Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
The reason shooters work with tools and gauges to measure and control concentricity is simple: to make sure the bullet starts down the bore consistently in line with the bore. If the case isn’t properly concentric and the bullet isn’t properly aligned down the center of the bore, the bullet will enter the rifling inconsistently. While the bore might force the bullet to align itself with the bore (but normally it doesn’t), the bullet may be damaged or overstressed in the process – if it even it corrects itself in transit. These are issues we strive to remedy by handloading, to maintain the best standard possible for accurate ammunition.
The term “concentricity” is derived from “concentric circle”. In simple terms it’s the issue of having the outside of the cartridge in a concentric circle around the center. That goes from case head and center of the flash hole, to the tip of the bullet.
Factors Affecting Concentricity
The point of using this term is to identify a series of issues that affect accurate ammunition. Ideally this would work best with a straight-walled case; but since most rifle cartridge cases are tapered, it equates to the smallest cross section that can be measured point by point to verify the concentric circle around the center. For the examples below, I’m working with .308 Winchester ammo.
Figure 1: The cartridge.
Figure 2: Centerline axis of the case, extending from flash hole to case mouth.
The case walls have to be in perfect alignment with the center, or axis, of that case, even if it’s measured at a thousandth of an inch per segment (in a tapered case).
Figure 3: Case body in alignment with its axis, or centerline, even in a tapered case.
The case neck must also be in alignment with its axis. By not doing so you can have erratic bullet entry into the bore. The case neck wall itself should be as uniform as possible in alignment and in thickness (see the M80 7.62x51mm NATO cartridge in Figure 5) and brass can change its alignment and shape. It’s why we expand the case neck or while some folks ream the inside of the neck and then turn the outside for consistent thickness, which affects the tension on the bullet when seated.
Figure 4: Neck in alignment with center of the case axis.
Figure 5: Variations in case neck wall thickness, especially on some military brass, can cause an offset of the bullet in its alignment. This is an M80 ball round. Note the distinct difference of the neck walls.
Having a ball micrometer on hand helps, especially with military brass like 7.62x51mm in a semi-auto rifle, where there are limits as to how thin you want the neck walls to be. In the case of 7.62 ball brass you want to keep the wall to .0145″.
Figure 6: A ball micrometer like this RCBS tool (#100-010-268) can measure case neck thickness.
Turning the outside of the neck wall is important with .308 military cases regardless of whether you expand or ream the neck walls. There are several outside neck turning tools from Forster, Hornady, Sinclair, and others. I’ve been using classic Forster case trimming (#100-203-301) and neck turning (#749-012-890) tools for 40 years.
Bullet Run-Out
The cartridge, after being loaded, still needs to be in alignment with the center of the case axis. Figure 7 shows a bad example of this, a round of M80 ball. A tilted bullet is measured for what’s known as bullet “run-out”.
Figure 7: An M80 round with the bullet tilted and not aligned with the axis. This will be a flyer!
Run-out can be affected by several things: (1) improperly indexing your case while sizing, which includes not using the proper shell holder, especially while using a normal expander ball on the sizing die (it also can stretch the brass). (2) The head of a turret press can flex; and (3) improper or sloppy bullet seating. This is also relevant when it comes to using a progressive press when trying to load accuracy ammo.
Mid Tompkins came up with a simple solution for better bullet seating years ago. Seat your bullet half way into the case, back off the seater die and rotate the case 180 degrees before you finish seating the bullet. It cuts down on run-out problems, especially with military brass. You also want to gently ream the inside of the neck mouth to keep from having any brass mar the surface of the bullet jacket and make proper seating easier. A tilted bullet often means a flyer.
Figure 8: Proper alignment from the center of the case head to the tip of the bullet.
(NOTE: This links to a Web Archive version of the original Sinclair Int’l article.)
*Actually some folks would say that if we are talking about things being off-center or out-of-round, we are actually talking about “eccentricity”. But the tools we use are called “Concentricity Gauges” and Concentricity is the term most commonly used when discussing this subject.
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Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
The reason shooters work with tools and gauges to measure and control concentricity is simple: to make sure the bullet starts down the bore consistently in line with the bore. If the case isn’t properly concentric and the bullet isn’t properly aligned down the center of the bore, the bullet will enter the rifling inconsistently. While the bore might force the bullet to align itself with the bore (but normally it doesn’t), the bullet may be damaged or overstressed in the process – if it even it corrects itself in transit. These are issues we strive to remedy by handloading, to maintain the best standard possible for accurate ammunition.
The term “concentricity” is derived from “concentric circle”. In simple terms it’s the issue of having the outside of the cartridge in a concentric circle around the center. That goes from case head and center of the flash hole, to the tip of the bullet.
