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February 7th, 2018

Stability Calculator — Determine Optimal Barrel Twist Rate

Berger twist rate calculator

With the Berger Southwest Nationals underway this week, we thought we’d steer our readers to a very useful resource, courtesy Berger Bullets. This online Stability Calculator helps shooters determine the optimal twist rate for their choice of projectiles.

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, Reloading No Comments »
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 »
August 6th, 2014

Berger Updates Free Online Bullet Stability Calculator

Berger Bullets has improved its online stability calculator. Tests have shown that bullets can suffer from reduced BC if the bullet rpm (spin rate) is less than optimal, even if barrel twist rate is otherwise fast enough to stabilize bullets in flight. Now, the improved, free Stability Calculator can determine if you need a faster-twist barrel to enjoy the best BC from your bullets.

CLICK HERE for FREE Berger Twist Rate Stability Calculator

By Bryan Litz, Chief Ballistician for Berger Bullets
We’re happy to announce a major upgrade to our Twist Rate Stability Calculator which is free to use on the Berger Bullets webpage. The old stability calculator was pretty basic, and would simply return a gyroscopic stability number based on your bullet, twist rate, and atmospheric conditions. This was used to determine if your barrels twist rate was fast enough to stabilize a particular bullet or not, based on the Gyroscopic Stability Factor (SG) being greater than 1.4.

Berger Bullet Stability Calculator Twist Rate Bryan Litz

Stability and BC — How Bullet RPM Affects Ballistic Coefficients
The new calculator still calculates SG, but also goes much further. In addition to calculating stability, the upgraded calculator can also tell you if your stability level is harming the effective BC of your bullets or not. Extensive testing has proven that bullets fired with stability levels between 1.2 and 1.5 can fly with excellent precision (good groups), but suffer from a depressed BC, sometimes as much as 10%. Shooting the bullets from faster twist rate barrels allows for the bullets to fly better and realize their full BC potential.

Berger Bullet Stability Calculator Twist Rate Bryan Litz

Permalink Bullets, Brass, Ammo, News No Comments »
December 7th, 2012

Berger Bullets Rolls Out Redesigned and Enhanced Website

Report by Jeff Williams, AccurateShooter Correspondent
If you’ve visited BergerBullets.com lately, you’ve noticed that Berger Bullets has completely over-hauled and updated its website. The new website has a very handsome, clean layout. It is also faster to load and much easier to navigate. We give Berger an “A” grade for the new website.

Berger bullets

Berger bulletsOn Berger’s home page you’ll find product descriptions, easy-to-use (smart-phone friendly) product buttons, pull-down menus for all four Berger bullet line-ups, recent news items, plus videos. Click “Links” to access a comprehensive list of reloading resources with a directory of shooting association websites. Click the Berger Bulletin tab to read current product status reports, technical articles, and shooting tips.

Redesigned Bullet Info Tables
The bullet product info pages are much easier to read now. Simple tables display all the bullets of a particular type (hunting, target, varmint, and tactical), organized by caliber and weight within calibers. You’ll find BOTH G1 model and G7 model Ballistics coefficients (BCs) for all the bullets in the tables, and recommended twist rates are listed.

Berger bullets

Berger Twist-Rate Stability Calculator
The new Berger website also offers 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 very cool tool tells you if your chosen bullet will really stabilize in your barrel. LIVE DEMO BELOW — Just enter values in the data boxes and click “Calculate SG”.

Permalink Bullets, Brass, Ammo, News 1 Comment »