Before you load that nice new cartridge brass for the first time, run an expander mandrel down the case necks. This will iron out dents and provide more uniform neck tension. Chose a mandrel diameter that provides appropriate neck tension.
Lapua brass is so good that you’ll be tempted to just load and shoot, if you have a “no-turn” chamber. However, some minimal case prep will ensure more uniform neck tension. Keeping your neck tension very uniform allows more consistent bullet seating. That, in turn, usually yields better accuracy, and lower Extreme Spread and Standard Deviation (ES/SD). Lapua brass, particularly 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win comes from the factory with tighter-than-optimal necks. Before you seat bullets, at a minimum, you should inside chamfer the case mouths, after running an expander mandrel down the necks. The expander mandrels from both Sinclair Int’l and K&M will both leave the necks with enough neck tension (more than .001″) so you can then seat bullets without another operation. We suggest putting a bit of lube on the mandrel before running it down the necks — but remove any lube that gets inside the necks before seating bullets.
Both Sinclair and K&M Tools make a die body specifically to hold expander mandrels. The Sinclair version, is shown above. This $45.99 unit fits caliber-specific expander mandrels ($10.99) which measure approximately .001″ less than bullet diameter for each caliber. This is an updated “Gen II” design that completely captures the mandrel within the die so the mandrel cannot pull out. It also has an O-ring in the die cap that allows the mandrel to self-center within the case neck. Brownells offers two sizes of Sinclair die bodies for expander mandrels: .17 -.338 Caliber (#749011715 $45.99); and .357 – .50 caliber (#749008843, $45.99). All Generation II dies are machined from stainless steel and the standard diameter 7/8-14 dies include the Sinclair Stainless Steel Split Lock Ring.
Once you run the Sinclair expander mandrel down the necks of Lapua brass, after you account for brass spring-back, you’ll have about .002″ neck tension*. This will make the process of seating bullets go much more smoothly, and you will also iron out any dents in the case mouths. Once the case mouths are all expanded, and uniformly round, then do your inside neck chamfering/deburring. The same expander mandrels can be used to “neck-up” smaller diameter brass, or prepare brass for neck-turning.
Forum member Mike Crawford adds: “These expanders can also reduce runout from offset seating. Prior to bullet seating, expand the sized necks to force thickness variance outward. With the Sinclair system, the necks will springback fine, and will not be pulled out of center. This leaves plenty of tension, and bullets seated more centered. I do this, even with turned necks, to get improved seating.”
Mandrels vs. Expander Balls on Decapping Rods
If you haven’t acquired an appropriate expander mandrel for your brass, but you DO have a full-length sizing die with an expander ball, this will also function to “iron out” the necks and reduce tension. However, using a die with an expander ball will work the necks more — since you first size them down, then the ball expands them up again. Typically (but not always), run-out is worse when using an expander ball vs. an expander mandrel.
* This .002″ tension is what we have observed with Lapua 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win brass. This might vary with much smaller or larger cases, and of course a different brand of brass might yield different results. If you get too little tension with your current mandrel, you can get a smaller-diameter mandrel from 21st Century Shooting. 21st Century even offers low-friction Titanium Nitride-coated mandrels.
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Before you load that new cartridge brass for the first time, run an expander mandrel down the case necks. This will iron out dents and provide more uniform neck tension. Chose a mandrel diameter that provides appropriate neck tension.
Lapua brass is so good that you’ll be tempted to just load and shoot, if you have a “no-turn” chamber. However, some minimal case prep will ensure more uniform neck tension. Keeping your neck tension very uniform allows more consistent bullet seating. That, in turn, usually yields better accuracy, and lower Extreme Spread and Standard Deviation (ES/SD). Lapua brass, particularly 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win comes from the factory with tighter-than-optimal necks. Before you seat bullets, at a minimum, you should inside chamfer the case mouths, after running an expander mandrel down the necks. The expander mandrels from both Sinclair Int’l (Brownells) and K&M will both leave the necks with enough neck tension (more than .001″) so you can then seat bullets without another operation. We suggest putting a bit of lube on the mandrel before running it down the necks — but remove any lube that gets inside the necks before seating bullets.