Factors Affecting Concentricity
The point of using this term is to identify a series of issues that affect accurate ammunition. Ideally this would work best with a straight-walled case; but since most rifle cartridge cases are tapered, it equates to the smallest cross section that can be measured point by point to verify the concentric circle around the center. For the examples below, I’m working with .308 Winchester ammo.
Figure 1: The cartridge.
Figure 2: Centerline axis of the case, extending from flash hole to case mouth.
The case walls have to be in perfect alignment with the center, or axis, of that case, even if it’s measured at a thousandth of an inch per segment (in a tapered case).
Figure 3: Case body in alignment with its axis, or centerline, even in a tapered case.
The case neck must also be in alignment with its axis. By not doing so you can have erratic bullet entry into the bore. The case neck wall itself should be as uniform as possible in alignment and in thickness (see the M80 7.62x51mm NATO cartridge in Figure 5) and brass can change its alignment and shape. It’s why we expand the case neck or while some folks ream the inside of the neck and then turn the outside for consistent thickness, which affects the tension on the bullet when seated.
Figure 4: Neck in alignment with center of the case axis.
Figure 5: Variations in case neck wall thickness, especially on some military brass, can cause an offset of the bullet in its alignment. This is an M80 ball round. Note the distinct difference of the neck walls.
Having a ball micrometer on hand helps, especially with military brass like 7.62x51mm in a semi-auto rifle, where there are limits as to how thin you want the neck walls to be. In the case of 7.62 ball brass you want to keep the wall to .0145″.
Figure 6: A ball micrometer like this RCBS tool (#100-010-268) can measure case neck thickness.
Turning the outside of the neck wall is important with .308 military cases regardless of whether you expand or ream the neck walls. There are several outside neck turning tools from Forster, Hornady, Sinclair, and others. I’ve been using classic Forster case trimming (#100-203-301) and neck turning (#749-012-890) tools for 40 years.
Bullet Run-Out
The cartridge, after being loaded, still needs to be in alignment with the center of the case axis. Figure 7 shows a bad example of this, a round of M80 ball. A tilted bullet is measured for what’s known as bullet “run-out”.
Figure 7: An M80 round with the bullet tilted and not aligned with the axis. This will be a flyer!
Run-out can be affected by several things: (1) improperly indexing your case while sizing, which includes not using the proper shell holder, especially while using a normal expander ball on the sizing die (it also can stretch the brass). (2) The head of a turret press can flex; and (3) improper or sloppy bullet seating. This is also relevant when it comes to using a progressive press when trying to load accuracy ammo.
Mid Tompkins came up with a simple solution for better bullet seating years ago. Seat your bullet half way into the case, back off the seater die and rotate the case 180 degrees before you finish seating the bullet. It cuts down on run-out problems, especially with military brass. You also want to gently ream the inside of the neck mouth to keep from having any brass mar the surface of the bullet jacket and make proper seating easier. A tilted bullet often means a flyer.
Figure 8: Proper alignment from the center of the case head to the tip of the bullet.
(NOTE: This links to a Web Archive version of the original Sinclair Int’l article.)
*Actually some folks would say that if we are talking about things being off-center or out-of-round, we are actually talking about “eccentricity”. But the tools we use are called “Concentricity Gauges” and Concentricity is the term most commonly used when discussing this subject.
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Forum member F-Class John is an avid F-Class competitor and expert handloader. John reviews reloading hardware and shooting-related products for his popular F-Class John YouTube Channel, which now boasts 500+ videos. John also does important product testing for AccurateShooter.com. Through his YouTube channel, John has reviewed many of the latest and greatest reloading tools and accessories. For today’s Video Showcase, we selected six F-Class John product reviews. Products tested include front rests, borescopes, precision triggers, ammo caddies, steel rimfire targets, and a concentricity checker.
If you like these informative videos, consider joining F-Class John’s Patreon Channel for live video meetings, more in-depth videos, and detailed explanations. Join Patreon via Patreon.com/fclassjohn for full length videos, live chats, and more.
SEB NEO-X and Rodzilla Raptor Front Rests
This video covers two outstanding front joystick rests, the SEB Neo-X and the Rodzilla Raptor. Both of these rests work great for both benchrest and F-Class shooters, centerfire and rimfire. Build quality is outstanding for both rests. Tester F-Class John observes: “Both are great units and user preference will really dictate which to get. I own both and find they give me consistent target acquisition.” To learn more about these two excellent front rests, visit TheRodzilla.com and/or SEB Rests USA.
