Over the years, the U.S. Army Marksmanship Unit (USAMU) published a series of reloading articles on its Facebook Page. In this article, the second in a 3-part series, the USAMU covers the process of loading competition pistol ammunition. The authors focus on two key elements — the taper crimp and the quality/uniformity of the original brass. If you shoot pistol competitively, or just want to maximize the accuracy of your handguns, read this article. The taper crimp tips are very important.
Loading Accurate Competition Pistol Ammunition — Part 2 of 3
One often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of taper crimp used, and its effect on accuracy. (NOTE: this article pertains to loading for semi-autos — revolver crimp techniques involve some quite different issues.) Briefly, different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors such as case neck tension. During machine-rest testing of experimental Service Pistol ammunition, many variables are examined. Among these, our Shop often varies a load’s crimp in degrees of 0.001″ when re-testing for finest accuracy.
How to Measure Taper Crimp on Pistol Cartridges
One question that often arises is, “How do I measure the taper crimp I’m putting on my cartridges?” Using the narrow part of one’s dial caliper jaws, carefully measure the case diameter at the exact edge of the case mouth on a loaded cartridge. It’s important to take several measurements to ensure consistency. Also, be sure to measure at several places around the case mouth, as case wall thickness can vary. After measuring 2-3 cartridges with a given crimp setting, one can be confident of the true dimension and that it can be repeated later, if needed.
However, for good results, one must use brass from one maker due to variances in case wall thickness. For example, the same degree of crimp that imparts a measurement of 0.471″ with Brand X brass may result in 0.469″ with Brand Y. Thus, for best accuracy, using brass from the same manufacturer is important — particularly for 50-yard Slow Fire. In a perfect world, it is better still to use brass from one lot number if possible. With the popularity of progressive presses using interchangeable tool heads, keeping separate tool heads adjusted for each load helps maximize uniformity between ammunition lots.
Brass Uniformity and Accuracy
Brass is important to pistol accuracy. While accurate ammunition can be loaded using brass of mixed parentage, that is not conducive to finest results, particularly at 50 yards. It is important for the serious competitor to pay attention to his brass – even if only for the 50-yard “Slow Fire” portions of “Bullseye” matches and practice. By segregating brass as described above, and additionally keeping track of the number of times a given batch of cases has been fired, one can ensure case neck tension and case length are at their most uniform.
Given the large volumes of ammunition consumed by active pistol competitors, using inexpensive, mixed surplus brass for practice, particularly at the “short line” (25 yards), is understandable. In NRA Outdoor Pistol (“Bullseye”), the 10-ring is relatively generous — especially for a well-trained shooter with an accurate pistol and load. However, for the “long line” (50 yards), purchasing and segregating a lot of high-quality brass to be used strictly for slow-fire is a wise idea. To keep track of your brass on the line, use a unique headstamp marking with 1 or 2 colors of marking pen ink.
Uniform Cartridge Overall Length is Important
Cartridge case Overall Length (OAL) uniformity as it comes from the factory is important to achieving utmost accuracy. More uniform case lengths (best measured after sizing) contribute to greater consistency of crimp, neck tension, ignition/burn of powder charge, headspace (rimless cartridges), etc. Cartridge case-length consistency varies noticeably by maker and, with lesser manufacturers, also from lot to lot. Some manufacturers are more consistent in their dimensions than others, and also in the hardness/ductility of their brass. Similarly, pay attention to primer brands, powder lot numbers, etc.
Consider Using a Lock-Out Die with Progressive Presses
When reloading pistol ammo with a Progressive press, we strongly recommend the use of a lock-out die, or other system that can detect double charges or low charges. If your progressive is manually advanced, the possibility of a double charge is very real — and that can have disastrous consequences.
On UltimateReloader.com website you’ll find an excellent two-part series on the function and set-up of the RCBS Lock-Out Die. This die prevents loading if a high or low powder charge is detected. The video below shows setup of the RCBS Lock-Out Die on the Dillon XL-650 progressive press.
The RCBS Lock-Out Die can also be used with some Dillon and Hornady progressive presses.
