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November 8th, 2024

Bullets Spinning Fast Enough? Use Twist Rate Stability Calculator

Berger twist rate calculator

Berger Twist-Rate Stability Calculator
Berger twist rate calculatorOn 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 (3rd Ed.), 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.
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November 8th, 2024

Expert Advice on How to Set Up Slings for Competition

Dennis DeMille Creedmoor Sports Rifle Sling video training set-up
Dennis DeMille shows a young competitor at the CMP Western Games how to adjust his leather sling.

If you want to learn more about setting up your sling properly for position shooting, here are some tips from Dennis DeMille, a past Service Rifle Champion. Dennis explains how to choose a sling, and how to adjust it to fit properly.

Dennis DeMille High PowerThe Benefits of Dry-Fire Training
Once you know how to set up your sling properly, you’ll want to practice. Dennis DeMille stresses the importance of dry-fire practice with sling and shooting coat. Dry-Fire training is essential to the sling disciplines. Dennis DeMille, a national Service Rifle Champion, told us that, for every minute he spent in actual competition, he would spend hours practicing without ammunition. While in the USMC, Dennis would practice in the barracks, working on his hold and dry-firing:

“The most important thing is to spend time off the range practicing. Most of what I learned as a High Power shooter I learned without ammunition — just spending time dry firing and doing holding exercises. Holding exercises will really identify the weak parts of your position. The primary purpose of dry firing is to get you used to shooting an empty rifle. If you can shoot a loaded rifle the same way you shoot an empty rifle then eventually you will become a High Master.”

Brandon Green Sling shooting
SFC Brandon Green, 3-Time Nat’l High Power Champion. Brandon, one of the nation’s best “hard-holders”, demonstrates proper use of sling in prone position.

Setting-Up a Leather Service Rifle Sling for Competition

So you made the mistake of disassembling your leather service rifle sling, or are intimidated about how to use one? In this Creedmoor Sports InfoZone video, former Creedmoor G.M. Dennis DeMille explains how to set up and use a sling. The covers the basics — Dennis starts with a totally disassembled leather service rifle sling and shows you how to set it up properly.

Tip: “Many shooters shy away from using a leather sling because they have never been taught how to use one. That’s unfortunate. In my opinion a leather sling offers more support than a web sling, which is important when competing with the heavier than normal rifles.”

Configuring the Sling for the Standing (Offhand) Position
In this second in a series of Creedmoor InfoZone videos on the setup and use of the leather service rifle sling, Dennis DeMille details how to configure and best utilize the leather service rifle sling while shooting from the standing position.

Tip: “Putting the Frogs in different hole will change the amount of added elevation a sling provides.”

Looking at Sling Types — Comparing the Features
In this video Dennis showcases a large variety of shooting slings. He explains the strong points of each type so you can choose the sling best suited to your discipline and shooting style.

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