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August 4th, 2021

Bullet Geometry Basics: Tangent, Secant, and Hybrid Ogives

secant tangent hybrid ogive Bryan Litz Applied ballistics 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.

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July 31st, 2021

Video Showcase: Wisdom from Keith Glasscock

Keith Glasscock winning wind youtube channel f-Class f-Open ES SD loading

Keith Glasscock is one of America’s greatest F-Class shooters, as well as a highly respected wind coach. A High Master, Keith finished second overall at the 2021 NRA F-Class Long Range Championship in F-Open division. He also finished second at the 2020 Nationals, tied with F-Open winner Pat Scully on points, but with fewer Xs. And he took second also at the 2019 Nationals. His consistency is unrivaled, which means he definitely knows the secrets of long range wind calling and loading ultra-accurate ammo.

Keith has a popular YouTube Channel with new content every week. On Keith’s Winning in the Wind channel, Keith offers 60+ informative videos on a wide range of topics including wind reading, reloading, component selection, load development, and training. For today’s Video Showcase, we offer four of our favorite Keith Glasscock videos. Each video has important points that can benefit any competitive rifle shooter, whether you shoot in local 100-yard fun matches or compete at the National Level in F-Class, LR Benchrest, Palma, or High Power.

How to Find (and Fine-Tune) Seating Depth

This is Keith’s most popular video. Keith definitely knows how to maximize accuracy by finding the optimal seating depth for each particular barrel. He is achieving groups in the high Ones for three shots. That would be good for a short-range benchrest cartridge, but Keith is achieving that with a .284 Winchester which has much more recoil. If you shoot F-TR or F-Open or even PRS, you should watch this video.

How to Lower your ES/SD and Reduce Vertical at Long Range

This is Keith’s first video in a series on how to improve long range groups, precision, and accuracy by reducing velocity Extreme Spread (ES) and Standard Deviation (SD). To achieve the lowest ES you need to look at multiple processes, including precision powder weighing, careful seating, brass annealing, and primer selection. Another factor is bullet selection. Not all bullets of the same nominal caliber and weight class have exactly the same bullet diameter or shape. Sometimes you can get better accuracy AND lower ES by trying a different brand of bullet. We have found bullet diameters, of the same stated caliber, can vary by up to .0008″ (eight ten-thousandths). Some barrels like the fatter bullets, while other barrels may favor the skinny bullets.

How to Find Bullet-to-Rifling Touch Point

Before you even start to load for a new rifle you need to know the point at which the bullet in a loaded round will first touch the rifling. (This will be a base to ogive measurement on your round). Beyond that point you are “in the lands”. If you load shorter than that base-to-ogive length you are “jumping” your bullets. Some cartridge/bullet combos typically shoot best in the lands, while with other bullets and cartridges, jumping is the way to go. Additionally, with some disciplines it is wise to jump your bullets since you may have to unload a chambered round while on the firing line. In this video Keith shows a number of methods to determine “length to lands” with repeatable precision.

Field Test and Review of SEB Mini-X Coaxial Front Rest

While gear reviews are not the primary focus of Keith’s YouTube Channel, Keith does talk about products he likes and uses. In this video. Keith reviews the SEB Mini-X, the newest coaxial tripod rest from SEB Rests. The Mini-X offers fast, precise windage and elevation adjustment with the joystick control. The unit is much easier to pack and transport than a large, heavy front rest such as a SEB NEO or Farley. The latest Mini-X also has upgraded foot controls that make it easier to level the rest on uneven ground. For more info, see our SEB Mini-X Report.

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June 4th, 2021

How Cartridge Overall Length (COAL) Affects Pressure & Velocity

Berger Bullets COAL length cartridge

Figure 1. When the bullet is seated farther out of the case, there is more volume available for powder. This enables the cartridge to generate higher muzzle velocity with the same pressure.

Berger Bullets COAL length cartridgeEffects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 1
by Bryan Litz for Berger Bullets.
Many shooters are not aware of the dramatic effects that bullet seating depth can have on the pressure and velocity generated by a rifle cartridge. Cartridge Overall Length (COAL) is also a variable that can be used to fine-tune accuracy. It’s also an important consideration for rifles that need to feed rounds through a magazine. In this article, we’ll explore the various effects of COAL, and what choices a shooter can make to maximize the effectiveness of their hand loads.

Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI)
Most loading manuals (including the Berger Manual), present loading data according to SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) standards. SAAMI provides max pressure, COAL and many other specifications for commercial cartridges so that rifle makers, ammo makers, and hand loaders can standardize their products so they all work together. As we’ll see later in this article, these SAAMI standards are in many cases outdated and can dramatically restrict the performance potential of a cartridge.

Bullet seating depth is an important variable in the accuracy equation. In many cases, the SAAMI-specified COAL is shorter than what a hand loader wants to load their rounds to for accuracy purposes. In the case where a hand loader seats the bullets longer than SAAMI specified COAL, there are some internal ballistic effects that take place which are important to understand.

Effects of Seating Depth / COAL on Pressure and Velocity
The primary effect of loading a cartridge long is that it leaves more internal volume inside the cartridge. This extra internal volume has a well known effect; for a given powder charge, there will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you have to use more powder to achieve the same pressure and velocity when the bullet is seated out long. In fact, the extra powder you can add to a cartridge with the bullet seated long will allow you to achieve greater velocity at the same pressure than a cartridge with a bullet seated short.

