Very-low-drag bullet
{{Short description|Type of bullet}}
Image:VLD-bullet.jpg alloy (such as gilding metal or cupronickel)]]
A very-low-drag bullet (VLD) is primarily a small arms ballistics development of the 1980s–1990s, driven by the design objective of bullets with higher degrees of accuracy and kinetic efficiency, especially at extended ranges. To achieve this, the projectile must minimize air resistance in flight. Usage has been greatest from military snipers and long-range target shooters, including F-class and benchrest competitors, but hunters have also benefited. Most VLD bullets are used in rifles. VLD bullets typically have a G1 ballistic coefficient greater than 0.5, although the threshold is undefined.
Bullets with a lower drag coefficient decelerate less rapidly. A low drag coefficient flattens the projectile's trajectory and also markedly decreases the lateral drift caused by crosswinds. The higher velocity of bullets with low drag coefficients means they retain more kinetic energy.{{cite web |url=https://www.fieldandstream.com/blogs/the-gun-nuts/understanding-vld-bullets |title=Understanding VLD Bullets |last=Petzal |first=David E. |date=7 July 2014 |publisher=Field & Stream |access-date=13 June 2018 }}
Development
VLD bullets are long and heavy for their diameter, to achieve a high sectional density. Development of VLD bullets has focused on reducing a form factor defined as the sectional density divided by the ballistic coefficient.{{cite web |url=http://www.appliedballisticsllc.com/Articles/ABDOC2.3%20-%20Form%20Factors%20A%20Usefull%20Tool.pdf |title=Form Factors: A Useful analysis Tool |last=Litz |first=Bryan |publisher=Applied Ballistics |access-date=13 June 2018 }} Form factor can be minimized by:
- bullet nose design incorporating a secant ogive, tangent ogive, Von Kármán ogive or Sears-Haack profile{{cite web |url=http://www.bergerbullets.com/information/line-and-designs/ |title=Lines And Designs |publisher=Berger Bullets |access-date=13 June 2018 }}
- the use of tapered bullet heels, also known as boat-tails
- a cavity or hollow in the bullet nose (hollow point) to reduce weight while shifting the projectile's centre of gravity rearwards to improve stability with concentric and coincident centre of pressure and centre of mass{{Cn|date=January 2021}}
The resulting projectile should be streamlined for easier passage through the air. Consistency in bullet production, allied to consistency in the assembly of cartridges (quality control) should give excellent shot-to-shot consistency.{{Cn|date=January 2021}}
The principles of bullet design and flight are classically set out in Franklin Ware Mann's The Bullet's Flight From Powder to Target: Ballistics of Small Arms.* Mann, F.W.: The Bullet's Flight From Powder to Target: Ballistics of Small Arms (1942 and other reprints)
Mono-metal designs
Machining mono-metal bullets (coreless bullets made of one single metal) offers bullet designers the freedom to design slender, aerodynamically efficient shapes that cannot be produced with more traditional bullet production methods. Professional quality control during and after production is needed to guarantee the bullets' consistency and accuracy. Mono-metal solid bullets are more expensive than traditional jacketed hollow point boat-tail VLD bullets.{{Cn|date=January 2021}}
To reduce damage to the employed barrel and increase muzzle velocity, some modern mono-metal VLD bullets are bore-riding bullets, in which thin driving bands are the only parts that are etched by a barrel's lands. The use of driving bands originates from artillery shells and to use these driving bands correctly requires projectiles and barrels to be precision-fitted to each other.{{Cn|date=January 2021}}
Mono-metal VLD bullets are normally machined from solid bars of highly-machinable metals or alloys using CNC lathes. Common materials include UNS C36000 free-cutting brass, lead-free brass,[http://www.wieland.de/commonmedia/content/media/en/datenbltter/datenbltterz/Da_z_Ecobrass_SW1_08.pdf Wieland-SW1 lead-free special brass]{{dead link|date=July 2016 |bot=InternetArchiveBot |fix-attempted=yes }} oxygen-free copper and other highly machinable alloys of copper, nickel, and tellurium.{{Cn|date=January 2021}}
See also
References
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External links
- [http://www.jacksonrifles.com/vldvarmints.htm VLD bullets] on long-range varmint hunting
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