The U.S. Army Marksmanship Unit published a series of reloading “how-to” articles on the USAMU Facebook page. A while back the USAMU’s reloading gurus looked at the subject of cartridge run-out and what can be done to produce straighter ammo. Tasked with producing thousands of rounds of ammo for team members, the USAMU’s reloading staff has developed smart methods for improving concentricity, even with budget-priced dies. For other hand-loading tips, visit the USAMU Facebook page.
Minimizing Runout with Standard Seating Dies
This USAMU article explains how to set up standard bullet seating dies dies to minimize Total Indicated Run-out (TIR). The loading process is described using a single-stage press since most handloaders have one. A high-quality run-out gauge is essential for obtaining consistent, accurate results.
Having sized, primed, and charged our brass, the next step is bullet seating. Many approaches are possible; one that works well follows. When setting up a standard seating die, insert a sized, trimmed case into the shellholder and fully raise the press ram. Next, back the seating stem out and screw the die down until the internal crimping shoulder touches the case mouth.
Back the die out ¼ turn from this setting to prevent cartridge crimping. Next, lower the press ram and remove the case. Place a piece of flat steel (or window glass, which is quite flat) on the shellholder and carefully raise the ram.
Place tension on the die bottom with the flat steel on the shellholder. This helps center the die in the press threads. Check this by gently moving the die until it is well-centered. Keeping light tension on the die via the press ram, secure the die lock ring. If one were using a match style, micrometer-type seating die, the next step would be simple: run a charged case with bullet on top into the die and screw the seating stem down to obtain correct cartridge OAL.
However, with standard dies, an additional step can be helpful. When the die has a loosely-threaded seating stem, set the correct seating depth but don’t tighten the stem’s lock nut. Leave a loaded cartridge fully raised into the die to center the seating stem in the die. Then, secure the stem’s lock nut. Next, load sample cartridges and check them to verify good concentricity.
One can also experiment with variations such as letting the seating stem float slightly in the die to self-center, while keeping correct OAL. The run-out gauge will show any effects of changes upon concentricity. However, this method has produced excellent, practical results as evidenced by the experiment cited previously. These results (TIR Study 2) will reproduced below for the reader’s convenience.
First, however, let’s examine run-out figures of some factory-loaded match ammunition. This should give readers who are new to TIR gauges some perspective about the TIR ranges one might encounter.
TIR Study 1: 50 rounds Lake City M852 Match 7.62mm
(168 gr. Sierra MatchKings)
0.000” – 0.001” = 2%
0.001” – 0.002” = 30%
0.002” – 0.003” = 16%
0.003” – 0.004” = 22%
0.004” – 0.005” = 14%
0.005” – 0.006” = 14%
0.006” – 0.007” = 0%
0.007” – 0.008” = 2%
TIR Study 2: 50 rounds of .308 match ammo loaded using carefully-adjusted standard dies, vs. 50 using expensive “Match” dies from the same maker.
Standard dies, TIR:
0.000” — 0.001” = 52%;
0.001”– 0.002” = 40%;
0.002”– 0.003” = 8%.
None greater than 0.003”.
Note: both samples were loaded using the O-Ring method, i.e. with a rubber O-Ring placed under the locking ring of the Full-length sizing die to allow that die to float.
These tips are intended to help shooters obtain the best results from inexpensive, standard loading dies. Especially when using cases previously fired in a concentric chamber, as was done above, top-quality match dies and brass can easily yield ammo with virtually *no* runout, given careful handloading.
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Here’s an inexpensive procedure that can help you load straighter ammo, with slightly better measured concentricity (i.e. less run-out) on the case necks and bullets. Simply use a Rubber O-Ring on the underside of the die locking ring. This allows the die to self-align itself (slightly) to the case that is being sized. Without the O-Ring, if the flat surface on the top of your press is not perfectly square with the thread axis, your die can end up slightly off-angle. This happens when the bottom of the locking ring butts up tight against the top of the press. The O-Ring allows the die to float slightly, and that may, in turn, reduce the amount of run-out induced during case sizing.
