Tech Talk

Overview The modern rifle is named for the spiral grooves cut in the barrel which impart a spin to the bullet. Spinning imparts gyroscopic stability, which is what keeps the bullet flying point forward. Longer bullets need to spin faster than shorter bullets to achieve stability. For many years, the relative proportions of bullets haven’t changed much, and so the twist rate of riflings has sort of stagnated around standard values. However in recent times, technology is advancing to the point where higher performance (longer) bullets can be made with greater precision, and so the thoughtful consideration of twist rate and stability is becoming important. [...]

Cartridge Base To Ogive (CBTO) The first half of this article focused on the importance of COAL in terms of SAAMI standards, magazine lengths, etc.  There is another measure of length for loaded ammunition which is highly important to precision. Figure 2. Chamber throat geometry showing the bullet jump to the rifling or lands. Refer back to Figure 2.  Suppose the bullet was seated out of the case to the point where the base of the bullet's nose (ogive) just contacted the beginning of the riflings (the lands) when the bolt was closed.  This bullet seating configuration is referred to as touching the [...]

Many shooters are not aware of the dramatic effects that bullet seating depth can have on the pressure and velocity generated by a rifle cartridge.  COAL is also a variable that can be used to fine tune accuracy.  It's also an important consideration for rifles that need to feed rounds thru a magazine.  In this article, we'll explore the various effects of COAL, and what choices a shooter can make to maximize the effectiveness of their hand loads. Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) Most loading manuals (including the Berger Manual), present loading data according to SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) standards.  [...]

Background In 2009, Berger Bullets introduced G7 BC's for boat tail bullets. For those who are unfamiliar with G7 BCs, it's simply a Ballistic Coefficient referenced to the G7 standard projectile instead of the G1 standard projectile. The G7 standard is a better match for modern long range bullets, so the G7 BC will be more constant over a wide range of velocities compared to a G1 BC. Please refer to article: https://bergerbullets.com/a-better-ballistic-coefficient/ for the complete explanation of the benefits of using G7 BC's. Since 2009, many shooters have realized the benefits of G7 BC's thru more accurate trajectory predictions. The objective of this article [...]