September 23rd, 2018

Bullet Geometry: Tangent, Secant, and Hybrid Ogives Explained

secant tangent hybrid ogive Bryan Litz Applied ballistices 200X Berger Hybrid bullet, .308 30 Caliber

In discussions of ballistics, you’ll see references to “tangent”, “secant”, and “hybrid” 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, secant, and hybrid ogive bullet designs, to help you understand the characteristics of these three basic 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.

hybrid bullet

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.”

Bryan Litz Explains Hybrid Design and Optimal Hybrid Seating Depths

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.

Story sourced by Edlongrange.
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September 23rd, 2018

Mini-Target Playing Cards — Great for “Wallet Groups”

Bell & Carlson stocks shooting card Shoot'n Aces playing target cards

Want to show off some groups you’ve shot? Or keep a handy pack of mini-targets in your range kit? Then check out this unique product from stockmaker Bell & Carlson. Shoot’n Aces cards feature a 1-inch black square aiming box with a 1/2-inch inner square. These cards are normal poker-playing-card size, 3.5″ high x 2.5″ wide (89 × 64 mm). Shoot’n Aces cards come 56 to a pack. Carry a few extras in your wallet or a pack in your vehicle glove compartment and you’ll always have a precision target to shoot at the range. Cards can be stapled or taped to target stands.

Bell & Carlson stocks shooting card Shoot'n Aces playing target cards

Bell & Carlson stocks shooting card Shoot'n Aces playing target cardsSniper Central says these cards work well as targets: “The bold square is easy to pick up with the inner white portion making a nice aiming point. The material of the cards is the same as normal playing cards and the bullets make a very nice hole when passing through.” The sharp edges of the bullet holes makes it easy to measure group sizes with precision.

Each pack of Shoot’n Aces contains 56 premium-quality target cards. If you want some, order Bell & Carlson item SA-2006. This is a set of four (4) card-packs with 56 cards per pack (224 cards total) priced at $20.00 (i.e. $5.00 per pack).

Product Tip from EdLongrange.
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