Top prone shooter GSArizona, who sadly passed last year, tried this trick and said it works: “Go to your local hardware store and get a #17 O-Ring (that’s the designation at Ace Hardware, don’t know if its universal). Slip the O-Ring on the die and re-adjust the lock ring so that the O-Ring is slightly compressed when the die is at the correct height. Size and measure a few more cases. You will probably see a slight improvement in neck concentricity as the die can now float a bit as the case enters and leaves it. This isn’t going to be a dramatic improvement, but it’s a positive one.”
We want to stress that adding O-Rings to sizing dies may help some reloaders, but we don’t offer this as a panacea. Try it — if using the O-Ring reduces measured runout that’s great. If it doesn’t, you’ve only spent a few pennies to experiment.
Lee Precision makes die lock rings with built-in O-Rings. Lee’s distinctive lock ring design allows the same kind of self-alignment, which is good. However, Lee lock rings don’t clamp in place on the die threads, so they can move when you insert or remove the dies — and that can throw off your die setting slightly. By using an O-Ring under a conventional die lock ring (that can be locked in place), you get the advantages of the Lee design, without the risk of the lock ring moving.
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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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Here’s an inexpensive procedure that can help you load straighter ammo, with slightly better measured concentricity (i.e. less run-out) on the case necks and bullets. Simply use a Rubber O-Ring on the underside of the die locking ring. This allows the die to self-align itself (slightly) to the case that is being sized. Without the O-Ring, if the flat surface on the top of your press is not perfectly square with the thread axis, your die can end up slightly off-angle. This happens when the bottom of the locking ring butts up tight against the top of the press. The O-Ring allows the die to float slightly, and that may, in turn, reduce the amount of run-out induced during case sizing.
Top prone shooter GSArizona has tried this trick and he says it works: “Go to your local hardware store and get a #17 O-Ring (that’s the designation at Ace Hardware, don’t know if its universal). Slip the O-Ring on the die and re-adjust the lock ring so that the O-Ring is slightly compressed when the die is at the correct height. Size and measure a few more cases. You will probably see a slight improvement in neck concentricity as the die can now float a bit as the case enters and leaves it. This isn’t going to be a dramatic improvement, but it’s a positive one.”
We want to stress that adding O-Rings to sizing dies may help some reloaders, but we don’t offer this as a panacea. Try it — if using the O-Ring reduces measured runout that’s great. If it doesn’t, you’ve only spent a few pennies to experiment.
Lee Precision makes die lock rings with built-in O-Rings. Lee’s distinctive lock ring design allows the same kind of self-alignment, which is good. However, Lee lock rings don’t clamp in place on the die threads, so they can move when you insert or remove the dies — and that can throw off your die setting slightly. By using an O-Ring under a conventional die lock ring (that can be locked in place), you get the advantages of the Lee design, without the risk of the lock ring moving.
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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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Each Wednesday, the U.S. Army Marksmanship Unit publishes a reloading “how-to” article on the USAMU Facebook page. A while back the USAMU’s reloading gurus looked at the subject of cartridge run-out and what can be done to produce straighter ammo. Tasked with producing thousands of rounds of ammo for team members, the USAMU’s reloading staff has developed smart methods for improving concentricity, even with budget=price dies. For other hand-loading tips, visit the USAMU Facebook page.
Minimizing Runout with Standard Seating Dies
This USAMU article explains how to set up standard bullet seating dies dies to minimize Total Indicated Run-out (TIR). The loading process is described using a single-stage press since most handloaders have one. A high-quality run-out gauge is essential for obtaining consistent, accurate results.
Having sized, primed, and charged our brass, the next step is bullet seating. Many approaches are possible; one that works well follows. When setting up a standard seating die, insert a sized, trimmed case into the shellholder and fully raise the press ram. Next, back the seating stem out and screw the die down until the internal crimping shoulder touches the case mouth.
Back the die out ¼ turn from this setting to prevent cartridge crimping. Next, lower the press ram and remove the case. Place a piece of flat steel (or window glass, which is quite flat) on the shellholder and carefully raise the ram.