Both Sinclair and K&\M Tools make a die body specifically to hold expander mandrels. The Sinclair version, is shown above. This $37.99 unit fits caliber-specific expander mandrels which measure approximately .001″ less than bullet diameter for each caliber. This is an updated “Gen II” design that completely captures the mandrel within the die so the mandrel cannot pull out. It also has an O-ring in the die cap that allows the mandrel to self-center within the case neck. Sinclair now offers three sizes of die bodies for expander mandrels: .17 -.338 Caliber (#749-011-715WS, $53.99); .357 – .50 caliber (#749-008-843WS, $37.99), and a special .50 Cal die body for large-diameter 50 BMG presses (#749-009-163WS, $51.99). All Generation II dies are machined from stainless steel and the standard diameter 7/8-14 dies include the Sinclair Stainless Steel Split Lock Ring.
Once you run the Sinclair expander mandrel down the necks of Lapua brass, after you account for brass spring-back, you’ll have about .002″ neck tension*. This will make the process of seating bullets go much more smoothly, and you will also iron out any dents in the case mouths. Once the case mouths are all expanded, and uniformly round, then do your inside neck chamfering/deburring. The same expander mandrels can be used to “neck-up” smaller diameter brass, or prepare brass for neck-turning.
Forum member Mike Crawford adds: “These expanders can also reduce runout from offset seating. Prior to bullet seating, expand the sized necks to force thickness variance outward. With the Sinclair system, the necks will springback fine, and will not be pulled out of center. This leaves plenty of tension, and bullets seated more centered. I do this, even with turned necks, to get improved seating.”
Mandrels vs. Expander Balls on Decapping Rods
If you haven’t acquired an appropriate expander mandrel for your brass, but you DO have a full-length sizing die with an expander ball, this will also function to “iron out” the necks and reduce tension. However, using a die with an expander ball will work the necks more — since you first size them down, then the ball expands them up again. Typically (but not always), run-out is worse when using an expander ball vs. an expander mandrel.
* This .002″ tension is what we have observed with Lapua 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win brass. This might vary with much smaller or larger cases, and of course a different brand of brass might yield different results. If you get too little tension with your current mandrel, you can get a smaller-diameter mandrel from 21st Century Innovation, with stainless, Black Nitride, or Titanium nitride versions. The Nitride models have less friction.
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Here’s good news for 30BR shooters. Paul Parosky, maker of the excellent PRP Custom Bullets, is now offering 30BR neck-turned brass. This can save you considerable time and effort forming 30BR cases from Lapua 6mmBR brass. And the neck-turning is superb, again representing time savings (and no tools to buy). You can order this 30BR brass from PRPbullets.com. If you communicate with the PRP team, Paul may be able to neck-turn to your specific thickness. Paul notes: “Here are necks turned for a 0.330 neck. I’ll try my best to accommodate anyone’s neck dimensions as they wish. Just contact us through our website PRPBullets.com.”
About this Neck-Turning set-up — Paul Parosky notes: “For neck-turning I’m using an old drill press that has been re-worked. The cutter and spindle are all indicated before neck turning to ensure no runout. The RPM is around 520. The lube I use is a mixture of royal and mystery oil.”
Why the 30 BR Dominates 100/200 Benchrest for Score Competition
The 30BR, along with some wildcat variants, remains the dominant cartridge in short-range (100/200) benchrest-for-score competition. The 30BR’s .308″-diameter bullets are larger than the 6mm bullets used by the 6PPC (which rules group BR competition). The bigger 30-Cal diameter has an advantage in touching scoring rings. In addition, the 30BR is also relatively easy to tune, and barrel life is considerably better than with smaller-caliber benchrest cartridges. For more information, see our AccurateShooter 30BR Cartridge Guide.
Cases are Expanded, Then Neck-Turned
To produce his 30BR brass, Parosky first uses a series of expander mandrels. Then he neck-turns with power using a converted drill press. Paul tells us: “This is done the old school way, I use three different tapered expander mandrels, then neck-turn it to the proper neck chamber, then run them up through a FL expander mandrel to ensure necks are straight. Then I clean all the cases.”