When you think about it, it makes good sense. After all, when you seat the bullet out longer and leave more internal case volume for powder, you’re effectively making the cartridge into a bigger cartridge by increasing the size of the combustion chamber. Figure 1 illustrates the extra volume that’s available for powder when the bullet is seated out long.

Before concluding that it’s a good idea to start seating your bullets longer than SAAMI spec length, there are a few things to consider.

Geometry of a Chamber Throat
The chamber in a rifle will have a certain throat length which will dictate how long a bullet can be loaded. The throat is the forward portion of the chamber that has no rifling. The portion of the bullet’s bearing surface that projects out of the case occupies the throat (see Figure 2).

Berger Bullets COAL length cartridge

The length of the throat determines how much of the bullet can stick out of the case. When a cartridge is chambered and the bullet encounters the beginning of the rifling, known as the lands, it’s met with hard resistance. This COAL marks the maximum length that a bullet can be seated. When a bullet is seated out to contact the lands, its initial forward motion during ignition is immediately resisted by an engraving force.

Seating a bullet against the lands causes pressures to be elevated noticeably higher than if the bullet were seated just a few thousandths of an inch off the lands.

A very common practice in precision reloading is to establish the COAL for a bullet that’s seated to touch the lands. This is a reference length that the hand loader works from when searching for the optimal seating depth for precision. Many times, the best seating depth is with the bullet touching or very near the lands. However, in some rifles, the best seating depth might be 0.100″ or more off the lands. This is simply a variable the hand loader uses to tune the precision of a rifle.

CLICK HERE to Read Full Article with More Info

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March 24th, 2021

Accuracy One Seating Depth Comparator Review

Accuracy One Seating Depth Comparator gauge ogive shoulder measure reloading ammunition case

Looking for a faster, easier, and more accurate way to measure bullet positions on your loaded rounds? Check out the Accuracy One Seating Depth Comparator. This unique tool provides a shoulder-to-ogive measurement instead of the traditional cartridge base-to-ogive measurement. The Accuracy One Comparator just might work for you. This unique tool allows a very rapid and secure measurement that provides a precise determination of the bullet seating depth in the case.

Accuracy One Seating Depth Comparator

Product Review by F-Class John
You probably check your loaded ammo by measuring cartridge base to ogive, but have you ever considered there may be a better way? Curt at Accuracy One has considered the question, and after exhaustive research and testing he created the Accuracy One Seating Depth Comparator. As opposed to looking for a base to ogive measurement, this tool measures from the shoulder to ogive, which is arguably the more repeatable number when it comes to accuracy.

Click Arrow to Watch Video Tool Review

As Curt explains, “Well, when you fire a chambered cartridge, the strike from the firing pin first pushes the cartridge forward until it bottoms against the shoulder. The primer is then ignited. What this means is that your seated bullet depth consistency can more accurately be gauged using the dimension from shoulder to ogive. Using this dimension, you effectively eliminate any small variances in your sized case length from the equation”. As a result, it made sense that when he was designing the measurement tool his goal was to create a universal insert that allowed a user a quick, easy, accurate and repeatable process that measures from mid-shoulder to ogive.

Accuracy One Seating Depth Comparator gauge ogive shoulder measure reloading ammunition case

The comparator fits cartridges from .22 to .30 Caliber with 0.400″ and larger shoulder diameters. The tool fits so many bullet sizes because of the specific taper that Curt developed. This ensures that any caliber in that range makes good contact along the ogive. As I used this tool and talked to people about it, I kept getting skeptical comments with people asking how it could measure the ogive on that many calibers accurately. I had to remind them that the ogive is not a single point on the bullet but in fact the entire curve from the tip of the bullet to the point it straightens out. As a result, it’s only important that the tool you use is consistent in what point along the ogive it measures and that’s where the Accuracy One Seating Depth Comparator shines. According to Curt, he went through countless iterations on his design until he was able to accurately and repeatably measure all those calibers (.22 to .30).

Accuracy One Seating Depth Comparator gauge ogive shoulder measure reloading ammunition case

How to Use the Accuracy One Seating Depth Comparator
Using the comparator is simple. There are alternative methods. The easiest way is to simply zero the indicator, insert a loaded round, note the measurement and compare any future rounds against it for variation. An alternative to this is a method I use. I insert a loaded round and then zero the indicator. This allows you to see the exact variation without mental math (and frankly it’s faster this way). I also use this method to sort loaded rounds for matches in order from shortest to longest ensuring that rounds that measure the same are fired together.

Bonus Option — Measuring Length to Lands with Tool
Another great use for this Accuracy One comparator is to take my initial depth to lands. This helps ensure my seating depth was properly set. Using a case with very light neck tension, I load a bullet, and with a stripped bolt I load and close it. Then I can remove the round and take a measurement, zero the indicator and make a note of it in my book. After that the comparator will remember the new zero until it’s zeroed again and if that happens by accident, I can always reference the number that my round measured and pull on the indicator stem until that number is found and then zero it again. I found this entire process fast, easy and repeatable as I loaded rounds and needed to check for any seating depth variance.

Tool Pricing:
Seating Depth Comparator without Indicator: $65.00
Seating Depth Comparator with Indicator: $115.00
Gauge Stand: $47.00

Accuracy One Seating Depth Comparator gauge ogive shoulder measure reloading ammunition casePurchase Options
You can buy the tool with or without an Digital Indicator. Accuracy One also makes a Primer Depth Gauge. Both Accuracy One tools employ the same digital indicator. This helps save money as you can order the comparator alone if you already have one (either from another Accuracy Tool or another tool).