Testing Flavio Fare Triggers
The Flavio Fare triggers are some of the best on the market. These are offered for various action types including Remington clones and custom actions. CLICK HERE for a discussion of these triggers on our Forum. The Flavio Fare Veloce Hunting Trigger (with safety) adjusts from 5 to 25 ounces pull weight and retails for $439.95. The Flavio Fare Whisper 2.1 BenchRest Trigger (no safety) adjusts from 0.7 to 2.8 ounces, and costs $419.95. Reviewer F-Class John says these Flavio Fare triggers are “smooth, crisp, with a wide range of trigger pull weights … I love these things.”
Steel Targets for Rimfire Competition — Options Reviewed
NRL-22 and PRS Rimfire matches are growing in popularity. These types of competition are fun because reactive targets are used at the matches. Such targets provide “instant gratification” for a good shot — you hear a “ping” and may see the target swing or rotate. This video reviews a large variety of rimfire steel targets from D-M Targets. F-Class John notes: “These D-M Targets rimfire metal targets set-up quickly and easily. These targets are made from good steel and produce a good sound when hit.” John also observed that these DM steel rimfire targets don’t hang up when hit.
Teslong BoreScope Comparison — NTG500H and NTG450H Models
All serious rifle shooters should have a good digital borescope that allows you to view the inside of your rifle barrels. That helps you diagnose fouling/wear issues and evaluate the effectiveness of your cleaning procedures. Teslong makes some of the most popular electronic borescope systems. There are versions that can connect to your smartphone, iPad, or mobile device. We like the Teslong units that have their own dedicated hard-case display unit. This ensures you don’t have to fiddle with smartphone software updates or security conflicts. In this video, F-Class John reviews two different Teslong Borescope systems: model NTG500H and model NTG450H. Both these units have their own control cases with glass display screens. John notes: “Both units are priced right, have great screens, and are easy to use.”
Ammunition Caddies for F-Class and Benchrest Competition
If you shoot at a quick pace during benchrest, varmint, or F-Class competition, you can definitely benefit by having a well-designed ammo caddie that puts your round within easy reach. This video reviews loaded ammo holders produced by Accurate Forum member BGInvestor using a 3-D printer. The video showcases two different versions, one dark blue for benchrest, and a second, larger black unit for F-Class which is shown above. This video review shows different ways to mount these ammo holders, and discusses the multiple block sizes which are offered. F-Class John says you’ll want to pick a caddie that suits your shooting style and particular discipline.
Concentricity Checking with Accuracy One Gauge
Every serious hand-loader needs a quality concentricity gauge. The Accuracy One Concentricity Gauge boasts a smart design that delivers precise, repeatable results. We like the unit’s easy adjustability and its ability to work in a variety of configurations. The Accuracy One Gauge measures internal and external neck runout of cartridge cases as well as seated bullet runout. It can also measure the runout of the ogive, bearing surface, and boat-tail of individual bullets. And it can even measure your primer pocket runout. Reviewer F-Class John notes: “I think this is the best concentricity tool on the market. Such a tool is a necessity for new loaders or those who are always setting up new dies.”
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Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
The reason shooters work with tools and gauges to measure and control concentricity is simple: to make sure the bullet starts down the bore consistently in line with the bore. If the case isn’t properly concentric and the bullet isn’t properly aligned down the center of the bore, the bullet will enter the rifling inconsistently. While the bore might force the bullet to align itself with the bore (but normally it doesn’t), the bullet may be damaged or overstressed in the process – if it even it corrects itself in transit. These are issues we strive to remedy by handloading, to maintain the best standard possible for accurate ammunition.
The term “concentricity” is derived from “concentric circle”. In simple terms it’s the issue of having the outside of the cartridge in a concentric circle around the center. That goes from case head and center of the flash hole, to the tip of the bullet.
Factors Affecting Concentricity
The point of using this term is to identify a series of issues that affect accurate ammunition. Ideally this would work best with a straight-walled case; but since most rifle cartridge cases are tapered, it equates to the smallest cross section that can be measured point by point to verify the concentric circle around the center. For the examples below, I’m working with .308 Winchester ammo.
Figure 1: The cartridge.
Figure 2: Centerline axis of the case, extending from flash hole to case mouth.
The case walls have to be in perfect alignment with the center, or axis, of that case, even if it’s measured at a thousandth of an inch per segment (in a tapered case).
Figure 3: Case body in alignment with its axis, or centerline, even in a tapered case.
The case neck must also be in alignment with its axis. By not doing so you can have erratic bullet entry into the bore. The case neck wall itself should be as uniform as possible in alignment and in thickness (see the M80 7.62x51mm NATO cartridge in Figure 5) and brass can change its alignment and shape. It’s why we expand the case neck or while some folks ream the inside of the neck and then turn the outside for consistent thickness, which affects the tension on the bullet when seated.
Figure 4: Neck in alignment with center of the case axis.
Figure 5: Variations in case neck wall thickness, especially on some military brass, can cause an offset of the bullet in its alignment. This is an M80 ball round. Note the distinct difference of the neck walls.