Paul Parosky Can Also Neck-Turn 6PPC Brass
Paul Parosky also expands and neck-turns 6PPC cases that are made from parent Lapua .220 Russian cartridge brass. Here, illustrating his 6PPC neck-turning operation, is a Paul Parosky post on the USA Benchrest & Extreme Precision Shooters Facebook page.
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Have you ever expanded a .22 or 6mm cartridge all the way up to .30-caliber? If so, you know this can be a difficult procedure that stresses the case necks and neck-shoulder junction. A significant neck-size expansion done in one big jump can increase run-out, cause doughnuts, or worse yet, even split the brass. Therefore you want to proceed in increments, increasing the neck diameter in stages. One smart way to do that is to use a Progressive Press. This article explains how…
The most successful short-range benchrest-for-score cartridge is the 30 BR. That cartridge, as well as 30 BR variants such as the 30 BRX, all start with the 6mmBR Norma parent cartridge, typically with Lapua 6mmBR brass. To get a nice 30 BR case you want to expand in stages, increasing the inside neck diameter incrementally from .243 to .308.
Darrell Jones of DJ’s Brass Service creates thousands of 30 BR cases each year. He has found a clever way to speed up the process — Darrell uses a Progressive Press. He runs his 6BR brass through four (4) separate Hornady neck-sizing dies with expander mandrels. First there is a .257 die, followed by .264 (6.5mm), .284 (7mm), and then .308. Then a fifth and final K&M die provides one last, slight expansion so the newly-fashioned 30 BR cases perfectly fit the arbor of Darrell’s neck-turning tool.
So to repeat, the case starts as .243 (6mm), then moves in up stages .257, .264, .284, and .308, with a final “finishing” step prior to neck-turning. You can see the expansion in this video, which starts with 6mmBR brass that was first hydro-formed to 6 BRX:
Watch 6mm Cases Expanded to 30-Caliber (6BRX to 30 BRX)
For this demo video, Darrell expands just one case at a time. However, he can also put multiple cases in the progressive — one per station. This takes a little more effort, Darrell says, but the results are still excellent. Darrell tells us: “I do put multiple cases in the progressive to save time. The results are the same — I just wanted to show a single-step process and how it reduces run-out by not stressing the shoulder with one big expansion from 6mm straight to 30 caliber. Doing the operation in multiple stages avoids binds and helps keep the shoulders concentric.”
This same multi-stage procedure can be use to expand other cartridge types. For example you could take .221 Fireball brass in stages up to .308 to create 300 Blackout brass.
Darrell uses caliber-specific, Hornady neck-sizing-only dies with elliptical expanders. Darrell tells us: “The Hornady elliptical expander has a reduced bearing surface that puts less strain on the brass when expanding the necks to the next size.” The fitting at the bottom of the die is the Lock-N-Load die bushing that allows fast die changes.
These particular cases used in the video were first hydro-formed to 6BRX then expanded to 30 BRX before neck turning. DJ’s Brass offers hydro-forming for many popular wildcat cartridges such as 6 PPC, 6mm Dasher, and .284 Shehane.
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Here’s good news for 30BR shooters. Paul Parosky, maker of the excellent PRP Custom Bullets, is now offering 30BR neck-turned brass. This can save you considerable time and effort forming 30BR cases from Lapua 6mmBR brass. And the neck-turning is superb, again representing time save (and no tools to buy). You will soon be able to order this 30BR brass from Bruno Shooters Supply. If you communicate with Amy at Bruno’s, Paul may be able to neck-turn to your specific thickness. Paul notes: “Here are necks turned for a 0.330 neck. I’ll try my best to accommodate anyone’s neck dimensions as they wish. Just message Amy Bruno Parosky (at Bruno’s) for details.”
About this Neck-Turning set-up — Paul Parosky notes: “For neck-turning I’m using an old drill press that has been re-worked. The cutter and spindle are all indicated before neck turning to ensure no runout. The RPM is around 520. The lube I use is a mixture of royal and mystery oil.”