The Accuracy One Seating Depth Comparator is essentially the same size as the Accuracy One Primer Depth Gauge, so you can even utilize Accuracy One’s primer gauge storage case. There is also an optional stand that I HIGHLY RECOMMEND as it can hold either the seating depth OR primer gauge, making for amazingly simple one-handed operation while you’re loading.

CONCLUSION — Tool Is Precise, Repeatable, and Fast
Overall, this tool left me feeling confident in my depth setting and I found it quick and easy compared to past methods. At the end of the day there are several ways to skin the proverbial cat when it comes to measuring seating depth. But if you’re looking for what just might be the most accurate, consistent and speediest method, give the Accuracy One Seating Depth Comparator a try.

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October 9th, 2020

Good Resource for Handloaders Who Want to Make Better Ammo

Glen Zediker Competition Reloading bookForum member Danny Reever and this Editor have discussed how novice reloaders can struggle with the fine points of reloading, making errors in seating depth, neck-bushing choice, or sizing their cases. We agreed that a good resource covering more than “Reloading Basics” is sorely needed. Danny reminded me that Glen Zediker’s excellent Handloading for Competition book has been available since 2002. Danny says this may still be the best guide in print for those getting started in precision reloading, though the book is not without flaws.

Danny observed: “I consider this still the best book out there on the subject. I’ve bought a lot of other books only to be sorely disappointed after spending $30-$40 of my hard-earned cash. This book is not one of those! I’ve read and re-read Zediker’s treatise at least four times and refer to it often for advice while reloading. My number one suggestion for those who buy the book is to sit down with a highlighter and read it cover to cover. It’s well-written with a bit of humor and it is not boring.”

Extremely comprehensive, Zediker’s book covers nearly all of the key factors involved in accurate reloading: case sorting, brass prep, load development, neck-sizing, full-length sizing, bushing selection/use, tool selection, priming, powder measurement, and bullet seating. The book also explains how to test and evaluate your ammo, and how to monitor and interpret pressure signs.

There are many “must-read” sections in Zediker’s book, according to Danny: “The section beginning on page 161 dealing with concentricity (and how to achieve it) is excellent. Likewise the Load Limits section discussing pressures offers very valuable advice and info. You should also read Zediker’s commentaries about load testing, powders (burn characteristics etc.), and the effects of temperature.”

Zediker competition reloading book

CLICK HERE to view book contents and sample pages.

Zediker has conveniently provided a detailed summary of his book on the web, complete with table of contents, sample pages (PDF format), and dozens of illustrations. Shown above is just one small section that covers ejectors.

Overall, we recommend Glen Zediker’s Handloading for Competition, though the book definitely could use some updating. Danny says: “Plunk down the [money] and buy this book, you won’t be sorry.” Zediker’s book is available from Amazon.com ($34.99), Midsouth Shooters ($33.49), and Zediker Publishing ($36.95).

Permalink Gear Review, Reloading, Tech Tip 1 Comment »
December 10th, 2019

How Changes in Cartridge OAL Can Alter Pressure and Velocity

Berger Bullets COAL length cartridge

Figure 1. When the bullet is seated farther out of the case, there is more volume available for powder. This enables the cartridge to generate higher muzzle velocity with the same pressure.

Berger Bullets COAL length cartridgeEffects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 1
by Bryan Litz for Berger Bullets.
Many shooters are not aware of the dramatic effects that bullet seating depth can have on the pressure and velocity generated by a rifle cartridge. Cartridge Overall Length (COAL) is also a variable that can be used to fine-tune accuracy. It’s also an important consideration for rifles that need to feed rounds through a magazine. In this article, we’ll explore the various effects of COAL, and what choices a shooter can make to maximize the effectiveness of their hand loads.

Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI)
Most loading manuals (including the Berger Manual), present loading data according to SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) standards. SAAMI provides max pressure, COAL and many other specifications for commercial cartridges so that rifle makers, ammo makers, and hand loaders can standardize their products so they all work together. As we’ll see later in this article, these SAAMI standards are in many cases outdated and can dramatically restrict the performance potential of a cartridge.

Bullet seating depth is an important variable in the accuracy equation. In many cases, the SAAMI-specified COAL is shorter than what a hand loader wants to load their rounds to for accuracy purposes. In the case where a hand loader seats the bullets longer than SAAMI specified COAL, there are some internal ballistic effects that take place which are important to understand.

Effects of Seating Depth / COAL on Pressure and Velocity
The primary effect of loading a cartridge long is that it leaves more internal volume inside the cartridge. This extra internal volume has a well known effect; for a given powder charge, there will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you have to use more powder to achieve the same pressure and velocity when the bullet is seated out long. In fact, the extra powder you can add to a cartridge with the bullet seated long will allow you to achieve greater velocity at the same pressure than a cartridge with a bullet seated short.

When you think about it, it makes good sense. After all, when you seat the bullet out longer and leave more internal case volume for powder, you’re effectively making the cartridge into a bigger cartridge by increasing the size of the combustion chamber. Figure 1 illustrates the extra volume that’s available for powder when the bullet is seated out long.

Before concluding that it’s a good idea to start seating your bullets longer than SAAMI spec length, there are a few things to consider.

