October 28th, 2014

Ogive No Jive — Litz Explains Tangent, Secant, and Hybrid Ogives

Secant and Tangent Ogive Bryan LitzIn discussions of ballistics, you’ll see references to “tangent” and “secant” bullet shapes. We know that, for many readers, these terms can be confusing. To add to the confusion, bullet makers don’t always identify their projectiles as secant or tangent designs. This article provides a basic explanation of tangent and secant designs, to help you understand the characteristics of both bullet shapes.

Tangent vs. Secant vs. Hybrid
Most match bullets produced today use a tangent ogive profile, but the modern VLD-style bullets employ a secant profile. To further complicate matters, the latest generation of “Hybrid” projectiles from Berger Bullets feature a blended secant + tangent profile to combine the best qualities of both nose shapes. The secant section provides reduced drag, while the tangent section makes the bullet easier to tune, i.e. less sensitive to bullet seating depth position.

Berger Bullets ballistician Bryan Litz explains tangent and secant bullet ogive designs in a glossary section of his Applied Ballistics website, which we reprint below. Bryan then explains how tangent and secant profiles can be combined in a “hybrid” design.

How Bullet Ogive Curves are Defined
While the term “ogive” is often used to describe the particular point on the bullet where the curve reaches full bullet diameter, in fact the “ogive” properly refers to the entire curve of the bullet from the tip to the full-diameter straight section — the shank. Understanding then, that the ogive is a curve, how is that curve described?

LITZ: The ogive of a bullet is usually characterized by the length of its radius. This radius is often given in calibers instead of inches. For example, an 8 ogive 6mm bullet has an ogive that is a segment of a circular arc with a radius of 8*.243 = 1.952”. A .30-caliber bullet with an 8 ogive will be proportionally the same as the 8 ogive 6mm bullet, but the actual radius will be 2.464” for the .30 caliber bullet.

For a given nose length, if an ogive is perfectly tangent, it will have a very specific radius. Any radius longer than that will cause the ogive to be secant. Secant ogives can range from very mild (short radius) to very aggressive (long radius). The drag of a secant ogive is minimized when its radius is twice as long as a tangent ogive radius. In other words, if a tangent ogive has an 8 caliber radius, then the longest practical secant ogive radius is 16 calibers long for a given nose length.”

hybrid bullet

Ogive Metrics and Rt/R Ratio
LITZ: There is a number that’s used to quantify how secant an ogive is. The metric is known as the Rt/R ratio and it’s the ratio of the tangent ogive radius to the actual ogive radius for a given bullet. In the above example, the 16 caliber ogive would have an Rt/R ratio of 0.5. The number 0.5 is therefore the lowest practical value for the Rt/R ratio, and represents the minimum drag ogive for a given length. An ogive that’s perfectly tangent will have an Rt/R ratio of 1.0. Most ogives are in between an Rt/R of 1.0 and 0.5. The dimensioned drawings at the end of my Applied Ballistics book provide the bullets ogive radius in calibers, as well as the Rt/R ratio. In short, the Rt/R ratio is simply a measure of how secant an ogive is. 1.0 is not secant at all, 0.5 is as secant as it gets.

Berger Hybrid bullet, .308 30 CaliberHybrid Bullet Design — Best of Both Worlds?
Bryan Litz has developed a number of modern “Hybrid” design bullets for Berger. The objective of Bryan’s design work has been to achieve a very low drag design that is also “not finicky”. Normal (non-hybrid) secant designs, such as the Berger 105gr VLD, deliver very impressive BC values, but the bullets can be sensitive to seating depth. Montana’s Tom Mousel has set world records with the Berger 105gr VLD in his 6mm Dasher, but he tells us “seating depth is critical to the best accuracy”. Tom says a mere .003″ seating depth change “makes a difference”. In an effort to produce more forgiving high-BC bullets, Bryan Litz developed the hybrid tangent/secant bullet shape.

Bryan Litz Explains Hybrid Design and Optimal Hybrid Seating Depths

Story sourced by Edlongrange.

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October 28th, 2014

Bushnell Brawl Featured on Shooting USA This Week

Bushnell Brawl Shooting USA

This Wednesday, October 29, Shooting USA TV features the Bushnell Brawl, a tactical competition that draws top long-range shooters from the military, law enforcement and the civilian shooting communities. The match is held at the famed Rifles Only range in Kingsville, Texas. The Brawl is a one-of-a-kind physical and mental challenge — 20 events test each shooter’s ability to read wind, figure ballistics, and adapt to difficult shooting scenarios. And, each year, the competition proves to be even more challenging. There is even a helicopter stage.

Bushnell Rifles Only Brawl 2014 Shooting USA

“Whenever the difficulty ramps up, they step up, and we’ve seen it for the last fifteen years doing matches,” says Rifles Only Director, Jacob Bynum. “Ramp up the difficulty, quality goes up.”

The signature event is Trench Warfare, where each competitor gets a chance to shoot from a helicopter before running to the trench. Competitors also shoot from the tower, where shots are out to 1,000 yards. Not all events are shot over long distance. The Five Dot Drill and Know Your Limit on paper are shot inside 100 yards.

Watch Preview of Bushnell Brawl

Shooting USA Television Wednesday Showtimes:
Eastern Time – 3:30 PM, 9:00 PM, 12:00 M
Central Time – 2:30 PM, 8:00 PM, 11:00 PM
Mountain Time – 1:30 PM, 7:00 PM, 10:00 PM
Pacific Time – 12:30 PM, 6:00 PM, 9:00 PM

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