Size inside or outside of neck as last step?

Western Living

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Sep 27, 2020
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I reload a couple different 6.5mm cartridges. At the moment, I'm working on my tools for 6.5 Grendel which I use in a bolt-action rifle. I use Starline brass.

First of all, I full-length size the cases every time with a Redding body die. I have it adjusted to bump the shoulder a couple thou according to a Sinclair comparator tool.

To size the necks, my die set came with a Redding Type S bushing neck die. To get the correct size bushing, I measured a fired case and compared it to a loaded one, thus taking into consideration the thickness of the Starline brass.

Fired case OD: 0.300"
Loaded case OD: 0.288"

I started with a 0.290" bushing with no expanding button and the cases came out 0.288". Redding documentation indicates this will happen when sizing the necks down more than ten thou in a single step -- the neck will come out smaller than the bushing size. It's also indicated to cause issues with concentricity, but I have not measured that.

With an OD of 0.288", I had basically zero neck tension and my seated bullets would sometimes push into the cases with finger pressure. I bought another bushing, knowing the cases would come out of it smaller than specified. So I bought a 288 bushing. Sometimes the cases will come out of it at 286, but sometimes they will come out at 287 or 288.

I started annealing all my necks every time. Although I think it is good practice, it still does not resolve the inconsistency when sizing down more than 10 thou with a single neck bushing.

Previously, I had not been using the expanding button at all. When I bought the smaller bushing, I got the carbide button but did not use it. Even if I had it installed, it would not touch the brass. The original button and the carbide button are 0.262" and my Starline brass would have to have an OD of 285 for the button to touch the inside of the neck. It would need to have an OD of 284 for the button to actually move the brass a thou.

Apparently, I needed a still smaller bushing, maybe a 286, but I could not expect the results to be consistent unless I also bought a 292 to bring the size down in steps smaller than ten thou.

At the time, 286 was out of stock and I was frustrated, so I bought a Lee Collet Die instead and used it to smash the necks onto the mandrel and get a 286 OD, two-thou under a loaded cartridge.

It's been about a year now and I'm loading for this rifle again and looking to do it better as ever.

Should I get a Redding 292 and 286 bushing and bring it down from 300 in two steps?
Should I use the LCD to bring it down under 290 with light pressure on the collet, and then finish it with a Redding 286 bushing?
Should I get a Redding 285 or 284 bushing and then use the carbide button to pull the neck back to an OD of 286 but from the inside instead of outside?
Should I use a Redding 285 or 286 bushing or the LCD to smash the neck down and then open it with a Sinclair, Wilson or K+M mandrel to an OD of 287?

Considering that I am not turning the OD of the neck, should I be forming the outside (bushing) or the inside (mandrel or button) as the last step?
 
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Western Living

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With what tool? Bushings?
Where do you stop? At the final OD before seating? Or below the final OD and then open it up with a mandrel?
 
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straightshooter1

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I reload a couple different 6.5mm cartridges. At the moment, I'm working on my tools for 6.5 Grendel which I use in a bolt-action rifle. I use Starline brass.

First of all, I full-length size the cases every time with a Redding body die. I have it adjusted to bump the shoulder a couple thou according to a Sinclair comparator tool.

To size the necks, my die set came with a Redding Type S bushing neck die. To get the correct size bushing, I measured a fired case and compared it to a loaded one, thus taking into consideration the thickness of the Starline brass.

Fired case OD: 0.300"
Loaded case OD: 0.288"

I started with a 0.290" bushing with no expanding button and the cases came out 0.288". Redding documentation indicates this will happen when sizing the necks down more than ten thou in a single step -- the neck will come out smaller than the bushing size. It's also indicated to cause issues with concentricity, but I have not measured that.

With an OD of 0.288", I had basically zero neck tension and my seated bullets would sometimes push into the cases with finger pressure. I bought another bushing, knowing the cases would come out of it smaller than specified. So I bought a 288 bushing. Sometimes the cases will come out of it at 286, but sometimes they will come out at 287 or 288.

I started annealing all my necks every time. Although I think it is good practice, it still does not resolve the inconsistency when sizing down more than 10 thou with a single neck bushing.

Previously, I had not been using the expanding button at all. When I bought the smaller bushing, I got the carbide button but did not use it. Even if I had it installed, it would not touch the brass. The original button and the carbide button are 0.262" and my Starline brass would have to have an OD of 285 for the button to touch the inside of the neck. It would need to have an OD of 284 for the button to actually move the brass a thou.

Apparently, I needed a still smaller bushing, maybe a 286, but I could not expect the results to be consistent unless I also bought a 292 to bring the size down in steps smaller than ten thou.

At the time, 286 was out of stock and I was frustrated, so I bought a Lee Collet Die instead and used it to smash the necks onto the mandrel and get a 286 OD, two-thou under a loaded cartridge.

It's been about a year now and I'm loading for this rifle again and looking to do it better as ever.

Should I get a Redding 292 and 286 bushing and bring it down from 300 in two steps?
Should I use the LCD to bring it down under 290 with light pressure on the collet, and then finish it with a Redding 286 bushing?
Should I get a Redding 285 or 284 bushing and then use the carbide button to pull the neck back to an OD of 286 but from the inside instead of outside?
Should I use a Redding 285 or 286 bushing or the LCD to smash the neck down and then open it with a Sinclair, Wilson or K+M mandrel to an OD of 287?