Geometry of a Chamber Throat
The chamber in a rifle will have a certain throat length which will dictate how long a bullet can be loaded. The throat is the forward portion of the chamber that has no rifling. The portion of the bullet’s bearing surface that projects out of the case occupies the throat (see Figure 2).

Berger Bullets COAL length cartridge

The length of the throat determines how much of the bullet can stick out of the case. When a cartridge is chambered and the bullet encounters the beginning of the rifling, known as the lands, it’s met with hard resistance. This COAL marks the maximum length that a bullet can be seated. When a bullet is seated out to contact the lands, its initial forward motion during ignition is immediately resisted by an engraving force.

Seating a bullet against the lands causes pressures to be elevated noticeably higher than if the bullet were seated just a few thousandths of an inch off the lands.

A very common practice in precision reloading is to establish the COAL for a bullet that’s seated to touch the lands. This is a reference length that the hand loader works from when searching for the optimal seating depth for precision. Many times, the best seating depth is with the bullet touching or very near the lands. However, in some rifles, the best seating depth might be 0.100″ or more off the lands. This is simply a variable the hand loader uses to tune the precision of a rifle.

CLICK HERE to Read Full Article with More Info

Article sourced by EdLongrange. We welcome tips from readers.
Permalink Bullets, Brass, Ammo, Reloading 2 Comments »
November 1st, 2019

Ogives, Meplats, Boat-Tails and Other Bullet Design Elements

Bullet Design Zediker

Noted gun writer Glen Zediker (author of Top Grade Ammo), regularly contributes tech articles to the Midsouth Shooters Blog. One of Glen’s Midsouth Blog articles covers Bullet Design. We suggest you read the article — even seasoned hand-loaders will learn a few things about projectile properties (and how to choose the right bullet design for your needs). Glen also wrote a recent Blog article on cartridge pressure signs, linked below

Read Zediker Bullet Design Article | Read Zediker Pressure Signs Article

Glen explains: “A ‘match’ bullet’s job is to perforate a piece of paper. A bullet designed for varmint hunting, on the other hand, is designed to produce explosive impact, and one for larger game hunting strives to strike a balance between expansion and penetration. However! No matter how it’s built inside, there are universal elements of any bullet design, and those are found on the outside.”

Bullet Design Zediker

In his article, Glen identifies the key elements of a bullet and explains how they are defined: “Base, that’s the bottom; boat-tail, or not (flat-base); shank, portion of full-caliber diameter; ogive, the sloping ‘nosecone'; tip, either open or closed (open it’s called the ‘meplat’). The shape of the ogive and the first point of ‘major diameter’ are extremely influential elements. The first point of major diameter can vary from barrel brand to barrel brand because it’s the point on the bullet that coincides with land diameter in the barrel — the first point that will actually contact the barrel as the bullet moves forward. When there’s a cartridge sitting in the rifle chamber, the distance or gap between the first point of major diameter and the lands is called ‘jump’, and, usually, the less there is the better.”

Bullet Design Zediker

Ogives Analyzed — Tangent vs. Secant Bullet Designs
Glen notes that bullet designs reflect secant or tangent profiles, or a combination of both: “The two essential profiles a bullet can take are ‘secant’ and ‘tangent’. This refers to the shape of the ogive. A tangent is a more rounded, gradual flow toward the tip, while a secant is a more radical step-in, more like a spike. Secants fly with less resistance (less aerodynamic drag), but tangents are [often] more tolerant of jump [or to put it another way, less sensitive to seating depth variations].”

Glen adds: “Ogives are measured in ‘calibers’. That’s pretty simple: an 8-caliber ogive describes an arc that’s 8 times caliber diameter; a 12-caliber is based on a circle that’s 12 times the caliber. The 8 will be a smaller circle than the 12, so, an 8-caliber ogive is more ‘blunt’ or rounded. Bullets with lower-caliber ogives are more tolerant of jump and (usually) shoot better, easier. Higher-caliber ogives [generally] fly better, farther. This is an important component in the ‘high-BC’ designs.”

Learn More in Zediker Books
Glen has authored a number of excellent books for hand-loaders and competitive shooters. Here are three of his most popular titles, including his latest book, Top Grade Ammo:

zediker book glen top grade ammo zediker book glen top grade ammo zediker book glen top grade ammo

All these titles are available from Midsouth Shooters Supply. Click each cover above to purchase from Midsouth.

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October 5th, 2019

Hybrid Bullets: How to Optimize Your Seating Depths

Berger Hybrid Bullet

Every year at SHOT Show in January, bullet-makers showcase their latest and greatest projectiles for hunters and paper-punchers. we plan to get the “inside scoop” on new bullet designs from Berger, Hornady, Lapua, Nosler and Sierra.

A while back, at SHOT Show 2012 we chatted with Berger Ballistician Bryan Litz about Berger’s popular line of Hybrid bullets. Berger now offers a wide range of Hybrids in multiple calibers and weights. In fact, for .30-Caliber shooters, Berger now offers many seven (7) Hybrid match bullets, with weights from 155 grains up to 230 grains. Two .338-caliber OTM Tactical Hybrids were introduced in 2012 (a 250-grainer and a 300-grainer).

Bryan tells us: “The hybrid design is Berger’s solution to the age old problem of precision vs. ease of use. This design is making life easier for handloaders as well as providing opportunities for commercial ammo loaders who need to offer a high performance round that also shoots precisely in many rifles with various chamber/throat configurations.”