Having a ball micrometer on hand helps, especially with military brass like 7.62x51mm in a semi-auto rifle, where there are limits as to how thin you want the neck walls to be. In the case of 7.62 ball brass you want to keep the wall to .0145″.
Figure 6: A ball micrometer like this RCBS tool (#100-010-268) can measure case neck thickness.
Turning the outside of the neck wall is important with .308 military cases regardless of whether you expand or ream the neck walls. There are several outside neck turning tools from Forster, Hornady, Sinclair, and others. I’ve been using classic Forster case trimming (#100-203-301) and neck turning (#749-012-890) tools for 40 years.
Bullet Run-Out
The cartridge, after being loaded, still needs to be in alignment with the center of the case axis. Figure 7 shows a bad example of this, a round of M80 ball. A tilted bullet is measured for what’s known as bullet “run-out”.
Figure 7: An M80 round with the bullet tilted and not aligned with the axis. This will be a flyer!
Run-out can be affected by several things: (1) improperly indexing your case while sizing, which includes not using the proper shell holder, especially while using a normal expander ball on the sizing die (it also can stretch the brass). (2) The head of a turret press can flex; and (3) improper or sloppy bullet seating. This is also relevant when it comes to using a progressive press when trying to load accuracy ammo.
Mid Tompkins came up with a simple solution for better bullet seating years ago. Seat your bullet half way into the case, back off the seater die and rotate the case 180 degrees before you finish seating the bullet. It cuts down on run-out problems, especially with military brass. You also want to gently ream the inside of the neck mouth to keep from having any brass mar the surface of the bullet jacket and make proper seating easier. A tilted bullet often means a flyer.
Figure 8: Proper alignment from the center of the case head to the tip of the bullet.
(NOTE: This links to a Web Archive of the original Sinclair Int’l article.)
*Actually some folks would say that if we are talking about things being off-center or out-of-round, we are actually talking about “eccentricity”. But the tools we use are called “Concentricity Gauges” and Concentricity is the term most commonly used when discussing this subject.
Story Tip from EdLongrange. We welcome reader submissions.
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This image is from multi-time Nat’l Long Range Champion Nancy Tompkins, author of Prone and Long Range Rifle Shooting. Nancy loves to photograph the Aurora Borealis.
As a Christmas present for our readers, today we showcase eight very informative videos from AccurateShooter Forum member F-Class John. A talented F-Class competitor with a smart, technically-focused mind, John has created a series of videos about reloading and precision loading tools, along with rifle and shooting accessories. Many of John’s product reviews are the most thorough and detailed you’ll find in video format. You’ll find over 120 informative videos on F-Class John’s popular YouTube Channel.
21st Century Hydro Press and Arbor Press — Product Review
Many of the world’s top benchrest, long-range, and F-Class shooters prefer to seat their bullets using arbor-type presses with inline dies. This allows smooth, repeatable bullet-seating with very low run-out. One of the very best arbor-type seating presses ever created is the 21st Century Hydro Press. This offers plenty of leverage driving a precision ram. The Hydro Press also features a hydraulic line to drive a precision seating force gauge. Along with the Hydro Press, John tests 21st Century’s standard arbor press.
Cartridge Case Separation — Tell-Tale Warning Signs
If you reload and haven’t experienced a case separation yet then you are fortunate. It’s a fact of life in the shooting world. A bad case separation can have very unfortunate consequences. Therefore you need to watch for warning signs on your cartridge brass, so you stay safe. The video above shows what to look for — and how to recognize signs of incipient separation. One important factor leading to case head separation is improper head-spacing causing growth. To learn more about case head separation watch F-Class John’s follow-up video Case Head Separation Causes, identification and prevention.
Accuracy One Concentricity Gauge — Product review
Every person who makes precision hand-loads should have a quality concentricity gauge to measure run-out of case-necks and loaded rounds. Here John tests one of the best such tools on the market, the Accuracy One Concentricity Gauge. This measures the internal and external neck runout of cartridge cases as well as seated bullet runout. It can also measure the runout of the ogive, bearing surface, and boat-tail of individual bullets and can even measure primer pocket runout. John notes: “I think most precision shooters should have one of these to make sure their ammo is within their specs they’re happy with.”
How to Use a Barrel Tuner to Improve Accuracy and Repeatability
In this video, John works with a barrel tuner created by Erik Cortina, a member of Team Lapua/Brux/Borden. A tuner can be useful in modulating barrel vibrations and that can translate to smaller groups on target. Sometimes the positive effects are quite noticeable. Tuners have been popular with short-range benchresters for many years and now they are becoming more common on top F-Class and Long Range rifles.