Why the 30 BR Dominates 100/200 Benchrest for Score Competition
The 30BR, along with some wildcat variants, remains the dominant cartridge in short-range (100/200) benchrest-for-score competition. The 30BR’s .308″-diameter bullets are larger than the 6mm bullets used by the 6PPC (which rules group BR competition). The bigger 30-Cal diameter has an advantage in touching scoring rings. In addition, the 30BR is also relatively easy to tune, and barrel life is considerably better than with smaller-caliber benchrest cartridges. For more information, see our AccurateShooter 30BR Cartridge Guide.
Cases are Expanded, Then Neck-Turned
To produce his 30BR brass, Parosky first uses a series of expander mandrels. Then he neck-turns with power using a converted drill press. Paul tells us: “This is done the old school way, I use three different tapered expander mandrels, then neck-turn it to the proper neck chamber, then run them up through a FL expander mandrel to ensure necks are straight. Then I clean all the cases.”
Paul Parosky Can Also Neck-Turn 6PPC Brass
Paul Parosky also expands and neck-turns 6PPC cases that are made from parent Lapua .220 Russian cartridge brass. Here, illustrating his 6PPC neck-turning operation, is a Paul Parosky post on the USA Benchrest & Extreme Precision Shooters Facebook page.
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Before you load that nice new cartridge brass for the first time, run an expander mandrel down the case necks. This will iron out dents and provide more uniform neck tension. Chose a mandrel diameter that provides appropriate neck tension.
Lapua brass is so good that you’ll be tempted to just load and shoot, if you have a “no-turn” chamber. However, some minimal case prep will ensure more uniform neck tension. Keeping your neck tension very uniform allows more consistent bullet seating. That, in turn, usually yields better accuracy, and lower Extreme Spread and Standard Deviation (ES/SD). Lapua brass, particularly 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win comes from the factory with tighter-than-optimal necks. Before you seat bullets, at a minimum, you should inside chamfer the case mouths, after running an expander mandrel down the necks. The expander mandrels from both Sinclair Int’l and K&M will both leave the necks with enough neck tension (more than .001″) so you can then seat bullets without another operation. We suggest putting a bit of lube on the mandrel before running it down the necks — but remove any lube that gets inside the necks before seating bullets.
Both Sinclair and K&M Tools make a die body specifically to hold expander mandrels. The Sinclair version, is shown above. This $32.99 unit fits caliber-specific expander mandrels ($9.99) which measure approximately .001″ less than bullet diameter for each caliber. This is an updated “Gen II” design that completely captures the mandrel within the die so the mandrel cannot pull out. It also has an O-ring in the die cap that allows the mandrel to self-center within the case neck. Sinclair now offers three sizes of die bodies for expander mandrels: .17 -.338 Caliber (#749-011-715WS); .357 – .50 caliber (#749-008-843WS), and a special .50 Cal die body for large-diameter 50 BMG presses (#749-009-163WS, $39.99). All Generation II dies are machined from stainless steel and the standard diameter 7/8-14 dies include the Sinclair Stainless Steel Split Lock Ring.
Once you run the Sinclair expander mandrel down the necks of Lapua brass, after you account for brass spring-back, you’ll have about .002″ neck tension*. This will make the process of seating bullets go much more smoothly, and you will also iron out any dents in the case mouths. Once the case mouths are all expanded, and uniformly round, then do your inside neck chamfering/deburring. The same expander mandrels can be used to “neck-up” smaller diameter brass, or prepare brass for neck-turning.
Forum member Mike Crawford adds: “These expanders can also reduce runout from offset seating. Prior to bullet seating, expand the sized necks to force thickness variance outward. With the Sinclair system, the necks will springback fine, and will not be pulled out of center. This leaves plenty of tension, and bullets seated more centered. I do this, even with turned necks, to get improved seating.”