For those not familiar with Hybrid bullets, the Hybrid design blends two common bullet nose shapes on the front section of the bullet (from the tip to the start of the bearing surface). Most of the curved section of the bullet has a Secant (VLD-style) ogive for low drag. This then blends in a Tangent-style ogive curve further back, where the bullet first contacts the rifling. The Tangent section makes seating depth less critical to accuracy, so the Hybrid bullet can shoot well through a range of seating depths, even though it has a very high Ballistic Coefficient (BC).

In the video we asked Bryan for recommended seating depths for 7mm and .30-Caliber Hybrid bullets. Bryan advises that, as a starting point, Hybrid bullets be seated .015″ (fifteen thousandths) off the lands in most barrels. Watch the video for more tips how to optimize your loads with Hybrid bullets.

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October 7th, 2018

Darrell Holland Upgrade for RCBS Bench Priming Tool

Priming Tool Holland Perfect RCBS bench mount primer

Gunsmith Darrell Holland sells a priming tool that upgrades the RCBS Auto Bench Priming Tool with key features — including primer seating depth control. If your hand starts to hurt after priming dozens of cases with a hand-held, squeeze-type priming tool, you may want to consider Holland’s invention, which he calls the “Perfect Primer Seater” (PPS).

Holland basically has modified the RCBS lever, adding a precise crush control and a means of measuring depth with a gauge. He claims this gives “an EXACT primer seating depth based on primer pocket depth and primer thickness”. With Holland’s PPS, primer seating depth is controlled with a rotating wheel that limits lever travel in precise gradations. You can buy the complete priming system for $215.00, or, if you already own the RCBS Auto Prime tool, you can purchase an adapter kit (with base, arm, adjuster, and gauge etc.) for $120.00. To order, visit Hollandguns.com. Click on “Reloading Equipment”, and look for the Perfect Primer Seater. Scroll down to the bottom of the page to add items to the shopping cart.

Priming Tool Holland Perfect RCBS bench mount primer

Priming Tool Holland Perfect RCBS bench mount primerUser Review by Tommy Todd
Sierra Bullets’ Chief Ballistician Tommy Todd acquired the Holland Perfect Primer Seater, and gave it a positive review. Todd writes: “This cartridge case priming system allows you to measure the primer pocket depth and adjust the seating tool to match the primer seating depth for a contact fit with a measured lot of primers to the cases you are working with. Mr. Darrell Holland has taken a standard RCBS automatic bench-mounted priming tool and modified it to a new level of precision. The modifications allow you to measure the primer pocket depth, primer height, and with the addition of an adjustable stop on the priming tool achieve precision primer seating, rather than how the primer ‘feels'[.]

If you are already utilizing the RCBS priming tool, Mr. Holland offers an adapter kit to upgrade your equipment. If you are looking for a new priming unit, I suggest giving this product a try. Increasing consistency when seating primers should result in smaller groups[.]”

Permalink Bullets, Brass, Ammo, Gear Review, Reloading 4 Comments »
July 6th, 2018

TECH Tip: Safe Loading Practices for Different Bullet Shapes

USAMU Reloading Bullet Safety

This article, from the USAMU Facebook Page, concerns reloading safety. In the relentless quest for more speed and flatter ballistics, some hand-loaders load way too hot, running charges that exceed safe pressure levels. Hint: If you need a mallet to open your bolt, chances are your load is too hot. Stay within safe margins — your equipment will last longer, and you won’t risk an injury caused by over-pressure. In this article, the USAMU explains that you need to account for bullet shape, diameter, and bearing surface when working up a load. Don’t assume that a load which is safe for one bullet will be safe for another even if both bullets are exactly the same weight.

USAMU Reloading tips Army Marksmanship

Today, we continue our handloading safety theme, focusing on not inadvertently exceeding the boundaries of known, safe data.

Bullet manufacturers’ loading manuals often display three, four, or more similar-weight bullets grouped together with one set of load recipes. The manufacturer has tested these bullets and developed safe data for that group. However, seeing data in this format can tempt loaders — especially new ones — to think that ALL bullets of a given weight and caliber can interchangeably use the same load data. Actually, not so much.

The researchers ensure their data is safe with the bullet yielding the highest pressure. Thus, all others in that group should produce equal or less pressure, and they are safe using this data.

However, bullet designs include many variables such as different bearing surface lengths, hardness, and even slight variations in diameter. In fact, diameters can occasionally range up to 0.001″ by design. Thus, choosing untested bullets of the same weight and caliber, and using them with data not developed for them can yield excess pressures.

This is only one of the countless reasons not to begin at or very near the highest pressure loads during load development. Always begin at the starting load and look for pressure signs as one increases powder charges.

Bullet Bearing Surface and Pressure
Bullet bearing surface length (BSL) is often overlooked when considering maximum safe powder charges and pressures. In Photo 1, note the differences in the bullets’ appearance. All three are 7 mm, and their maximum weight difference is just five grains. Yet, the traditional round nose, flat base design on the left appears to have much more BSL than the sleeker match bullets. All things being equal, based on appearance, the RN/FB bullet seems likely to reach maximum pressure with significantly less powder than the other two designs.

