Editing Soft-point bullet (section)

==Expansion==
[[File:FMJorSPbullet.png|thumb|This image illustrates the jacket placement difference between [[full metal jacket bullet]]s on the left and soft point bullets on the right.  Both bullet types are {{convert|220|gr|g|sing=on}} .30-caliber. The silver-colored [[cupronickel]] jacketed bullets on the left have an enclosed rounded point with a jacket opening on the flat base, while the copper-colored [[gilding metal]] jacketed bullets on the right have an enclosed flat base with a jacket opening on the rounded point.]]
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 (metallurgy)|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.<ref name=pbs/>

[[Varmint rifle]] bullets with thin jackets are intended to expand rapidly and disintegrate upon encountering minimum resistance. Bullets intended for [[big-game hunting]] are designed to increase their forward diameter while remaining intact to penetrate deeply enough to damage internal organs likely to cause rapid death. Big-game bullets sometimes have a specialized jacket including a center baffle between a forward core intended to expand and another core intended to remain intact. Alternative designs include a jacket with an internally thicker belt around the central part of the bullet intended to resist expansion while the thinner forward part of the bullet jacket ruptures. Some bullets have a core formed from a soft alloy in the forward part of the bullet bonded to a harder alloy core in the rear of the bullet. Others have a jacket which is thicker near the base of the bullet and tapers to a thin fringe adjacent to the soft point.<ref name=pbs/>