John says: “I’ve been using Erik’s E.C. Tuner for a while now and I really like what it’s done to help as my final step in load development. Just remember, a tuner is a tool, not a magician. You still need good load development practices, good brass prep, and solid skills but the tuner does help make great loads even better.”
Teslong Rigid 26″ Borescope with 4.5″ Monitor — Product Review
There are a variety of affordable Teslong digital borescopes for inspecting your barrels and diagnosing issues. All Teslongs deliver impressively sharp images/video. Some units plug into a laptop or tablet, while others work via a dongle to communicate wirelessly. Here John tests a 26″ rigid model borescope that comes complete with its own 4.5″ viewing screen. Priced at $129.99 on Amazon, this system is completely self-contained — you don’t need a laptop or smartphone. You don’t have to worry about connections and there are no Apps to install or configure. John says: “Teslong now offers a 26″ rigid rod model with a 4.5″ monitor. This allows you to use the unit without the need for any mobile device or computer.”
Dillon 550 vs. Dillon 750 for Precision Reloading — Pros and Cons
Progressive presses are not just for bulk reloading these days. Many top shooters, including 5-time National Long Range Champion John Whidden, use Dillon progressive presses to complete many cartridge loading operations more efficiently. Even in the F-Class world, Top Guns such as Erik Cortina have found ways to use Dillon progressives for bullet pointing, case prep and other repetitious tasks, even if a precision arbor press is used for final bullet seating. In this video, F-Class John compares two Dillon options: “If you’re deciding between a Dillon 550 or 750/650 reloading press for precision reloading, here are some pros and cons of each. Both are capable of producing high quality ammunition but each has their own quirks so knowing your capabilities and loading style is important when choosing one over the other.
AutoTrickler V3 — General Set-Up and Operational Advice
In this video, John offers some general advice for setting-up the AutoTrickler system. He notes that you want to set the initial drop weight (from the powder measure) in an optimal range: “When you set the original drop you need it to be about 1 to 1.5 grains below. Some people set it too close to the final weight they want and it actually doesn’t let the trickler unit work as efficiently, consistently and accurately as it will if you start 1 to 1.5 grains low.” John also explains how to hook up the cords and how to position the trickler unit. John places his AutoTrickler on a 30-lb piece of granite, with a thin polymer “anti-static” pad on top. John also uses a line conditioner and grounding wire to provide the best electrical flow to the scale and trickler. John also shows how the angle of the trickler unit can be adjusted. If you own an AutoTrickler or plan to purchase one, we definitely recommend you watch this entire video.
ShotMarker Power-User Tip — How to Test Unit without Shooting
The ShotMarker is an advanced system that plots shot location using electronic sensors mounted on a frame. ShotMarker arrays are now used in many competitions because they are reliable, precise, and much more affordable than competing systems. Invented by Canadian Adam MacDonald, the ShotMarker plots bullet entry on target using sensors activated by the bullet’s soundwaves. Using 8 high precision MEMS microphones placed in the corners of your frame, ShotMarker precisely measures the point of impact and down-range velocity of each shot, so that you can analyze your groups and shoot for score in competition. In this video, John shows how you can quickly and easily test your ShotMarker before deploying it at the range: “Here’s a quick and simple way to ensure your system is working 100% before taking a shot on it.”
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Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
The reason shooters work with tools and gauges to measure and control concentricity is simple: to make sure the bullet starts down the bore consistently in line with the bore. If the case isn’t properly concentric and the bullet isn’t properly aligned down the center of the bore, the bullet will enter the rifling inconsistently. While the bore might force the bullet to align itself with the bore (but normally it doesn’t), the bullet may be damaged or overstressed in the process – if it even it corrects itself in transit. These are issues we strive to remedy by handloading, to maintain the best standard possible for accurate ammunition.
The term “concentricity” is derived from “concentric circle”. In simple terms it’s the issue of having the outside of the cartridge in a concentric circle around the center. That goes from case head and center of the flash hole, to the tip of the bullet.
Factors Affecting Concentricity
The point of using this term is to identify a series of issues that affect accurate ammunition. Ideally this would work best with a straight-walled case; but since most rifle cartridge cases are tapered, it equates to the smallest cross section that can be measured point by point to verify the concentric circle around the center. For the examples below, I’m working with .308 Winchester ammo.
Figure 1: The cartridge.
Figure 2: Centerline axis of the case, extending from flash hole to case mouth.
The case walls have to be in perfect alignment with the center, or axis, of that case, even if it’s measured at a thousandth of an inch per segment (in a tapered case).
Figure 3: Case body in alignment with its axis, or centerline, even in a tapered case.