If you load pistol or rifle ammo with a progressive press, we strongly recommend you get a Lock-Out Die from RCBS. This unique reloading die will prevent your progressive press from advancing if the dispensed powder charge is more or less than about 0.3 grains too high or too low. The Lock-Out Die really works. Your Editor uses it on his RCBS 2000 progressive press. I can affirm that a Lock-Out Die has “saved my bacon” a half-dozen times over the years when there was an over-charge (which could cause a Kaboom) or a low charge (which could cause a squib load).
The Lock-Out Die works by using a central die detection rod that sets its vertical position based on the height of the powder column in the case. Through an ingenious design, if the powder column height is too low or too high, the rod locks in place as you start to pull the press handle. This halts the press before the ram can lift and the cartridge plate can advance. Unlike a beeping alarm system (which can be ignored or defeated), the Lock-Out Die physically stops the movement of the press ram and prevents a bullet being seated in the “problem” case.
It takes a bit of tweaking to get the Lock-Out Die detection rod setting just right, but once it is correctly positioned, the Lock-Out Die works smoothly in the background. The Lock-Out Die won’t interfere with the loading process unless it detects a high or low charge — and then it positively stops the progressive loading cycle.
While crafted for use in RCBS progressive presses, the RCBS Lock-Out Die can also be used on a Dillon XL Progressive (see video below) or Hornady Lock-N-Load progressive — though it does take up one station which could otherwise be used for a final crimp die (after the seating die). The RCBS 2000 has one more station than a Dillon 550/650, so it’s an ideal platform for using the Lock-Out Die.
Learn More at UltimateReloader.com
On the UltimateReloader.com website, run by our friend Gavin Gear, you’ll find an excellent two-part series on the function and set-up of the RCBS Lock-Out Die. Part One explains how the Lock-Out Die functions, using cut-away illustrations. Part Two shows how to install and adjust the Lock-Out Die on various progressive presses. The Ultimate Reloader video at the top of this article shows setup of the RCBS Lock-Out Die on the Dillon XL-650 progressive press, while the Reloading Bench video below shows the Lock-Out Die on a Hornady LnL progressive.
Progressive reloading presses offer shooters speed and efficiency in producing custom-tailored rifle and pistol ammunition. However, there is a wide choice of Progressive Presses and a bewildering array of options to consider. In this video, the 6.5 Guys and UltimateReloader.com’s Gavin Gear provide an overview of the leading Progressive Presses on the market along with key considerations for precision rifle shooters. If you are considering getting a Progessive for rifle ammo reloading, you should watch this informative, 25-minute video.
10 Tips for Reloading Rifle Ammo on a Progressive Press:
1. Make sure the brass is very clean. Don’t mix old range pick-up brass with newer brass.
2. Apply a thin, spray lube to all cases before the sizing/loading cycle.
3. Consider priming your brass separately (with a hand or bench tool) before the operation. Then inspect the primers before loading powder and bullets.
4. Always wear eye protection when loading with the Progressive, particularly if you are priming cases.
5. With masking tape, mark the powder measure/dropper with the powder type and cartridge charge weight. Check the charge mass multiple times (see below).
6. Cycle a few cases, sizing and adding powder but NOT seating bullets. Weigh the powder charges to ensure the powder measure is dispensing the correct charge. Sometimes this will change a couple tenths as it “settles down” after the first few charges.
7. Check the brass for shoulder bump and bullet seating depth carefully for the first few rounds, then check again periodically.
8. Try to maintain a steady pace and operate the handle the same way every time.
9. Visually inspect the powder charge in each case (before bullet seating), and use a lock-out die if your Progressive Press has enough stations.
10. Never, ever mix pistol and rifle powders! If you have previously loaded pistol ammo with your Progressive, make sure ALL the powder (every flake and kernel) is removed from all parts of the powder-dropping system before you add rifle powder.
Visit these sites for more Reloading and Precision Shooting Videos:
The U.S. Army Marksmanship Unit (USAMU) published a series of reloading articles on its Facebook Page. In this article, the second in a 3-part series, the USAMU covers the process of loading competition pistol ammunition. The authors focus on two key elements — the taper crimp and the quality/uniformity of the original brass. If you shoot pistol competitively, or just want to maximize the accuracy of your handguns, read this article. The taper crimp tips are very important.