Place tension on the die bottom with the flat steel on the shellholder. This helps center the die in the press threads. Check this by gently moving the die until it is well-centered. Keeping light tension on the die via the press ram, secure the die lock ring. If one were using a match style, micrometer-type seating die, the next step would be simple: run a charged case with bullet on top into the die and screw the seating stem down to obtain correct cartridge OAL.
However, with standard dies, an additional step can be helpful. When the die has a loosely-threaded seating stem, set the correct seating depth but don’t tighten the stem’s lock nut. Leave a loaded cartridge fully raised into the die to center the seating stem in the die. Then, secure the stem’s lock nut. Next, load sample cartridges and check them to verify good concentricity.
One can also experiment with variations such as letting the seating stem float slightly in the die to self-center, while keeping correct OAL. The run-out gauge will show any effects of changes upon concentricity. However, this method has produced excellent, practical results as evidenced by the experiment cited previously. These results (TIR Study 2) will reproduced below for the reader’s convenience.
First, however, let’s examine run-out figures of some factory-loaded match ammunition. This should give readers who are new to TIR gauges some perspective about the TIR ranges one might encounter.
TIR Study 1: 50 rounds Lake City M852 Match 7.62mm
(168 gr. Sierra MatchKings)
0.000” – 0.001” = 2%
0.001” – 0.002” = 30%
0.002” – 0.003” = 16%
0.003” – 0.004” = 22%
0.004” – 0.005” = 14%
0.005” – 0.006” = 14%
0.006” – 0.007” = 0%
0.007” – 0.008” = 2%
TIR Study 2: 50 rounds of .308 match ammo loaded using carefully-adjusted standard dies, vs. 50 using expensive “Match” dies from the same maker.
Standard dies, TIR:
0.000” — 0.001” = 52%;
0.001”– 0.002” = 40%;
0.002”– 0.003” = 8%.
None greater than 0.003”.
Note: both samples were loaded using the O-Ring method, i.e. with a rubber O-Ring placed under the locking ring of the Full-length sizing die to allow that die to float.
These tips are intended to help shooters obtain the best results from inexpensive, standard loading dies. Especially when using cases previously fired in a concentric chamber, as was done above, top-quality match dies and brass can easily yield ammo with virtually *no* runout, given careful handloading.
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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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Here is a simple technique that can potentially help you load straighter ammo, with less run-out (as measured on the bullet). This procedure costs nothing and adds only a few seconds to the time needed to load a cartridge. Next time you’re loading ammo with a threaded (screw-in) seating die, try seating the bullet in two stages. Run the cartridge up in the seating die just enough to seat the bullet half way. Then lower the cartridge and rotate it 180° in the shell-holder. Now raise the cartridge up into the die again and finish seating the bullet.
Steve, aka “Short Range”, one of our Forum members, recently inquired about run-out apparently caused by his bullet-seating process. Steve’s 30BR cases were coming out of his neck-sizer with good concentricity, but the run-out nearly doubled after he seated the bullets. At the suggestion of other Forum members, Steve tried the process of rotating his cartridge while seating his bullet. Steve then measured run-out on his loaded rounds. To his surprise there was a noticeable reduction in run-out on the cases which had been rotated during seating. Steve explains: “For the rounds that I loaded yesterday, I seated the bullet half-way, and turned the round 180 degrees, and finished seating the bullet. That reduced the bullet runout by almost half on most rounds compared to the measurements from the first test.”
Steve recorded run-out measurements on his 30BR brass using both the conventional (one-pass) seating procedure, as well as the two-stage (with 180° rotation) method. Steve’s measurements are collected in the two charts above. As you can see, the run-out was less for the rounds which were rotated during seating. Note, the change is pretty small (less than .001″ on average), but every little bit helps in the accuracy game. If you use a threaded (screw-in) seating die, you might try this two-stage bullet-seating method. Rotating your case in the middle of the seating process won’t cost you a penny, and it just might produce straighter ammo (nothing is guaranteed). If you do NOT see any improvement on the target, you can always go back to seating your bullets in one pass. READ Forum Thread..
