft guns are generally non-magnetic because they are made of plastic polymers, such as ABS or polylactic acid (PLA) for biodegradable versions. Other metal BBs, such as those made of lead, zinc, or certain alloys, are also non-magnetic, as they lack the necessary internal structure to be pulled toward a magnet.
Understanding Ferromagnetism in Steel
The reason steel BBs are strongly magnetic lies in a specific type of magnetism called ferromagnetism. This property is determined by the presence of iron, nickel, or cobalt, and steel is primarily an alloy of iron and carbon. Iron atoms naturally possess unpaired electrons that act like tiny, atomic-scale magnets. Within a piece of ferromagnetic material like steel, these atomic magnets align themselves into small regions called magnetic domains. In the absence of an external magnetic field, the domains point in random directions, canceling each other out. When a magnet is brought near, the external magnetic field causes the domains to rotate and align parallel to the field. This alignment results in a powerful net magnetic force, causing the BB to be attracted to the magnet.
Practical Applications of BB Magnetism
The magnetic nature of steel BBs has several practical consequences concerning cleanup and detection. The most immediate application is the ease of collecting stray BBs after target practice. A strong magnet can be quickly passed over a collection surface to gather the steel BBs, making cleanup faster than manual collection. Magnetism also plays a role in safety and detection, as steel BBs will be detected by common metal detectors in security or industrial settings. From a medical perspective, if a steel BB is accidentally ingested or embedded, its ferromagnetic property means it will be clearly visible in medical imaging, such as an X-ray or MRI screening. The presence of a ferromagnetic object must be considered a safety concern in the powerful magnetic field of an MRI machine, as the magnet could cause the BB to move.