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April 5th, 2023

Berger Twist Rate Stability Calculator — Optimize Bullet RPM

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.


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.
Permalink Bullets, Brass, Ammo, Competition, Tech Tip No Comments »
April 5th, 2023

Super-Sized Deluxe Shooting Mats from Creedmoor Sports

creedmoor sports Deluxe Long Range Double Mat

New Deluxe Extra-Long Shooting Mat with Extended Sides

Creedmoor Sports now offers a new Deluxe Long Range Shooting Mat with extended right- and left-side wings. This 32″ x 106″ mat was designed with feedback from long-range shooters who needed features not found in conventional shooting mats. The mat is available now for $199.95 at Creedmoor Sports.

Deluxe Long Range Shooting Mat Features
Centrally located, non-slip MegaGripII rubber pad to prevent rear bag from slipping
Increased overall length and width (at 106″ OAL, the mat is 8.8 feet long!)
Side flaps with storage compartments for increased space when shooting
Rear extension flat to keep shooter’s entire body on the mat
Front flap to lessen dirt and debris from muzzle blast

creedmoor sports Deluxe Long Range Double Mat

This roll-up style Deluxe Long Range Shooting Mat has a 1000 denier Cordura Nylon upper with a water-resistant vinyl bottom. Stake pockets and stakes are included to keep the mat in-place on windy days.

Creedmoor Sports Deluxe Long Range Double Mat

creedmoor sports Deluxe Long Range Double Mat

The Deluxe Long Range Double Mat gives shooters more real estate on the firing line. Measuring 56″ x 67″, this double-sized mat features the same construction as conventional Creedmoor Sports mats, but is twice the size. The increased footprint provides increased space for equipment (spotting scope, ammo box, shot log, tablet for electronic target viewing).

This 56″-wide Double Mat can comfortable support two (2) individuals. This has many benefits:

Shooter and spotter can be side-by-side by for improved communication
Mat allows coaching from alongside the shooter
Mat works for Pair Firing in team competitions

creddmoor sports Deluxe Long Range Double Mat

Price for the Deluxe Double Mat (as shown) is $249.95. Or you can order a custom, made-to-order version with various color fabrics for $289.95. This item is hand made to order at the Creedmoor Sports Alabama facility and can take 14-20 business days to ship.

Permalink Competition, Gear Review, New Product No Comments »
April 5th, 2023

Cut-Away View Reveals Complex Interior of Modern Riflescope

Based on its external appearance, a modern riflescope may seem simple. It’s just a tube with two or three knobs on the outside right? Well, looks can be deceiving. Modern variable focal-length optics are complex systems with lots of internal parts. Modern scopes, even ‘budget’ optics, use multiple lens elements to allow variable magnification levels and parallax adjustment.

A few seasons back, we had a chance to look inside a riflescope thanks to a product display from ATK, now called Vista Outdoor, parent of Alliant Powder, CCI, Federal, RCBS, Speer, Weaver Optics. The Weaver engineers sliced open a Weaver Super Slam scope so you can see the internal lens elements plus the elevation and windage controls. We thought readers would like to see the “inner workings” of a typical modern rifle scope, so we snapped some pictures. The sectioned Super Slam scope was mounted inside a Plexiglas case, making it a bit hard to get super-sharp images, but you can still see the multiple lenses and the complex windage and elevation controls.

Check out the details of the focusing and magnification rings near the ocular (eyeball) end of the scope. There is very fine machining and threading to make everything work properly. The ocular lens is the piece of glass that faces the shooter while he aims.

Permalink Optics, Tech Tip No Comments »