July 31st, 2016

Berger Bullets Twist Rate Stability Calculator

Berger twist rate calculator

Berger twist rate calculatorBerger Twist-Rate Stability Calculator
On the Berger Bullets website you’ll find a handy Twist-Rate Stability Calculator that predicts your gyroscopic stability factor (SG) based on mulitiple variables: velocity, bullet length, bullet weight, barrel twist rate, ambient temperature, and altitude. This cool tool tells you if your chosen bullet will really stabilize in your barrel.


CLICK HERE to Go to TWIST RATE CALCULATOR PAGE

How to Use Berger’s Twist Rate Calculator
Using the Twist Rate Calculator is simple. Just enter the bullet DIAMETER (e.g. .264), bullet WEIGHT (in grains), and bullet overall LENGTH (in inches). On its website, Berger conveniently provides this info for all its bullet types. For other brands, we suggest you weigh three examples of your chosen bullet, and also measure the length on three samples. Then use the average weight and length of the three. To calculate bullet stability, simply enter your bullet data (along with observed Muzzle Velocity, outside Temperature, and Altitude) and click “Calculate SG”. Try different twist rate numbers (and recalculate) until you get an SG value of 1.4 (or higher).

Gyroscopic Stability (SG) and Twist Rate
Berger’s Twist Rate Calculator provides a predicted stability value called “SG” (for “Gyroscopic Stability”). This indicates the Gyroscopic Stability applied to the bullet by spin. This number is derived from the basic equation: SG = (rigidity of the spinning mass)/(overturning aerodynamic torque).

Berger twist rate calculator

If you have an SG under 1.0, your bullet is predicted not to stabilize. If you have between 1.0 and 1.1 SG, your bullet may or may not stabilize. If you have an SG greater than 1.1, your bullet should stabilize under optimal conditions, but stabilization might not be adequate when temperature, altitude, or other variables are less-than-optimal. That’s why Berger normally recommends at least 1.5 SG to get out of the “Marginal Stability” zone.

In his book Applied Ballistics For Long-Range Shooting, Bryan Litz (Berger Ballistician) recommends at least a 1.4 SG rating when selecting a barrel twist for a particular bullet. This gives you a safety margin for shooting under various conditions, such as higher or lower altitudes or temperatures.

Story idea from EdLongrange. We welcome reader submissions.
Permalink Bullets, Brass, Ammo, Tech Tip 1 Comment »
July 31st, 2016

A Shotgun Fit for Royalty — Westley Richards 12 Gauge SxS

Westley Richards 12 gauge shotgun Princess Diana Spencer Princed Charles wedding shotgun gift

Here is some eye candy for fans of fine firearms. Made for the 1981 nuptials of Lady Diana Spencer and HRH Prince Charles, this Westley Richards & Co. side-by-side, 12 gauge shotgun was engraved by the Brown Brothers with gold crests and floral accents. The British royal seal and other heraldic emblems of the couple are included in the decoration. This amazing piece is now in the NRA Museum Collection.

Westley Richards 12 gauge shotgun Princess Diana Spencer Princed Charles wedding shotgun gift

Princess Diana’s Westley & Richards Shotgun
It’s not an uncommon practice for people who like firearms to be given one for a big occasion, such as a graduation or a birthday. Today’s GOTD was given to a very special person on a very special occasion that took place 35 years ago today. This 12 gauge Westley Richards side-by-side shotgun was given to Lady Diana Spencer when she married Prince Charles on July 29, 1981. The gun was engraved by the Brown Brothers — Paul and Alan — and features a variety of artistic elements, including the royal seal and the couple’s wedding date.

Westley Richards 12 gauge shotgun Princess Diana Spencer Princed Charles wedding shotgun gift

Westley Richards 12 gauge shotgun Princess Diana Spencer Princed Charles wedding shotgun gift

Photos courtesy NRA National Firearms Museum, www.nramuseum.org.

Permalink Gunsmithing, Hunting/Varminting No Comments »