The case neck must also be in alignment with its axis. By not doing so you can have erratic bullet entry into the bore. The case neck wall itself should be as uniform as possible in alignment and in thickness (see the M80 7.62x51mm NATO cartridge in Figure 5) and brass can change its alignment and shape. It’s why we expand the case neck or while some folks ream the inside of the neck and then turn the outside for consistent thickness, which affects the tension on the bullet when seated.
Figure 4: Neck in alignment with center of the case axis.
Figure 5: Variations in case neck wall thickness, especially on some military brass, can cause an offset of the bullet in its alignment. This is an M80 ball round. Note the distinct difference of the neck walls.
Having a ball micrometer on hand helps, especially with military brass like 7.62x51mm in a semi-auto rifle, where there are limits as to how thin you want the neck walls to be. In the case of 7.62 ball brass you want to keep the wall to .0145″.
Figure 6: A ball micrometer like this RCBS tool (#100-010-268) can measure case neck thickness.
Turning the outside of the neck wall is important with .308 military cases regardless of whether you expand or ream the neck walls. There are several outside neck turning tools from Forster, Hornady, Sinclair, and others. I’ve been using classic Forster case trimming (#100-203-301) and neck turning (#749-012-890) tools for 40 years.
Bullet Run-Out
The cartridge, after being loaded, still needs to be in alignment with the center of the case axis. Figure 7 shows a bad example of this, a round of M80 ball. A tilted bullet is measured for what’s known as bullet “run-out”.
Figure 7: An M80 round with the bullet tilted and not aligned with the axis. This will be a flyer!
Run-out can be affected by several things: (1) improperly indexing your case while sizing, which includes not using the proper shell holder, especially while using a normal expander ball on the sizing die (it also can stretch the brass). (2) The head of a turret press can flex; and (3) improper or sloppy bullet seating. This is also relevant when it comes to using a progressive press when trying to load accuracy ammo.
Mid Tompkins came up with a simple solution for better bullet seating years ago. Seat your bullet half way into the case, back off the seater die and rotate the case 180 degrees before you finish seating the bullet. It cuts down on run-out problems, especially with military brass. You also want to gently ream the inside of the neck mouth to keep from having any brass mar the surface of the bullet jacket and make proper seating easier. A tilted bullet often means a flyer.
Figure 8: Proper alignment from the center of the case head to the tip of the bullet.
(NOTE: This links to a Web Archive version of older Sinclair Int’l article.)
*Actually some folks would say that if we are talking about things being off-center or out-of-round, we are actually talking about “eccentricity”. But the tools we use are called “Concentricity Gauges” and Concentricity is the term most commonly used when discussing this subject.
Story Tip from EdLongrange. We welcome reader submissions.
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21st Century Shooting crafts some of the best precision handloading tools you can buy. This company’s neck-turning tools, priming tools, funnels, flash-hole tools, and other specialty tools are truly excellent pieces of kit. The 21st Century neck-turner, fitted in the company’s innovative neck-turning lathe, is an outstanding system for turning case-necks. Now holiday shoppers can save money on 21st Century’s entire product line. 21st Century is offering 10% off all products ordered through its website, www.21stCenturyShooting.com.
To get 10% off your online order, simply use the Discount Code 1210holiday25 during check-out, placing “1210holiday25″ in the box marked “REDEEM CODE”. With the money you save you can buy more cool tools, or set aside your savings for bullets, brass, and powder.
Discount Tip from EdLongrange. We welcome reader submissions.
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Talented tool-maker Curt Knitt has designed a better mousetrap — a new Concentricity Gauge that makes it easier than ever to get fast, repeatable results when measuring case and bullet run-out (aka “eccentricity”). The breakthrough design feature is the large-diameter wheel which spins the case. With most other concentricity gauges you must rotate the case with your finger(s). Anyone who has tried this knows that it is difficult to get a full, 360° rotation of the case without disturbing the indicator. Typically you can get two-thirds of a rotation or so, but then you have to reposition your finger to complete the rotation. Moving your finger often causes the case to jiggle or move slightly, and more often than not, the dial indicator jumps a bit, interrupting your measurement. Been there, done that.
Drive Wheel Smoothly Spins Cases for Fast, Error-Free Readouts
With the new Accuracy One Concentricity Gauge from CTK Precision, the rubber-rimmed drive wheel has a much larger diameter than any cartridge case (7:1 diameter ratio on magnums). So, when you rotate the drive wheel just a half-turn or so (using knurled knob on the wheel axis), you can easily and smoothly turn the cartridge three (or more) full rotations. The drive wheel maintains a constant, even load on the case, so the case doesn’t wobble and the dial indicator gives a continuous, un-interrupted read-out. What’s more, clever cartridge support design geometry pulls the case back against the rim stop as you engage the drive wheel. This holds the case in position laterally during measurement. Morever, this allows very fast one-handed operation. You don’t have to hold the case down with your fingers while maintaining side force against the case rim stop.