Mandrels vs. Expander Balls on Decapping Rods
If you haven’t acquired an appropriate expander mandrel for your brass, but you DO have a full-length sizing die with an expander ball, this will also function to “iron out” the necks and reduce tension. However, using a die with an expander ball will work the necks more — since you first size them down, then the ball expands them up again. Typically (but not always), run-out is worse when using an expander ball vs. an expander mandrel.
* This .002″ tension is what we have observed with Lapua 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win brass. This might vary with much smaller or larger cases, and of course a different brand of brass might yield different results. If you get too little tension with your current mandrel, you can get a smaller-diameter mandrel from 21st Century Shooting. 21st Century even offers low-friction Titanium Nitride-coated mandrels.
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Here’s good news for 30BR shooters. Paul Parosky, maker of the excellent PRP Custom Bullets, is now offering 30BR neck-turned brass. This can save you considerable time and effort forming 30BR cases from Lapua 6mmBR brass. And the neck-turning is superb, again representing time save (and no tools to buy). You will soon be able to order this 30BR brass from Bruno Shooters Supply. If you communicate with Amy at Bruno’s, Paul may be able to neck-turn to your specific thickness. Paul notes: “Here are necks turned for a 0.330 neck. I’ll try my best to accommodate anyone’s neck dimensions as they wish. Just message Amy Bruno Parosky (at Bruno’s) for details.”
About this Neck-Turning set-up — Paul Parosky notes: “For neck-turning I’m using an old drill press that has been re-worked. The cutter and spindle are all indicated before neck turning to ensure no runout. The RPM is around 520. The lube I use is a mixture of royal and mystery oil.”
Why the 30 BR Dominates 100/200 Benchrest for Score Competition
The 30BR, along with some wildcat variants, remains the dominant cartridge in short-range (100/200) benchrest-for-score competition. The 30BR’s .308″-diameter bullets are larger than the 6mm bullets used by the 6PPC (which rules group BR competition). The bigger 30-Cal diameter has an advantage in touching scoring rings. In addition, the 30BR is also relatively easy to tune, and barrel life is considerably better than with smaller-caliber benchrest cartridges. For more information, see our AccurateShooter 30BR Cartridge Guide.
Cases are Expanded, Then Neck-Turned
To produce his 30BR brass, Parosky first uses a series of expander mandrels. Then he neck-turns with power using a converted drill press. Paul tells us: “This is done the old school way, I use three different tapered expander mandrels, then neck-turn it to the proper neck chamber, then run them up through a FL expander mandrel to ensure necks are straight. Then I clean all the cases.”
Paul Parosky Can Also Neck-Turn 6PPC Brass
Paul Parosky also expands and neck-turns 6PPC cases that are made from parent Lapua .220 Russian cartridge brass. Here, illustrating his 6PPC neck-turning operation, is a recent Paul Parosky post on the USA Benchrest & Extreme Precision Shooters Facebook page.
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Before you load that nice new cartridge brass for the first time, run an expander mandrel down the case necks. This will iron out dents and provide more uniform neck tension. Chose a mandrel diameter that provides appropriate neck tension.
Lapua brass is so good that you’ll be tempted to just load and shoot, if you have a “no-turn” chamber. However, some minimal case prep will ensure more uniform neck tension. Keeping your neck tension very uniform allows more consistent bullet seating. That, in turn, usually yields better accuracy, and lower Extreme Spread and Standard Deviation (ES/SD). Lapua brass, particularly 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win comes from the factory with tighter-than-optimal necks. Before you seat bullets, at a minimum, you should inside chamfer the case mouths, after running an expander mandrel down the necks. The expander mandrels from both Sinclair Int’l and K&M will both leave the necks with enough neck tension (more than .001″) so you can then seat bullets without another operation. We suggest putting a bit of lube on the mandrel before running it down the necks — but remove any lube that gets inside the necks before seating bullets.