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For those who prefer to neck-size their brass (rather than full-length-size), the LEE Collet Die is a popular, inexpensive option. It works by having collet tangs or “fingers” press the neck against a central mandrel. The benefit is that you get a very straight neck, which is sized consistently from top to bottom. Canadian shooter Jerry Teo explains: “LEE Collet Dies produce sized cases with very low runout (measured runout is under .001″ using a Sinclair concentricity gauge). You also don’t get the build-up of brass at the base of the neck, as can happen with bushing neck dies. The neck-shoulder junction stays nice and crisp.”
TIP ONE — Adjusting Tension
LEE Collet dies don’t have a specific mechanical adjustment for neck tension. But you CAN easily modify the die to provide more or less tension. If you want to adjust the neck tension using a Lee Collet die, you can simply chuck the mandrel in a drill and reduce the diameter with some sand-paper (to increase neck tension) or you can order a mandrel the next caliber larger and turn it to whatever diameter you want (the larger the mandrel diameter, the less the neck tension). You can also order custom mandrels from Lee sized to any diameter you want.
Lee also offers Custom Collet Dies, made from two fired cases. Lee offers custom standard collet dies for $78.00 and custom large collet dies for $160.00. CLICK HERE to ORDER.
TIP TWO — Polish and Tune for Easy Case Removal
Some users have complained that their Collet Dies grab the case-neck too firmly, making the case hard to remove. There are solutions to this problem. First inspect the collet fingers and smooth the inner surface up a bit with polishing compound or an extra-fine sanding pad. Second, you can open up the fingers a little bit. LEE recommends that if your Collet Die is sticking, take a steel punch and tap the fingers apart a little bit so that the natural “unloaded” position is wider. Lastly, you should lightly lubricate the outside of the collet fingers (see arrows) before you re-assemble the die. This will ensure they slide smoothly. Also, to prevent the collet fingers from closing too tight, never load up the die with your press without putting a case in place first. Without a case neck between the collet fingers and the mandrel, the collet can clamp itself too tight as you raise the ram.
TIP THREE — Size Twice and Spin Your Case 1/8th Turn
After reaching fully “down” on your press handle, withdraw the case about an inch and manually rotate it about 1/8th (NOT 1/4 or 1/2) turn while still in the shell-holder, then size again. This will place the die’s collet petals on the four “high spots” of the case neck and will result in a rounder, more evenly-sized neck with slightly more bullet tension. This takes only about one second more per case and is well worth the slight extra effort. (We thank reader Stonecreek for this smart tip).
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.
Over the years, many different concentricity tools have been on the market. Various approaches have been taken to straightening rounds that exhibit poor concentricity. With extreme examples of excessive run-out, the bullet is is visibly crooked in the neck with the bullet tip clearly off-center. That’s never a good thing. Straight ammo shoots better.
Straighten-Up and Fly Right
If you could straighten up crooked rounds, accuracy should be improved. In the past, some tools promised more than they delivered. But now Bill Goad, a record-setting benchrest shooter, has invented a new tool that improves concentricity via an impact or “jarring” method. A vertical rod with a curved face mates with the case-neck. You spin the case to find the “high spot” of max eccentricity. Then just tap the rod a couple of times and the neck comes back onto centerline. You can then confirm the concentricity improvement with the dial indicator. Watch the video to see how this is done. Pay particular attention to times 01:25 to 01:45. The case starts at .004″ run-out (01:32). After correction (01:40) the neck shows less than .001″ (one-thousandth) run-out.
Benchrest ace Bill Goad demonstrates his innovative Fli-Right Concentricity gauge tool. It works differently than other concentricity enhancers on the market.
Bill Goad knows something about accuracy. He shot a 10-target 100/200 benchrest Combined Aggregate of 0.178″ (see video at 00:15-00:35). Bill Goad’s tool offers advantages over systems that clamp a cartridge at both ends and try to bend the case or tilt the bullet without straightening the neck. Goad’s new Fli-Right tool is available now from PremierAccuracy.com.