Watch Video Showing Concentricity Gauge Used with Small and Large Cartridges
The Accuracy One Concentricity Gauge works with the full range of cartridges — everything from .22LR to .50 BMG. Adjusting the tool for different-length cases is incredibly easy, because the roller blocks (case supports) are held in place by magnets. You just slide the blocks to the desired position — no tools needed! The indicator stand is also held by magnets so it can slide to any position you want along the case body or bullet. And, the indicator can be moved to the front rail and rotated 90°. This way you can measure on the inside of the case neck.
Does this new design really work? Absolutely — it works brilliantly and it’s FAST. Watch the video and see for yourself. We could do two-rotation (720°) measurements on cases in a third the time it takes to do a one-rotation gauging operation with other tools. And the actual measuring operation can be done one-handed, leaving your free hand to pic up the next case (or bullet) to be measured. And yes, this tool can also measure bullet concentricity — measured from tip, ogive, bearing surface, and/or boatail.
1. Directional Drive Wheel pushes the cartridge or bullet into the stop for accurate, repeatable readings with equal pressure. The replaceable rubber drive ring will not harm cartridges or bullets.
2. Two-position bullet and cartridge stop.
3. Precision ball bearings provide friction-free movement.
4. Heavy steel base with E-coat finish and bolt-on rubber feet.
5. Indicator stand and roller blocks ride in machined slots and are held in place by N42 Neodymium magnets. This allows rapid, smooth, tool-free adjustments.
6. Indicator stand can be place in front OR rear machined slots. This allows for both internal and external measurements.
7. Fine-Adjustment Horizontal Indicator Stand allows very precise indicator angle/load adjustments.
8. Indicator Stand will accept horizontal indicators that are .350″ wide or narrower, and are 1.75″ to 2.25″ from the indicator contact point to the center of the main body.
9. Adjustable mechanical arm stop holds the arm up for one-handed operation.
10. Precision Drive Wheel has a 13:1 ratio for .22 rimfire, 7:1 for magnums, and 3.7:1 for 50BMG.
11. Concentricity Gauge accepts cartridges from .22LR rimfire to .50 BMG.
The Accuracy One Concentricity Gauge is available from BulletTipping.com. Price for the unit, complete with quality horizontal indicator, is $325.00. Price, without indicator, is $280.00. The initial run of Concentricity Gauges is now in final production. Gauge sets should hit the market in 4 to 6 weeks. To place an advance order, fill out the PDF Order Form, or call (814) 684-5322. To learn more about setting up and using this new tool, read the Concentricity Gauge Instructions, and watch the video above.
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UltimateReloader.com created an informative video that shows how to use the new Hornady Lock-N-Load Concentricity Gauge and Ammo Straightener. This tool can measure run-out on both the bullet and on the case-necks. Run-out is deviation from the cartridge centerline axis. Too much run-out, i.e. poor concentricity, can reduce accuracy, although when you seat bullets into the lands, a certain amount of bullet self-straightening can take place.
Hornady Tool Supports Cartridge on Both Ends
The new Hornady Concentricity Tool supports the case at two ends. As a result, the Hornady Tool will tend to yield lower run-out figures than a tool such as the Sinclair concentricity checker which supports the cartridge on the case body alone, giving the bullet unrestricted movement as the case body is rotated. As UltimateReloader explains: “Each measurement tool measures run-out differently, so you’ll need to factor that into your goals for your own match ammunition.”
Bullet ‘Straightening’ with Hornady Concentricity Tool
The Hornady Tool can be used to push seated bullets to one side or the other, reducing measured run-out. The Hornady tool has a threaded pusher that side-loads the bullet. As you screw the pusher inwards in you can see the run-out on the dial indicator decrease. That straightening process is shown in the Hornady-produced video below, at the 25-second mark. In Sinclair Intl’s Reloading Press blog, Pete Petros reports: “It can take a little bit of trial and error to get this just right, but it does work.”
Is Bullet Straightening Really That Effective?
This bullet straightening procedure, whether done with the Hornady tool or other device, is a somewhat controversial technique. Some folks say that straightening bullets simply transfers run-out back down to the case neck. Petros notes: “One concern that comes up is what are you doing to the neck of the case in terms of neck tension.”
On the other hand, many shooters claim their ammo shoots better after they straightened rounds which initially showed excessive run-out. One Hornady Concentricity Tool user writes: “The straightening feature on the Hornady tool makes bullet/case concentricity easy to correct and after using this tool, I wouldn’t be without one. Variations on [my] cast bullets have gone .020″ and when straightened, I can get down to below .001″. It takes a bit of practice, but it’s possible to make every round straight. At the 100-yard range yesterday using my straightened rounds … five-shot groups averaged .500. Before I would always have flyers and now I can see why this time I didn’t have any flyers. Straight rounds produce more consistent groups!”. Read more.