Both Sinclair and K&M Tools make a die body specifically to hold expander mandrels. The Sinclair version, is shown above. This $32.99 unit fits caliber-specific expander mandrels ($9.99) which measure approximately .001″ less than bullet diameter for each caliber. This is an updated “Gen II” design that completely captures the mandrel within the die so the mandrel cannot pull out. It also has an O-ring in the die cap that allows the mandrel to self-center within the case neck. Sinclair now offers three sizes of die bodies for expander mandrels: .17 -.338 Caliber (#749-011-715WS $32.99); .357 – .50 caliber (#749-008-843WS, $32.99), and a special .50 Cal die body for large-diameter 50 BMG presses (#749-009-163WS, $39.99). All Generation II dies are machined from stainless steel and the standard diameter 7/8-14 dies include the Sinclair Stainless Steel Split Lock Ring.
Once you run the Sinclair expander mandrel down the necks of Lapua brass, after you account for brass spring-back, you’ll have about .002″ neck tension*. This will make the process of seating bullets go much more smoothly, and you will also iron out any dents in the case mouths. Once the case mouths are all expanded, and uniformly round, then do your inside neck chamfering/deburring. The same expander mandrels can be used to “neck-up” smaller diameter brass, or prepare brass for neck-turning.
Forum member Mike Crawford adds: “These expanders can also reduce runout from offset seating. Prior to bullet seating, expand the sized necks to force thickness variance outward. With the Sinclair system, the necks will springback fine, and will not be pulled out of center. This leaves plenty of tension, and bullets seated more centered. I do this, even with turned necks, to get improved seating.”
Mandrels vs. Expander Balls on Decapping Rods
If you haven’t acquired an appropriate expander mandrel for your brass, but you DO have a full-length sizing die with an expander ball, this will also function to “iron out” the necks and reduce tension. However, using a die with an expander ball will work the necks more — since you first size them down, then the ball expands them up again. Typically (but not always), run-out is worse when using an expander ball vs. an expander mandrel.
* This .002″ tension is what we have observed with Lapua 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win brass. This might vary with much smaller or larger cases, and of course a different brand of brass might yield different results. If you get too little tension with your current mandrel, you can get a smaller-diameter mandrel from 21st Century Shooting. 21st Century even offers low-friction Titanium Nitride-coated mandrels.
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Have you ever expanded a .22 or 6mm cartridge all the way up to .30-caliber? If so, you know this can be a difficult procedure that stresses the case necks and neck-shoulder junction. A significant neck-size expansion done in one big jump can increase run-out, cause doughnuts, or worse yet, even split the brass. Therefore you want to proceed in increments, increasing the neck diameter in stages. One smart way to do that is to use a Progressive Press. This article explains how…
The most successful short-range benchrest-for-score cartridge is the 30 BR. That cartridge, as well as 30 BR variants such as the 30 BRX, all start with the 6mmBR Norma parent cartridge, typically with Lapua 6mmBR brass. To get a nice 30 BR case you want to expand in stages, increasing the inside neck diameter incrementally from .243 to .308.
Darrell Jones of DJ’s Brass Service creates thousands of 30 BR cases each year. He has found a clever way to speed up the process — Darrell uses a Progressive Press. He runs his 6BR brass through four (4) separate Hornady neck-sizing dies with expander mandrels. First there is a .257 die, followed by .264 (6.5mm), .284 (7mm), and then .308. Then a fifth and final K&M die provides one last, slight expansion so the newly-fashioned 30 BR cases perfectly fit the arbor of Darrell’s neck-turning tool.
So to repeat, the case starts as .243 (6mm), then moves in up stages .257, .264, .284, and .308, with a final “finishing” step prior to neck-turning. You can see the expansion in this video, which starts with 6mmBR brass that was first hydro-formed to 6 BRX:
Watch 6mm Cases Expanded to 30-Caliber (6BRX to 30 BRX)
For this demo video, Darrell expands just one case at a time. However, he can also put multiple cases in the progressive — one per station. This takes a little more effort, Darrell says, but the results are still excellent. Darrell tells us: “I do put multiple cases in the progressive to save time. The results are the same — I just wanted to show a single-step process and how it reduces run-out by not stressing the shoulder with one big expansion from 6mm straight to 30 caliber. Doing the operation in multiple stages avoids binds and helps keep the shoulders concentric.”