Loading Accurate Competition Pistol Ammunition — Part 2 of 3
Today, we resume our series on factors affecting accuracy in pistol handloads. Readers who missed Part One can visit our USAMU Facebook Page. [To read the first article in the series, search for March 28, 2018 to find that first installment, which is definitely worth reading.]
One often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of taper crimp used, and its effect on accuracy. (NOTE: this article pertains to loading for semi-autos – revolver crimp techniques involve some quite different issues.) Briefly, different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors such as case neck tension. During machine-rest testing of experimental Service Pistol ammunition, many variables are examined. Among these, our Shop often varies a load’s crimp in degrees of 0.001″ when re-testing for finest accuracy.
How to Measure Taper Crimp on Pistol Cartridges
One question that often arises is, “How do I measure the taper crimp I’m putting on my cartridges?” Using the narrow part of one’s dial caliper jaws, carefully measure the case diameter at the exact edge of the case mouth on a loaded cartridge. It’s important to take several measurements to ensure consistency. Also, be sure to measure at several places around the case mouth, as case wall thickness can vary. After measuring 2-3 cartridges with a given crimp setting, one can be confident of the true dimension and that it can be repeated later, if needed.
However, for good results, one must use brass from one maker due to variances in case wall thickness. For example, the same degree of crimp that imparts a measurement of 0.471″ with Brand X brass may result in 0.469″ with Brand Y. Thus, for best accuracy, using brass from the same manufacturer is important — particularly for 50-yard Slow Fire. In a perfect world, it is better still to use brass from one lot number if possible. With the popularity of progressive presses using interchangeable tool heads, keeping separate tool heads adjusted for each load helps maximize uniformity between ammunition lots.
Brass Uniformity and Accuracy
Brass is important to pistol accuracy. While accurate ammunition can be loaded using brass of mixed parentage, that is not conducive to finest results, particularly at 50 yards. It is important for the serious competitor to pay attention to his brass – even if only for the 50-yard “Slow Fire” portions of “Bullseye” matches and practice. By segregating brass as described above, and additionally keeping track of the number of times a given batch of cases has been fired, one can ensure case neck tension and case length are at their most uniform.
Given the large volumes of ammunition consumed by active pistol competitors, using inexpensive, mixed surplus brass for practice, particularly at the “short line” (25 yards), is understandable. In NRA Outdoor Pistol (“Bullseye”), the 10-ring is relatively generous — especially for a well-trained shooter with an accurate pistol and load. However, for the “long line” (50 yards), purchasing and segregating a lot of high-quality brass to be used strictly for slow-fire is a wise idea. To keep track of your brass on the line, use a unique headstamp marking with 1 or 2 colors of marking pen ink.
Uniform Cartridge Overall Length is Important
Cartridge case Overall Length (OAL) uniformity as it comes from the factory is important to achieving utmost accuracy. More uniform case lengths (best measured after sizing) contribute to greater consistency of crimp, neck tension, ignition/burn of powder charge, headspace (rimless cartridges), etc. Cartridge case-length consistency varies noticeably by maker and, with lesser manufacturers, also from lot to lot. Some manufacturers are more consistent in their dimensions than others, and also in the hardness/ductility of their brass. Similarly, pay attention to primer brands, powder lot numbers, etc.
Consider Using a Lock-Out Die with Progressive Presses
When reloading pistol ammo with a Progressive press, we strongly recommend the use of a lock-out die, or other system that can detect double charges or low charges. If your progressive is manually advanced, the possibility of a double charge is very real — and that can have disastrous consequences.
On UltimateReloader.com website you’ll find an excellent two-part series on the function and set-up of the RCBS Lock-Out Die. This die prevents loading if a high or low powder charge is detected. The video above shows setup of the RCBS Lock-Out Die on the Dillon XL-650 progressive press.
The RCBS Lock-Out Die can also be used with some Dillon and Hornady progressive presses.