Photo 1: Three Near-Equal-Weight 7mm Bullets with Different Shapes
USAMU Bullet Ogive Comparison Safety Reloading

Due to time constraints, the writer used an approximate, direct measurement approach to assess the bullets’ different BSLs. While fairly repeatable, the results were far from ballistics engineer-grade. Still, they are adequate for this example.

Bullet 1 (L-R), the RN/FB, has a very slight taper and only reaches its full diameter (0.284 inch) very near the cannelure. This taper is often seen on similar bullets; it helps reduce pressures with good accuracy. The calculated BSL of Bullet 1 was ~0.324″. The BSL of Bullet 2, in the center, was ~0.430″, and Bullet 3’s was ~ 0.463″. Obviously, bullets can be visually deceiving as to BSL!

Some might be tempted to use a bullet ogive comparator (or two) to measure bullets’ true BSL for comparison’s sake. Unfortunately, comparators don’t typically measure maximum bullet diameter and this approach can be deluding.

Photo 2: The Perils of Measuring Bearing Surface Length with Comparators
USAMU Bullet Ogive Comparision Safety Reloading

In Photo 2, two 7mm comparators have been installed on a dial caliper in an attempt to measure BSL. Using this approach, the BSLs differed sharply from the original [measurements]. The comparator-measured Bullet 1 BSL was 0.694” vs. 0.324” (original), Bullet 2 was 0.601” (comparator) vs. 0.430” (original), and Bullet 3 (shown in Photo 2) was 0.602” (comparator) vs. 0.463” (original). [Editor’s comment — Note the very large difference for Bullet 1, masking the fact that the true full diameter on this bullet starts very far back. You can use comparators on calipers, but be aware that this method may give you deceptive reading — we’ve seen variances just by reversing the comparators on the calipers, because the comparators, typically, are not perfectly round, nor are they machined to precision tolerances.]

Thanks to the U.S. Army Marksmanship Unit for allowing the reprint of this article.

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November 1st, 2017

Long Range Load Development for F-Class

7mm F-Class long range load development Mark Walker Sierra Bullets

This article was written in 2014 for the Sierra Bullets Blog. It describes one method of load development that is commonly used. There are other methods that can work also. Some guys first isolate seating depth and then fine-tune velocity with charge weights. Other guys may aim for a known velocity node (speed range) and then optimize accuracy by adjusting seating depth. Still others look for smallest ES and tightest vertical to minimize 1000-yard vertical dispersion. There are many ways to skin a cat. Different rifles (and even different barrels) can demand different styles of load development.

In this instance the writer achieved desired results seating his bullets .007″ back from max “jam” length. For other applications (and other barrels) you may get the best, most consistent results seating off the rifling by .020″ or more. In disciplines with quick-fire such as PRS, it may be wise to develop loads that “jump” the bullet.

F-Class Long Range Load Development Methodology

by Mark Walker, Sierra Bullets Product Development Manager
Since I just put a new barrel on my F-class rifle… I figured it might be a good time to discuss load tuning for long range shooting. Getting the most accuracy out of your rifle is one of the most important aspects of load tuning. For long range shooting in particular, using a load that produces the least amount of vertical variation is vital. There are several steps to the process that I use, so I will go through the basics of each.

When I first get a new barrel installed, I like to determine what the loaded cartridge “jam” length is. I do this by taking an empty case (no powder or primer) that has been neck sized with the proper bushing (I like to shoot for 0.002 smaller than the loaded cartridge neck diameter) and seat a bullet long in it so that the throat of the rifle will move the bullet back into the case when I close the bolt. I close the bolt several times until the bullet stops moving back into the case at which point I use a comparator with my calipers and get a length measurement on the cartridge. This is what I consider to be the “jam length” for this barrel and chamber. I came up with 3.477″ as the “jam length” for this particular barrel. [Editor: In this instance, Mark is using “Jam length” to mean max seating depth he can achieve without bullet set-back.]

Next, I will fire-form some brass using a starting load of powder and bullets seated to “jam” while breaking in the barrel. My barrel break in process is not very technical; it’s mostly just to get the brass formed and the rifle sighted in. I do clean every 5 rounds or so just because I feel like I have to.

Once I have the brass formed, I use them to load for a “ladder test” to see what powder charge the rifle likes. With a ladder test, you take your starting load and load one round each with a slightly increasing amount of powder until you reach your max load for that cartridge. You then fire each round using the same aiming point to see where the bullets start to form a group. For this barrel and cartridge, I started at 53.3 grains of H4831SC powder and increased the load by 0.3 grains until I reached 55.7 grains. I always seat my bullets to “jam” when doing a ladder test. We will determine the final seating depth in another test later. It’s usually best to shoot this test at a minimum of 200 yards because at closer ranges the bullets will impact too close together making it hard to determine which load works best. I shot this test at 300 yards.

7mm F-Class long range load development Mark Walker Sierra Bullets

As you can see from the target, the lightest load #1 had the lowest velocity and impacted lowest on the target. Shots #2 and #3 were a little higher and in the same hole. Shots #4 thru #6 were slightly higher yet and all had the same elevation. Shots #7 and #8 were the highest on the target however pressure signs were starting to show. For some reason shot #9 went back into the group and the chronograph didn’t get a reading so I ignored that shot.