This same multi-stage procedure can be use to expand other cartridge types. For example you could take .221 Fireball brass in stages up to .308 to create 300 Blackout brass.
Darrell uses caliber-specific, Hornady neck-sizing-only dies with elliptical expanders. Darrell tells us: “The Hornady elliptical expander has a reduced bearing surface that puts less strain on the brass when expanding the necks to the next size.” The fitting at the bottom of the die is the Lock-N-Load die bushing that allows fast die changes.
These particular cases used in the video were first hydro-formed to 6BRX then expanded to 30 BRX before neck turning. DJ’s Brass offers hydro-forming for many popular wildcat cartridges such as 6 PPC, 6mm Dasher, and .284 Shehane.
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You can benefit from these precision mandrels, trust us…
Controlling cartridge neck tension is a critical aspect of accurate reloading. A very small change in the amount of grip on the bullet can actually have a noticeable effect on accuracy (and group size). You can tune neck tension with different size bushings used with FL-sizing or neck-sizing dies. You can also adjust neck “grip” by annealing your brass, or turning your necks for reduced neck-wall thickness.
But perhaps the most precise way to tune neck grip on the bullet is to use Precision Expander Mandrels. Many top shooters size their case necks down pretty far with a full-length sizing die then use a precision neck mandrel as a final step. This expands the neck back to the precisely-desired neck diameter. Because you are working from the “inside out”, variances in neck-wall thickness become less important. This also ensures you have a perfectly-round internal neck geometry for seating your bullet. (Yes, unfortunately some neck bushings are not perfectly round inside.)
For guys who want ultra-precise control over neck tension (and “grip” on the bullet), 21st Century Shooting now offers Precision Expander Mandrels in .0005 (one-half thousandth) increments. These will be available for most popular match calibers including: .224, 6mm, .25, 6.5mm, .270, 7mm, .308, and .338 calibers. These mandrels cost $17.99 each, or you can get a complete set of nine mandrels in .0005 increments (for one caliber) for $144.99. Listed below are the nine 6mm mandrels:
John Perkins, owner of 21st Century tells us: “Finally! We have our expander mandrels up and ready to order on our website here: http://www.xxicsi.com/expander-mandrels.html.” This is a big deal. James Crofts, past National F-TR Champion, says “WooHoo — great news!”
To get best results with these precision mandrels, John recommends using the 21st Century Expander Die Body, part #904. Watch video for set-up tips:
John adds: “We are still in the midst of turning all of these so some calibers will ship when they are completed. Should have them all done by end of next week or so! Thanks for your patience while we got these set up and in process!”
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Before you load that nice new cartridge brass for the first time, run an expander mandrel down the case necks. This will iron out dents and provide more uniform neck tension. Chose a mandrel diameter that provides appropriate neck tension.
Lapua brass is so good that you’ll be tempted to just load and shoot, if you have a “no-turn” chamber. However, some minimal case prep will ensure more uniform neck tension. Keeping your neck tension very uniform allows more consistent bullet seating. That, in turn, usually yields better accuracy, and lower Extreme Spread and Standard Deviation (ES/SD). Lapua brass, particularly 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win comes from the factory with tighter-than-optimal necks. Before you seat bullets, at a minimum, you should inside chamfer the case mouths, after running an expander mandrel down the necks. The expander mandrels from both Sinclair Int’l and K&M will both leave the necks with enough neck tension (more than .001″) so you can then seat bullets without another operation. We suggest putting a bit of lube on the mandrel before running it down the necks — but remove any lube that gets inside the necks before seating bullets.
Both Sinclair and K&M Tools make a die body specifically to hold expander mandrels. The Sinclair version, is shown above. This $28.99 unit fits caliber-specific expander mandrels ($9.99) which measure approximately .001″ less than bullet diameter for each caliber. This is an updated “Gen II” design that completely captures the mandrel within the die so the mandrel cannot pull out. It also has an O-ring in the die cap that allows the mandrel to self-center within the case neck. Sinclair now offers three sizes of die bodies for expander mandrels: .17 -.338 Caliber (#749-011-715WS); .357 – .50 caliber (#749-008-843WS), and a special .50 Cal die body for large-diameter 50 BMG presses (#749-009-163WS, $39.99). All Generation II dies are machined from stainless steel and the standard diameter 7/8-14 dies include the Sinclair Stainless Steel Split Lock Ring.