If you load pistol or rifle ammo with a progressive press, we strongly recommend you get a Lock-Out Die from RCBS. This unique reloading die will prevent your progressive press from advancing if the dispensed powder charge is more or less than about 0.3 grains too high or too low. The Lock-Out Die really works. Your Editor uses it on his RCBS 2000 progressive press. I can affirm that a Lock-Out Die has “saved my bacon” a half-dozen times over the years when there was an over-charge (which could cause a Kaboom) or a low charge (which could cause a squib load).
The Lock-Out Die works by using a central die detection rod that sets its vertical position based on the height of the powder column in the case. Through an ingenious design, if the powder column height is too low or too high, the rod locks in place as you start to pull the press handle. This halts the press before the ram can lift and the cartridge plate can advance. Unlike a beeping alarm system (which can be ignored or defeated), the Lock-Out Die physically stops the movement of the press ram and prevents a bullet being seated in the “problem” case.
It takes a bit of tweaking to get the Lock-Out Die detection rod setting just right, but once it is correctly positioned, the Lock-Out Die works smoothly in the background. The Lock-Out Die won’t interfere with the loading process unless it detects a high or low charge — and then it positively stops the progressive loading cycle.
While crafted for use in RCBS progressive presses, the RCBS Lock-Out Die can also be used on a Dillon XL Progressive (see video below) or Hornady Lock-N-Load progressive — though it does take up one station which could otherwise be used for a final crimp die (after the seating die). The RCBS 2000 has one more station than a Dillon 550/650, so it’s an ideal platform for using the Lock-Out Die.
Learn More at UltimateReloader.com
On the UltimateReloader.com website, run by our friend Gavin Gear, you’ll find an excellent two-part series on the function and set-up of the RCBS Lock-Out Die. Part One explains how the Lock-Out Die functions, using cut-away illustrations. Part Two shows how to install and adjust the Lock-Out Die on various progressive presses. The Ultimate Reloader video at the top of this article shows setup of the RCBS Lock-Out Die on the Dillon XL-650 progressive press, while the Reloading Bench video below shows the Lock-Out Die on a Hornady LnL progressive.
Progressive reloading presses offer shooters speed and efficiency in producing custom-tailored rifle and pistol ammunition. However, there is a wide choice of Progressive Presses and a bewildering array of options to consider. In this video, the 6.5 Guys and UltimateReloader.com’s Gavin Gear provide an overview of the leading Progressive Presses on the market along with key considerations for precision rifle shooters. If you are considering getting a Progessive for rifle ammo reloading, you should watch this informative, 25-minute video.
10 Tips for Reloading Rifle Ammo on a Progressive Press:
1. Make sure the brass is very clean. Don’t mix old range pick-up brass with newer brass.
2. Apply a thin, spray lube to all cases before the sizing/loading cycle.
3. Consider priming your brass separately (with a hand or bench tool) before the operation. Then inspect the primers before loading powder and bullets.
4. Always wear eye protection when loading with the Progressive, particularly if you are priming cases.
5. With masking tape, mark the powder measure/dropper with the powder type and cartridge charge weight. Check the charge mass multiple times (see below).
6. Cycle a few cases, sizing and adding powder but NOT seating bullets. Weigh the powder charges to ensure the powder measure is dispensing the correct charge. Sometimes this will change a couple tenths as it “settles down” after the first few charges.
7. Check the brass for shoulder bump and bullet seating depth carefully for the first few rounds, then check again periodically.
8. Try to maintain a steady pace and operate the handle the same way every time.
9. Visually inspect the powder charge in each case (before bullet seating), and use a lock-out die if your Progressive Press has enough stations.
10. Never, ever mix pistol and rifle powders! If you have previously loaded pistol ammo with your Progressive, make sure ALL the powder (every flake and kernel) is removed from all parts of the powder-dropping system before you add rifle powder.
Visit these sites for more Reloading and Precision Shooting Videos:
The U.S. Army Marksmanship Unit (USAMU) published a series of reloading articles on its Facebook Page. In this article, the second in a 3-part series, the USAMU covers the process of loading competition pistol ammunition. The authors focus on two key elements — the taper crimp and the quality/uniformity of the original brass. If you shoot pistol competitively, or just want to maximize the accuracy of your handguns, read this article. The taper crimp tips are very important.