When picking a load, I am looking for the most shots at the same vertical location on the target. As you can see that would be shots #4 through #6 so I would pick a powder charge from those shots which would be 54.2 grains to 54.8 grains. As a side note, shots #2 and #3 are only 0.851 lower so I wouldn’t be afraid of using one of those loads either. I settled on 54.5 grains as the load I wanted to use. It’s right in the middle of the group so if the velocity goes up or down slightly, the bullet should still hit in the same place on the target.

Now that we’ve settled on a powder charge, I want to find the seating depth the rifle likes. I usually start at jam length and [shorten the COAL] in 0.003 increments until I get to 0.015 deeper than jam. [Editor: By this he means he is seating the BULLET deeper in the case, NOT deeper into the lands. He ended up at .007″ shorter than his hard jam length of 3.477″.]

I load 3 rounds at each depth using the 54.5 grain powder charge and shoot a group with each depth at 150 yards. As you can see from the target, the first two groups are not good at all. Next one looks good and is the smallest group on the target. The next three are not quite as small but the vertical location on the target is almost the same which indicates a sweet spot which will help keep the vertical stringing to a minimum on target. I went with 3.470″ which is right in the middle once again and should give some flexibility with the seating depth.

7mm F-Class long range load development Mark Walker Sierra Bullets

So after all of that, my load is 54.5 grains of H4831SC and a cartridge length of 3.470. I plan on loading up enough ammo to shoot five groups of five shots and see exactly how this load works on target as well as what the extreme velocity spreads are over several groups.

I sincerely hope some of this information helps you to get the best accuracy out of your rifle. I do not take credit for coming up with any of this, a whole lot of good shooters use this same method or a variant of it when working up their loads.

For more information about load development, please contact the Sierra Bullets technical support team at 1-800-223-8799 or by email at sierra [at] sierrabullets.com.

Disclaimer: Load data represented here may not be safe in your rifle. Always start low and work up, watching for pressure signs.

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October 26th, 2014

Berger Article on COAL and Cartridge Base-to-Ogive PART 2

Berger Bullets COAL length cartridgeEffects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 2
by Bryan Litz for Berger Bullets.
Part One of this series focused on the importance of COAL in terms of SAAMI standards, magazine lengths, seating depths, and pressure levels. Another measure of length for loaded ammunition is highly important to precision, namely Cartridge Base to Bullet Ogive Length (CBTO).

Figure 2. Chamber throat geometry showing the bullet jump to the rifling or lands.
chamber length loading berger bullets

Look at Figure 2. Suppose the bullet was seated out of the case to the point where the base of the bullet’s nose (ogive) just contacted the beginning of the riflings (the lands) when the bolt was closed. This bullet seating configuration is referred to as touching the lands, or touching the riflings and is a very important measurement to understand for precision hand-loading. Due to the complex dynamics of internal ballistics which happen in the blink of an eye, the distance a bullet moves out of the case before it engages the riflings is highly critical to precision potential. Therefore, in order to systematically optimize the precision of his handloads, it’s critically important that the precision hand-loader understands how to alter bullet seating depth in relation to the barrel rifling. Part of the required knowledge is understanding how to accurately and repeatably measure the Cartridge Base To Ogive (CBTO) dimension. This is explained in the FULL ARTICLE.

Bryan Litz offers an extended discussion on how to measure CBTO using different tools and methods, including the Hornady OAL gauge. You can read this discussion in the full article found on the Berger Bullets website. CLICK HERE to Read Full Article.

Why Not Use CBTO as a SAAMI Standard?
If CBTO is so important to rifle accuracy, you might ask, “Why is it not listed as the SAAMI spec standard in addition to COAL?” There is one primary reason why it is not listed in the standard. This is the lack of uniformity in bullet nose shapes and measuring devices used to determine CBTO.

Figure 4. Two different bullet shapes, seated to the same CBTO length, but different COAL. Note the shiny scratches on the bullets made by the comparator tool which indicates a point on the bullet ogive near where the ogive will engage the riflings.

chamber length loading berger bullets

Benefits of Having a Uniform CBTO
There is another aspect to knowing your CBTO when checking your COAL as it pertains to performance. With good bullets, tooling, and carefully-prepared cases you can easily achieve a CBTO that varies less than +/- .001″ but your COAL can vary as much as .025″ extreme spread (or more with other brands). This is not necessarily bad and it is much better than the other way around. If you have a CBTO dimension that varies but your COAL dimension is tight (within +/- .002″) then it is most likely that your bullet is bottoming out inside the seater cone on the bullet tip. This is very bad and is to be avoided. It is normal for bullets to have precisely the same nose shape and it is also normal for these same bullets to have nose lengths that can vary as much as .025″.

Summary of Cartridge Base To Ogive (CBTO) Discussion
Here are four important considerations regarding bullet seating depth as it relates to CBTO:

1. CBTO is a critical measurement to understand for handloaders because it’s directly related to precision potential, and you control it by simply setting bullet seating depth.

2. Tools and methods for measuring CBTO vary. Most of the measurement techniques have pitfalls (which may give rise to inconsistent results) that you should understand before starting out.

3. A CBTO that produces the best precision in your rifle may not produce the best precision in someone else’s rifle. Even if you have the same rifle, same bullets, same model of comparator gauges, etc. It’s possible that the gauges are not actually the same, and measurements from one don’t translate to the same dimension for another.

4. Once you find the CBTO that produces the best precision in your rifle, it’s important to allow minimal variation in that dimension when producing quality handloads. This is achieved by using quality bullets, tooling, and properly preparing case mouths and necks for consistent seating.