Once you run the Sinclair expander mandrel down the necks of Lapua brass, after you account for brass spring-back, you’ll have about .002″ neck tension*. This will make the process of seating bullets go much more smoothly, and you will also iron out any dents in the case mouths. Once the case mouths are all expanded, and uniformly round, then do your inside neck chamfering/deburring. The same expander mandrels can be used to “neck-up” smaller diameter brass, or prepare brass for neck-turning.
Forum member Mike Crawford adds: “These expanders can also reduce runout from offset seating. Prior to bullet seating, expand the sized necks to force thickness variance outward. With the Sinclair system, the necks will springback fine, and will not be pulled out of center. This leaves plenty of tension, and bullets seated more centered. I do this, even with turned necks, to get improved seating.”
Mandrels vs. Expander Balls on Decapping Rods
If you haven’t acquired an appropriate expander mandrel for your brass, but you DO have a full-length sizing die with an expander ball, this will also function to “iron out” the necks and reduce tension. However, using a die with an expander ball will work the necks more — since you first size them down, then the ball expands them up again. Typically (but not always), run-out is worse when using an expander ball vs. an expander mandrel.
* This .002″ tension is what we have observed with Lapua 6mmBR, 6.5×47, 6.5 Creedmoor, and .308 Win brass. This might vary with much smaller or larger cases, and of course a different brand of brass might yield different results. If you get too little tension with your current mandrel, you can get a smaller-diameter mandrel from 21st Century Shooting. 21st Century even offers low-friction Titanium Nitride-coated mandrels.
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K&M Precision Shooting Products has two very handy products you may not know about yet. The first, a brilliantly simple device that lets you see your case necks as you expand them, can be used by anyone who necks-up brass (with a compatible expander die body). The second new product is a specialized “fat grip” holder that will make neck-turning easier for those of you out there who use K&M neck-turners.
K&M Expand Mandrel Window Riser
This is a simple threaded extension placed between your expander die body (K&M Expand Iron) and the top of your press. It carries the expander mandrel higher, above the press, and has a cut-out view port so you can see the mandrel as it passes through the neck. Smart, eh? This provides visual feedback during the process of expanding your brass. The patent-pending view riser costs $20.00. Will it expand necks faster, or reduce run-out? We doubt it, but we still would like to have one, if only to eyeball the mandrel to control the neck-entry rate more consistently from case to case.
Installation: Thread the Expand Mandrel Window Riser into the top of your loading press, then thread the K&M Expand-Iron (Expander Die Body) fully into the top of the window riser and adjust each so you can stroke out the press completely without driving the case mouth into the press adapter. This allows you to view the expanding operation which is typically blind under the press. The riser also eliminates the need for the stop screw in the expander mandrel. LINK: Expand Window Riser Instructions (PDF).
Ergo Holder for K&M Neck-Turning Tool
K&M’s rounded, oversized Ergo Holder lets you hold the K&M neck-turning body more securely (and with less hand cramping). Priced at $35.00, it is an expensive accessory, but we suspect many guys with K&M neck-turners will spring for an Ergo holder just because it gives you a more secure and comfortable grip on the small, square-edged K&M neck-turner.
Customer Feedback Inspired K&M’s Ergo Holder
The folks at K&M told us that their new Ergo Holder was produced in response to customer requests: “[Customers reported that] the neck turner can be hard to hold due to its compact size, especially in high-volume use. The Ergo Holder is machined from aluminum, providing a fatigue-proof grasp of the neck turner. Its mass works like a heat sink to help dissipate heat from the pilot during the turning process. The neck-turner body easily assembles into the Ergo Holder and is held in place with one set screw. The Ergo holder is also designed with the dial indicator in mind and actually makes its use more convenient”.
LINK: Ergo Holder Installation/Use Instructions (PDF).
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