Bullet straightening with the Hornady Tool or other devices can certainly make a difference in run-out that shows up on the dial. Whether that improvement in perceived concentricity actually produces better accuracy remains an open question. Using high-quality dies with good bullets, seated in good, straight brass, you should be able to load ammo with very low run-out from the get-go. It may be better to try to achieve low run-out during your normal loading process rather than rely on the “band-aid” of bullet straightening as a last resort. On the other hand, if you are starting with factory-loaded ammo, re-aligning bullets in the case-necks may be a useful exercise. We invite our readers to comment on their experiences with bullet straightening. Has the straightening process worked for you?
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Grafs.com is having a big sale on certain Hornady reloading products. The Lock N Load Auto Charge Scale/Powder Dispenser is now just $199.99, marked down from $224.99. Reports on this unit have been generally positive. This sale makes the Hornady scale/dispenser much less expensive than an RCBS Chargemaster, which typically sells for about $330.00.
Next, the price of the Hornady Lock N Load Ultrasonic Cleaning Machine has been knocked down to $84.99 from $99.99. That makes the machine cheaper than “no-name” alternatives sold on eBay. This is similar to the machine we used for our original ultrasonic cleaning tests. It should do the job, unless you have large quantities of brass, in which case we recommend the larger Hornady Magnum Sonic Cleaning Machine, which has twin transducers and a larger immersion bay.
Grafs.com has also slashed the price of the Hornady Concentricity Gauge from $94.99 to $79.99. This tool can measure bullet run-out, and it has the capacity to straighten bullet alignment in the neck. Be aware, however, that because this tool supports a cartridge at both ends (like holding the two ends of a jump-rope), you will typically get a different run-out reading than with a traditional tool, such as the Sinclair Concentricity Gauge, which supports the case body only (without touching the bullet tip). Both tool designs give meaningful results, but the read-outs will not normally be the same.
Hornady Reloading Handbook $10.00 with Bullet Purchase
In addition to the tool sales, Grafs.com is now offering the lastest Hornady Reloading Handbook for just $10.00 if you purchase five (5) boxes of in-stock Hornady Bullets. If you could use the book, we recommend Hornady’s V-Max bullets for varmint hunters, and the new BTHP match bullets for target shooters. The new BTHP match bullets feature AMP (Advanced Manufacturing Process) jackets for greater dimensional uniformity.
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In our feature article on Case Neck Tools we explained the importance of case neck uniformity and reviewed the best tools for measuring case neck thickness. But having uniform case neck walls is only part of the accuracy equation. You also want your cases to exhibit minimal run-out, as measured by a precision tool. For this reason, a quality concentricity gauge belongs on your loading bench if you are looking for the Nth degree of accuracy.
We’ve worked with quite a few concentricity gauges. They all have their strengths and weaknesses, but some just didn’t perform well at all with very short cases like the 6BR and 6PPC. One of our regular readers suggested we check out the H&H Concentricity Gauge, made by Bill Herron in Oregon. So far we are very impressed. A 6BR or PPC case doesn’t tip or rock, causing the needle to jump. We were able to get good, repeatable readings off a seated bullet, which wasn’t easy at all with some of the other units. Our friend agreed with our positive assessment of the H&H, saying: “I have four concentricity gauges. Among these tools, the H&H is the least expensive and the easiest to use of those designed for loaded round measurement AND bullet straightening. It is also built like a brick. However, the Sinclair is [probably] the best for looking at the case alone due to the bearing balls and their adjustability.”
The H&H uses an indicator block to eliminate off-center indicator readings. It will accept .22 PPC through .375 length cases. A reversible spindle acts as a pilot for checking neck thickness. Bill Herron says the unit can also re-align bullets, but we didn’t try out that capability. For more info, visit the H&H Industries website, or call Bill at (541) 327-1411.
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Sinclair International has released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
The Accuracy One Concentricity Gauge works with the full range of cartridges — everything from .22LR to .50 BMG. Adjusting the tool for different-length cases is incredibly easy, because the roller blocks (case supports) are held in place by magnets. You just slide the blocks to the desired position — no tools needed! The indicator stand is also held by magnets so it can slide to any position you want along the case body or bullet. And, the indicator can be moved to the front rail and rotated 90°. This way you can measure on the inside of the case neck.
Hornady Reloading Handbook $10.00 with Bullet Purchase
We’ve worked with quite a few concentricity gauges. They all have their strengths and weaknesses, but some just didn’t perform well at all with very short cases like the 6BR and 6PPC. One of our regular readers suggested we check out the 