CLICK HERE to Read Full Article with More Info
Article sourced by EdLongrange. We welcome tips from readers.
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May 19th, 2013

Berger Article on Cartridge Overall Length and Base-to-Ogive

Berger Bullets COAL length cartridgeEffects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 1
by Bryan Litz for Berger Bullets.
Many shooters are not aware of the dramatic effects that bullet seating depth can have on the pressure and velocity generated by a rifle cartridge. Cartridge Overall Length (COAL) is also a variable that can be used to fine-tune accuracy. It’s also an important consideration for rifles that need to feed rounds through a magazine. In this article, we’ll explore the various effects of COAL, and what choices a shooter can make to maximize the effectiveness of their hand loads.

Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI)
Most loading manuals (including the Berger Manual), present loading data according to SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) standards. SAAMI provides max pressure, COAL and many other specifications for commercial cartridges so that rifle makers, ammo makers, and hand loaders can standardize their products so they all work together. As we’ll see later in this article, these SAAMI standards are in many cases outdated and can dramatically restrict the performance potential of a cartridge.

Bullet seating depth is an important variable in the accuracy equation. In many cases, the SAAMI specified COAL is shorter than what a hand loader wants to load their rounds to for accuracy purposes. In the case where a hand loader seats the bullets longer than SAAMI specified COAL, there are some internal ballistic effects that take place which are important to understand.

Effects of Seating Depth / COAL on Pressure and Velocity
The primary effect of loading a cartridge long is that it leaves more internal volume inside the cartridge. This extra internal volume has a well known effect; for a given powder charge, there will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you have to use more powder to achieve the same pressure and velocity when the bullet is seated out long. In fact, the extra powder you can add to a cartridge with the bullet seated long will allow you to achieve greater velocity at the same pressure than a cartridge with a bullet seated short.

Berger Bullets COAL length cartridge

Figure 1. When the bullet is seated farther out of the case, there is more volume available for powder. This enables the cartridge to generate higher muzzle velocity with the same pressure.

When you think about it, it makes good sense. After all, when you seat the bullet out longer and leave more internal case volume for powder, you’re effectively making the cartridge into a bigger cartridge by increasing the size of the combustion chamber. Figure 1 illustrates the extra volume that’s available for powder when the bullet is seated out long.

Before concluding that it’s a good idea to start seating your bullets longer than SAAMI spec length, there are a few things to consider.

Geometry of a Chamber Throat
The chamber in a rifle will have a certain throat length which will dictate how long a bullet can be loaded. The throat is the forward portion of the chamber that has no rifling. The portion of the bullet’s bearing surface that projects out of the case occupies the throat (see Figure 2).

Berger Bullets COAL length cartridge

The length of the throat determines how much of the bullet can stick out of the case. When a cartridge is chambered and the bullet encounters the beginning of the rifling, known as the lands, it’s met with hard resistance. This COAL marks the maximum length that a bullet can be seated. When a bullet is seated out to contact the lands, its initial forward motion during ignition is immediately resisted by an engraving force.

Seating a bullet against the lands causes pressures to be elevated noticeably higher than if the bullet were seated just a few thousandths of an inch off the lands.

A very common practice in precision reloading is to establish the COAL for a bullet that’s seated to touch the lands. This is a reference length that the hand loader works from when searching for the optimal seating depth for precision. Many times, the best seating depth is with the bullet touching or very near the lands. However, in some rifles, the best seating depth might be 0.100″ or more off the lands. This is simply a variable the hand loader uses to tune the precision of a rifle.

CLICK HERE to Read Full Article with More Info

Article sourced by EdLongrange. We welcome tips from readers.
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July 11th, 2012

TOOL TIP: Make Your Own Length-to-Lands Gauge

To achieve best accuracy with a rifle, you must control bullet seating depth very precisely, so all bullets end up in the same place relative to the entrance of the lands, every time. There may be multiple cartridge OALs which prove accurate. However, with each, you first need to determine a “zero” point — a reliable, and repeatable OAL where the bullet is “just touching” the lands.

There are tools, such as the Hornady (formerly Stoney Point) OAL Gauge, that will help you find a seating OAL just touching the lands. However, the tool requires that you use a special modified case for each cartridge you shoot. And, while we find that the Hornady OAL Gauge is repeatable, it does take some practice to get in right.

Make Your Own Length-to-Lands Gauge with a Dremel
Here’s an inexpensive alternative to the Hornady OAL tool — a slotted case. Forum member Andris Silins explains how to create a slotted case to measure length to the lands in your rifle:

“Here’s what I did to find length to lands for seating my bullets. I made four cuts into the neck of fire-formed brass. Then I pressed the bullet in lightly and chambered the entire gauge. As the cartridge chambers, the bullet slides back into the case to give you length to lands. It took less than five minutes to get it cut and working. A little light oil in the barrel just past the chamber helps ensure the bullet does not get stuck in the lands. It works great and is very accurate.

case OAL gauge home made

I made the cuts using a Dremel with a cut-off wheel. You can adjust tension two ways. First, you can make the cuts longer or shorter. Longer cuts = less tension. If you used only three cuts instead of four you would get more tension. The trick is to be gentle when you open and close the bolt. If you ram the bolt closed you may wedge the bullet into the lands. When you open the bolt it helps to keep a finger or two near by to guide the case out straight because the ejector wants to push it sideways.”

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