Loading Accurate Competition Pistol Ammunition — Part 2 of 3
Today, we resume our series on factors affecting accuracy in pistol handloads. Readers who missed Part One can visit our USAMU Facebook Page. Scroll down to March 28, 2018 to find that first installment which is worth reading.
One often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of taper crimp used, and its effect on accuracy. (NOTE: this article pertains to loading for semi-autos – revolver crimp techniques involve some quite different issues.) Briefly, different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors such as case neck tension. During machine-rest testing of experimental Service Pistol ammunition, many variables are examined. Among these, our Shop often varies a load’s crimp in degrees of 0.001″ when re-testing for finest accuracy.
How to Measure Taper Crimp on Pistol Cartridges
One question that often arises is, “How do I measure the taper crimp I’m putting on my cartridges?” Using the narrow part of one’s dial caliper jaws, carefully measure the case diameter at the exact edge of the case mouth on a loaded cartridge. It’s important to take several measurements to ensure consistency. Also, be sure to measure at several places around the case mouth, as case wall thickness can vary. After measuring 2-3 cartridges with a given crimp setting, one can be confident of the true dimension and that it can be repeated later, if needed.
However, for good results, one must use brass from one maker due to variances in case wall thickness. For example, the same degree of crimp that imparts a measurement of 0.471″ with Brand X brass may result in 0.469″ with Brand Y. Thus, for best accuracy, using brass from the same manufacturer is important — particularly for 50-yard Slow Fire. In a perfect world, it is better still to use brass from one lot number if possible. With the popularity of progressive presses using interchangeable tool heads, keeping separate tool heads adjusted for each load helps maximize uniformity between ammunition lots.
Brass Uniformity and Accuracy
Brass is important to pistol accuracy. While accurate ammunition can be loaded using brass of mixed parentage, that is not conducive to finest results, particularly at 50 yards. It is important for the serious competitor to pay attention to his brass – even if only for the 50-yard “Slow Fire” portions of “Bullseye” matches and practice. By segregating brass as described above, and additionally keeping track of the number of times a given batch of cases has been fired, one can ensure case neck tension and case length are at their most uniform.
Given the large volumes of ammunition consumed by active pistol competitors, using inexpensive, mixed surplus brass for practice, particularly at the “short line” (25 yards), is understandable. In NRA Outdoor Pistol (“Bullseye”), the 10-ring is relatively generous — especially for a well-trained shooter with an accurate pistol and load. However, for the “long line” (50 yards), purchasing and segregating a lot of high-quality brass to be used strictly for slow-fire is a wise idea. To keep track of your brass on the line, use a unique headstamp marking with 1 or 2 colors of marking pen ink.
Uniform Cartridge Overall Length is Important
Cartridge case Overall Length (OAL) uniformity as it comes from the factory is important to achieving utmost accuracy. More uniform case lengths (best measured after sizing) contribute to greater consistency of crimp, neck tension, ignition/burn of powder charge, headspace (rimless cartridges), etc. Cartridge case-length consistency varies noticeably by maker and, with lesser manufacturers, also from lot to lot. Some manufacturers are more consistent in their dimensions than others, and also in the hardness/ductility of their brass. Similarly, pay attention to primer brands, powder lot numbers, etc.
Consider Using a Lock-Out Die with Progressive Presses
When reloading pistol ammo with a Progressive press, we strongly recommend the use of a lock-out die, or other system that can detect double charges or low charges. If your progressive is manually advanced, the possibility of a double charge is very real — and that can have disastrous consequences.
On UltimateReloader.com website you’ll find an excellent two-part series on the function and set-up of the RCBS Lock-Out Die. This die prevents loading if a high or low powder charge is detected. The video above shows setup of the RCBS Lock-Out Die on the Dillon XL-650 progressive press.
The RCBS Lock-Out Die can also be used with some Dillon and Hornady progressive presses.
If you load pistol or rifle ammo with a progressive press, we strongly recommend you get a Lock-Out Die from RCBS. This unique reloading die will prevent your progressive press from advancing if the dispensed powder charge is more or less than about 0.3 grains too high or too low. The Lock-Out Die really works. Your Editor uses it on his RCBS 2000 progressive press. I can affirm that a Lock-Out Die has “saved my bacon” a half-dozen times over the years when there was an over-charge (which could cause a Kaboom) or a low charge (which could cause a squib load).
