Editing Bullet (section)

==Design==
{{unreferenced section|date=May 2023}}
[[Image:Bullet coming from S&W.jpg|thumb|A bullet in mid flight]]Bullet designs have to solve two primary problems. In the barrel, they must first form a seal with the gun's bore. If a strong seal is not achieved, gas from the propellant charge leaks past the bullet, thus reducing efficiency and possibly accuracy. The bullet must also engage the rifling without damaging or excessively fouling the gun's bore and without distorting the bullet, which will also reduce accuracy. Bullets must have a surface that forms this seal without excessive friction. These interactions between bullet and bore are termed [[internal ballistics]]. Bullets must be produced to a high standard, as surface imperfections can affect firing accuracy.

The physics affecting the bullet once it leaves the barrel is termed [[external ballistics]]. The primary factors affecting the aerodynamics of a bullet in flight are the bullet's shape and the rotation imparted by the rifling of the gun barrel. <ref>{{Cite web|url=http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA505719|title=EFFECT OF RIFLING GROOVES ON THE PERFORMANCE OF SMALL-CALIBER AMMUNITION Sidra I. Silton* and Paul Weinacht US Army Research Laboratory Aberdeen Proving Ground, MD 21005-5066|archive-url=https://web.archive.org/web/20121006194613/http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA505719 |accessdate=15 January 2025|archive-date=2012-10-06 }}</ref> Rotational forces stabilize the bullet gyroscopically as well as aerodynamically. Any asymmetry in the bullet is largely canceled as it spins. However, a spin rate greater than the optimum value adds more trouble than good, by magnifying the smaller asymmetries or sometimes resulting in the bullet breaking apart in flight. With smooth-bore firearms, a spherical shape is optimal because no matter how the bullet is oriented, its aerodynamics are similar. These unstable bullets tumble erratically and provide only moderate accuracy; however, the aerodynamic shape changed little for centuries. Generally, bullet shapes are a compromise between aerodynamics, interior ballistic necessities, and [[terminal ballistics]] requirements.

Terminal ballistics and [[stopping power]] are aspects of bullet design that affect what happens when a bullet impacts with an object. The outcome of the impact is determined by the composition and density of the target material, the [[Angle of incidence (aerodynamics)|angle of incidence]], and the velocity and physical characteristics of the bullet. Bullets are generally designed to penetrate, deform, or break apart. For a given material and bullet, the strike velocity is the primary factor that determines which outcome is achieved.

Bullet shapes are many and varied. With a mold, bullets can be made at home for reloading ammunition, where local laws allow. Hand-casting, however, is only time- and cost-effective for solid lead bullets. Cast and jacketed bullets are also commercially available from numerous manufacturers for [[handloading]] and are most often more convenient than casting bullets from bulk or scrap lead.

In recent years, manufacturers have introduced bullet designs that rely on computer numerical control (CNC) machining to achieve precise, repeatable geometries not possible with traditional swaging or casting. These designs often feature patented profiles with radial flutes, pressure cavities, or meplat modifications intended to manipulate fluid displacement, induce controlled expansion, or promote bullet tumbling upon impact.

One notable example includes the designs patented by Lehigh Defense, which incorporate machined flutes that channel hydraulic force to create large wound cavities and ensure consistent terminal performance. These bullets are often monolithic in composition and used in hunting and self-defense contexts where expansion and barrier penetration are critical.<ref>{{Cite web |url=https://patentimages.storage.googleapis.com/7a/14/93/8a979c54b3b884/USD748220.pdf |title=Lehigh Defense Bullet Patent |access-date=2025-04-24}}</ref><ref>{{Cite web |url=https://www.fieldandstream.com/guns/lehigh-defense-tipped-xtreme-chaos-bullet-review/ |title=Lehigh Defense Tipped Xtreme Chaos Bullet Review |website=Field & Stream |access-date=2025-04-24}}</ref><ref>{{Cite web |url=https://www.shootingtimes.com/editorial/wringing-out-lehigh-defense-copper-bullets/517818 |title=Wringing Out Lehigh Defense Copper Bullets |website=Shooting Times |access-date=2025-04-24}}</ref>