Soft point

A soft-point bullet (SP), also known as a soft-nosed bullet, is a jacketed expanding bullet with a soft metal core enclosed by a stronger metal jacket left open at the forward tip. A soft-point bullet is intended to expand upon striking flesh to cause a wound diameter greater than the bullet diameter. Jacketed soft point is usually abbreviated JSP in the ammunition and reloading industry.

Lead-alloy bullets used with gunpowder firearms were unsatisfactory at the bullet velocities available from rifles loaded with nitrocellulose propellants like cordite. By the late 19th century, lead-alloy bullets were being enclosed within a jacket of stronger mild steel or copper alloyed with nickel or zinc to reliably impart stabilizing rotation in rifled barrels. The lead-alloy core was swaged into a cup of the stronger metal covering the front and sides of the core, but leaving some of the core exposed on the base of the bullet. The bullet jacket may be described as a metal envelope, steel envelope, or hard envelope; and the jacketed bullet may be described as metal-covered, metal-patched, or metal-cased.

These jacketed bullets fired by modern rifle cartridges were typically of smaller diameter than lead-alloy bullets of earlier gunpowder cartridges, and the stronger jacket made them less likely to be deformed during handling or loading. The tendency of jacketed bullets to pass through an animal with minimum deformation or expansion was perceived as a more humane way to incapacitate military soldiers, but was considered less effective for killing hunted animals. Reversing the direction of jacket placement leaves the exposed lead-alloy core on the forward tip of the bullet creating a soft-point bullet.

Soft-point bullets expose the soft lead-alloy core on the forward part of the bullet most likely to be deformed when striking a target. The sides of the bullet remain covered by the jacket to reliably impart stabilizing rotation from rifling. Expansion of a soft-point bullet depends upon the hardness of the lead-alloy core, the strength of the surrounding metal jacket, and the energy available from the decrease in bullet velocity as the bullet encounters target resistance. A core of pure lead is softer than a core of lead alloyed with metals like antimony and tin. Some jacket alloys have greater tensile strength than others; and, for any given alloy and annealing process, a thicker jacket will be stronger than a thinner jacket. Energy available to expand the bullet is proportional to the square of the velocity at which the bullet strikes the target. If the bullet passes through the target, the energy represented by the square of the velocity of the departing bullet has no effect on the target. Soft point bullets may not expand if they strike a target at low velocity, or if the target does not slow the bullet enough to deform the exposed point or rupture the surrounding jacket.

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