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This article originally appeared in Sinclair Intl’s Reloading Press Blog, which has been merged into the Gun Tech Section on Sinclair’s website, www.SinclairIntl.com
Steps to Minimize Bullet Run-Out
Poor bullet run-out can cause poor and inconsistent accuracy, and variations in bullet velocities. The truer the loaded round, the more consistent your results will be on paper and across the chronograph.
Measuring Concentricity
We all know that low run-out is the goal. But how can you tell if your run-out is high or low? Run-out is generally measured in thousandths of an inch with a concentricity gauge. There are many concentricity gauges to choose from that work well. Some work on loaded rounds only, some have a bullet straightening feature, and a few work on both loaded rounds and empty cases for checking case neck concentricity. The tool of choice for the Sinclair Reloading Tech Staff is the Sinclair Concentricity Gauge (Part # 09-175).
This tool is a mainstay on my bench, and it is used about as much as I use my reloading press! The tool uses two sets of bearings that are set on lateral, length-adjustable anodized aluminum blocks to accommodate cartridges from .221 Fireball-sized cases up to .50 BMG. The indicator is set on a height adjustable swiveling base on a stand that can be used for checking bullet or case neck run-out. The adjustable blocks ride aligned in a precision-milled slot. The entire set up is on an anodized base plate that gives excellent support during the process that is crucial to operation and accuracy. Basically the operation consists of placing a loaded round (for checking bullet run-out) or an empty case (for case run-out) on the bearings with the indicator end touching the chosen point to be measured. The case is easily spun with one finger as the indicator measures the amount of run-out. Once this process has been done a few times it is a fast and accurate means of measurement. In terms of indicator type being used, whether dial or digital, I actually prefer a standard dial indicator over the digital type. My reason for this choice is that you can see the needle jump when run-out is present. I believe this to be easier and faster than looking at digital numbers while measuring. In the video below, Sinclair’s Bill Gravatt shows how to use the Sinclair Concentricity Gauge correctly.
Sizing Steps to Minimize Run-Out
One of the most common steps in the reloading process that contributes to bullet run-out occurs is the sizing operation. If improper techniques are used or there are issues with the sizing die set up, a once perfectly concentric case can become out of whack. By using the proper dies for your application, properly setting up the die/shell holder or floating the de-capping/expander assembly, you can eliminate problems before they happen.
Many of us on the technical staff choose the Redding Type-S series of dies. These are full-Length or neck sizing dies that utilize a removable/changeable neck bushing (sold separately) to size the neck according to your application. These dies are machined with true precision and quality in mind. The Type-S dies come with a standard de-capping assembly with a caliber-specific expander ball in place. In addition to this an undersized retainer to hold the de-capping pin is included with the die. In my experience with these dies I use the standard expander ball with new, unfired brass on the initial re-size. I will then use the undersized retainer in place of the expander ball with brass that has been fired. I have found this step crucial in my reloading regiment to minimize bullet run out. The use of the expander ball can cause a few thousandths of run-out when the case is being pulled back out of the sizing die. With the undersized retainer in place the only thing that touches the neck of the case in sizing is the bushing. If you prefer to use an expander ball, Redding offers caliber specific carbide floating expander balls that fit on the de-capping rod. This free floating expander ball will self center on the case neck, and reduce the amount of run-out that can be caused by a standard expander ball.
When setting up a Type-S sizing die, set the neck bushing into the die with the numbers facing down toward the body of the die. Tighten the de-capping assembly until it contacts the bushing and then back it off ¼ of a turn. This allows the bushing to free float in the die. You should be able to hear the bushing rattle if you shake the die. Having the bushing free floating self centers the neck, and again minimizes any run-out that can occur.