The Lock-Out Die works by using a central die detection rod that sets its vertical position based on the height of the powder column in the case. Through an ingenious design, if the powder column height is too low or too high, the rod locks in place as you start to pull the press handle. This halts the press before the ram can lift and the cartridge plate can advance. Unlike a beeping alarm system (which can be ignored or defeated), the Lock-Out Die physically stops the movement of the press ram and prevents a bullet being seated in the “problem” case.
It takes a bit of tweaking to get the Lock-Out Die detection rod setting just right, but once it is correctly positioned, the Lock-Out Die works smoothly in the background. The Lock-Out Die won’t interfere with the loading process unless it detects a high or low charge — and then it positively stops the progressive loading cycle.
While crafted for use in RCBS progressive presses, the RCBS Lock-Out Die can also be used on a Dillon XL Progressive (see video below) or Hornady Lock-N-Load progressive — though it does take up one station which could otherwise be used for a final crimp die (after the seating die). The RCBS 2000 has one more station than a Dillon 550/650, so it’s an ideal platform for using the Lock-Out Die.
Learn More at UltimateReloader.com
On the UltimateReloader.com website, run by our friend Gavin Gear, you’ll find an excellent two-part series on the function and set-up of the RCBS Lock-Out Die. Part One explains how the Lock-Out Die functions, using cut-away illustrations. Part Two shows how to install and adjust the Lock-Out Die on various progressive presses. The Ultimate Reloader video at the top of this article shows setup of the RCBS Lock-Out Die on the Dillon XL-650 progressive press, while the Reloading Bench video below shows the Lock-Out Die on a Hornady LnL progressive.
Progressive reloading presses offer shooters speed and efficiency in producing custom-tailored rifle and pistol ammunition. However, there is a wide choice of Progressive Presses and a bewildering array of options to consider. In this video, the 6.5 Guys and UltimateReloader.com’s Gavin Gear provide an overview of the leading Progressive Presses on the market along with key considerations for precision rifle shooters. If you are considering getting a Progessive for rifle ammo reloading, you should watch this informative, 25-minute video.
10 Tips for Reloading Rifle Ammo on a Progressive Press:
1. Make sure the brass is very clean. Don’t mix old range pick-up brass with newer brass.
2. Apply a thin, spray lube to all cases before the sizing/loading cycle.
3. Consider priming your brass separately (with a hand or bench tool) before the operation. Then inspect the primers before loading powder and bullets.
4. Always wear eye protection when loading with the Progressive, particularly if you are priming cases.
5. With masking tape, mark the powder measure/dropper with the powder type and cartridge charge weight. Check the charge mass multiple times (see below).
6. Cycle a few cases, sizing and adding powder but NOT seating bullets. Weigh the powder charges to ensure the powder measure is dispensing the correct charge. Sometimes this will change a couple tenths as it “settles down” after the first few charges.
7. Check the brass for shoulder bump and bullet seating depth carefully for the first few rounds, then check again periodically.
8. Try to maintain a steady pace and operate the handle the same way every time.
9. Visually inspect the powder charge in each case (before bullet seating), and use a lock-out die if your Progressive Press has enough stations.
10. Never, ever mix pistol and rifle powders! If you have previously loaded pistol ammo with your Progressive, make sure ALL the powder (every flake and kernel) is removed from all parts of the powder-dropping system before you add rifle powder.
Visit these sites for more Reloading and Precision Shooting Videos:
The U.S. Army Marksmanship Unit (USAMU) has published a series of reloading articles on its Facebook Page. In this article, the second in a 3-part series, the USAMU covers the process of loading competition pistol ammunition. The authors focus on two key elements — the taper crimp and the quality/uniformity of the original brass. If you shoot pistol competitively, or just want to maximize the accuracy of your handguns, read this article. The taper crimp tips are very important.