If you prefer other brands of sizing dies there are a few tricks that people use to minimize run-out as well. Many reloaders claim that the use of an O-ring at the base of the de-capping assembly lock nut will float the assembly and help self center during sizing. Another trick that has been used is to remove the retaining pin on the shell holder slot on the press ram, and use an O-ring in its place to hold the shell holder in place. This allows the shell holder to self center during sizing as well.
Seating Steps to Minimize Run-Out
Run-out issues can arise during the bullet seating process. To reduce run-out during seating, use a high-quality die with a sliding sleeve. The sliding sleeve perfectly aligns the case with the bullet to be seated. Good examples of these dies are the Redding Competition Micrometer bullet seating dies, Forster Ultra Seaters, or RCBS Competition Seating dies. All of these dies utilize a micrometer top to precisely set seating depth. They are all very high quality dies that have tight tolerances to maximize bullet straightness during seating.
We receive many questions about seating long pointed bullets such as the Berger VLD or Hornady A-Max. One problem that the reloader faces with longer bullets is that they are so long that the standard seating stem is not machined deep enough to contact these bullets properly. The point of the bullet “bottoms out” in the stem and the result is off-center seating and/or rings and dents on the bullet nose. If you plan on using such bullets, you should purchase a “VLD” style seating stem, which is cut to accommodate the longer bullets. The use of this stem results in truer seating of the bullet without leaving a ring or marring the tip of the bullet.
Besides using a traditional press and threaded seating die, another great way to get a true bullet seat is by using an arbor press and Wilson chamber-type seating die. These dies are cut to very tight tolerances and have proven themselves as the main choice for bench rest enthusiasts. The design of the die positively aligns the case with the bullet as they are both captured by the die before the bullet is pushed straight into the case by the stem. These seating dies are available with the standard seating cap and stem or an additional micrometer top can be added for precise adjustment. Wilson also offers a stainless seating die with an integral micrometer seating head.
Finally another trick used by many in the seating process is to turn the case while the bullet is being seated. Some people claim this will keep things straight. What they do is raise the ram in increments while seating and rotate the case in the shellholder in increments of 90 degrees from the original starting while the bullet is being seated. Personally I have tried this and have seen no significant difference at all. However you may be the judge of this one. It makes sense, and maybe I should try this a little more before I rule it out.
After the Rounds Are Loaded — Batch Sorting by Concentricity Levels
No matter how meticulous you are, and no matter how good your components and tools are, run-out will still show up. Reloaders can drive themselves crazy trying to make each and every loaded round a true “0” in run-out. You will still see some minimal amount no matter what you do. Set yourself a standard of maximum allowable run-out for your loads. For instance for my Long Range 600- and 1000-yard F-Class loads I like to see .002” or less. I average .0015” and see a few in the range up to .004”. I spin each loaded round on my Sinclair Concentricity Gauge and sort them by run-out. Those that run over .002” I use for sighters or practice. Though achieving zero run-out (on every round) isn’t possible, minimizing run-out can definitely help your performance. Not only will your loads shoot better but you will have one less thing to worry about when you are lining up the sights on the target.
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TIP TWO — Polish and Tune for Easy Case Removal
Measuring Concentricity
Many of us on the technical staff choose the Redding Type-S series of dies. These are full-Length or neck sizing dies that utilize a removable/changeable neck bushing (sold separately) to size the neck according to your application. These dies are machined with true precision and quality in mind. The Type-S dies come with a standard de-capping assembly with a caliber-specific expander ball in place. In addition to this an undersized retainer to hold the de-capping pin is included with the die. In my experience with these dies I use the standard expander ball with new, unfired brass on the initial re-size. I will then use the undersized retainer in place of the expander ball with brass that has been fired. I have found this step crucial in my reloading regiment to minimize bullet run out. The use of the expander ball can cause a few thousandths of run-out when the case is being pulled back out of the sizing die. With the undersized retainer in place the only thing that touches the neck of the case in sizing is the bushing. If you prefer to use an expander ball, Redding offers caliber specific carbide floating expander balls that fit on the de-capping rod. This free floating expander ball will self center on the case neck, and reduce the amount of run-out that can be caused by a standard expander ball.