Loading Accurate Competition Pistol Ammunition — Part 2 of 3
Today, we resume our series on factors affecting accuracy in pistol handloads. Readers who missed Part One can visit our USAMU Facebook Page. Scroll down to March 28, 2018 to find that first installment which is worth reading.
One often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of taper crimp used, and its effect on accuracy. (NOTE: this article pertains to loading for semi-autos – revolver crimp techniques involve some quite different issues.) Briefly, different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors such as case neck tension. During machine-rest testing of experimental Service Pistol ammunition, many variables are examined. Among these, our Shop often varies a load’s crimp in degrees of 0.001″ when re-testing for finest accuracy.
How to Measure Taper Crimp on Pistol Cartridges
One question that often arises is, “How do I measure the taper crimp I’m putting on my cartridges?” Using the narrow part of one’s dial caliper jaws, carefully measure the case diameter at the exact edge of the case mouth on a loaded cartridge. It’s important to take several measurements to ensure consistency. Also, be sure to measure at several places around the case mouth, as case wall thickness can vary. After measuring 2-3 cartridges with a given crimp setting, one can be confident of the true dimension and that it can be repeated later, if needed.
However, for good results, one must use brass from one maker due to variances in case wall thickness. For example, the same degree of crimp that imparts a measurement of 0.471″ with Brand X brass may result in 0.469″ with Brand Y. Thus, for best accuracy, using brass from the same manufacturer is important — particularly for 50-yard Slow Fire. In a perfect world, it is better still to use brass from one lot number if possible. With the popularity of progressive presses using interchangeable tool heads, keeping separate tool heads adjusted for each load helps maximize uniformity between ammunition lots.
Brass Uniformity and Accuracy
Brass is important to pistol accuracy. While accurate ammunition can be loaded using brass of mixed parentage, that is not conducive to finest results, particularly at 50 yards. It is important for the serious competitor to pay attention to his brass – even if only for the 50-yard “Slow Fire” portions of “Bullseye” matches and practice. By segregating brass as described above, and additionally keeping track of the number of times a given batch of cases has been fired, one can ensure case neck tension and case length are at their most uniform.
Given the large volumes of ammunition consumed by active pistol competitors, using inexpensive, mixed surplus brass for practice, particularly at the “short line” (25 yards), is understandable. In NRA Outdoor Pistol (“Bullseye”), the 10-ring is relatively generous — especially for a well-trained shooter with an accurate pistol and load. However, for the “long line” (50 yards), purchasing and segregating a lot of high-quality brass to be used strictly for slow-fire is a wise idea. To keep track of your brass on the line, use a unique headstamp marking with 1 or 2 colors of marking pen ink.
Uniform Cartridge Overall Length is Important
Cartridge case Overall Length (OAL) uniformity as it comes from the factory is important to achieving utmost accuracy. More uniform case lengths (best measured after sizing) contribute to greater consistency of crimp, neck tension, ignition/burn of powder charge, headspace (rimless cartridges), etc. Cartridge case-length consistency varies noticeably by maker and, with lesser manufacturers, also from lot to lot. Some manufacturers are more consistent in their dimensions than others, and also in the hardness/ductility of their brass. Similarly, pay attention to primer brands, powder lot numbers, etc.
Consider Using a Lock-Out Die with Progressive Presses
When reloading pistol ammo with a Progressive press, we strongly recommend the use of a lock-out die, or other system that can detect double charges or low charges. If your progressive is manually advanced, the possibility of a double charge is very real — and that can have disastrous consequences.
On UltimateReloader.com website you’ll find an excellent two-part series on the function and set-up of the RCBS Lock-Out Die. This die prevents loading if a high or low powder charge is detected. The video below shows setup of the RCBS Lock-Out Die on the Dillon XL-650 progressive press.
If you load pistol or rifle ammo with a progressive press, we strongly recommend you get a Lock-Out Die from RCBS. This unique reloading die will prevent your progressive press from advancing if the dispensed powder charge is more or less than about 0.3 grains too high or too low. The Lock-Out Die really works. Your Editor uses it on his RCBS 2000 progressive press. I can affirm that a Lock-Out Die has “saved my bacon” a half-dozen times over the years when there was an over-charge (which could cause a Kaboom) or a low charge (which could cause a squib load).