Considering that I am not turning the OD of the neck, should I be forming the outside (bushing) or the inside (mandrel or button) as the last step?
Sounds like your brass has pretty thin walled necks, like at ~.0125" thick. . . ???

If so, I'd use a .284 bushing. And I don't feel you really need to step it down. But, you should give it enough dwell time to get the brass time to completely form before starting to move the cases out of the die (like 5 or 6 seconds). Since you're annealing your brass, you shouldn't have much springback with enough dwell time.

Note, the neck wall thickness for any particular brass will determine which bushing you'll need to get the neck tension you want.
 
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Western Living

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Yes, the wall thickness at the neck is about 12 thou -- pretty average/typical for an AR-style cartridge, at least when I check 223 or 300BLK that's right where they're at also. Grendel is derived from 220 Russian and this neck wall thickness is also typical of that or other brass cases in that family like 6 PPC.

So if I were to use a .284 bushing, it would certainly get down to at least that OD. I can see how additional dwell time might possibly cause plastic deformation to set-in that would prevent "spring-back" to a larger OD, but I doubt that dwell time with a bushing will enlarge the case neck. With a 284 bushing, would you seat the bullet in whatever comes out of that or pull the expander button through it afterward or maybe a mandrel die?
 

straightshooter1

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Yes, the wall thickness at the neck is about 12 thou -- pretty average/typical for an AR-style cartridge, at least when I check 223 or 300BLK that's right where they're at also. Grendel is derived from 220 Russian and this neck wall thickness is also typical of that or other brass cases in that family like 6 PPC.

So if I were to use a .284 bushing, it would certainly get down to at least that OD. I can see how additional dwell time might possibly cause plastic deformation to set-in that would prevent "spring-back" to a larger OD, but I doubt that dwell time with a bushing will enlarge the case neck. With a 284 bushing, would you seat the bullet in whatever comes out of that or pull the expander button through it afterward or maybe a mandrel die?
I have a personal preference for using an expander mandrel instead of buttons in dies, as I'm after a uniform ID and lowest runout. If you're neck walls are at .012" that's .024 + .264 = .288 OD for a loaded round. If you're after .002" neck tension, you need a .286 OD for loading. To get there, a .284 bushing should get you down to almost that (a little more after springback). Then a expander mandrel of .262 diameter should give you that .286 (or close to it) for the .286 you're after, if that's the neck tension you're going for. It's all predicated on what your actual neck thicknesses are.
 
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Western Living

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That sounds right. My loaded rounds are 288.

So is it true that pushing a mandrel in results in more uniform ID and lower runout than pulling a button out?

Should I be after 2 thou neck tension? I've tried to get 1 thou but since my existing tools failed to be consistent to the thou, I had some rounds with zero thou. If I had tools to obtain consistency to the thou, how much tension should I be after?

I would need to start with that 284 bushing to get my necks small enough for an expander to do anything. Then supposing I get an expanding mandrel like Sinclair, Wilson, 21st Century, or K+M. Would I want to get a 262 mandrel for two thou tension and a finished OD of 286? Or get a 263, and finish with an OD of 287 and have 1 thou neck tension. Which is better?
 

Western Living

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One of the reasons an expanding mandrel may be worth it to me is because I have two other 6.5mm cartridge to load for. The bushings are probably specific to a cartridge because brass thickness varies. My magnum has much thicker brass in the necks. But the bullets are the same and the ID mandrels would be the same provided I wanted the same neck tension.
 
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Western Living

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The Redding carbide expander button/ball I already have is also applicable to any 6.5 cartridge, provided I'm using a die suitable for it. I've read speculation that runout will be worse with the button than with a mandrel, but I think I would have to actually measure this know. I do not have a runout/concentricity gauge. I admire the 21st Century gauge but I've been advised by experts that concentricity doesn't actually matter. The many hundreds of dollars for a fine instrument that gives accurate information that doesn't help me seems like a poor value.

If it is true that concentricity is not an important quality for accuracy, what does seem to be important and what I see a lot of bench-rest shooters making a great deal of effort about is consistency in neck tension.

Because my chambers are not reamed for turned necks and I don't turn necks, I can either size my imperfect necks from the inside or the outside or if I do both then one or the other will be the last step and this will determine whether my neck has a consistent OD or a consistent ID before I seat the bullet.

If I size the OD last, the imperfections in the neck will be pushed to the inside. But then I will seat a bullet and it will push them back to the outside.

If I size the ID last, the imperfections will be pushed to the outside. Then when I seat a bullet, will the neck have more consistent tension around the circumference of the bullet?
 
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straightshooter1

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That sounds right. My loaded rounds are 288.

So is it true that pushing a mandrel in results in more uniform ID and lower runout than pulling a button out?

Should I be after 2 thou neck tension? I've tried to get 1 thou but since my existing tools failed to be consistent to the thou, I had some rounds with zero thou. If I had tools to obtain consistency to the thou, how much tension should I be after?
How much tension to go after really depends on what your particular gun likes. I would hesitate to go with .001 without having the necks turned as there could be enough variation in neck thickness to present a problem with some loads for the bullet staying seating where you want it due to recoil. There are some people who load with that little amount of tension and even some that are zero, but the latter are people who are loading long and jamming into the lands. You might find that .003 tension can give you better performance. You have to test them to find out.


I would need to start with that 284 bushing to get my necks small enough for an expander to do anything. Then supposing I get an expanding mandrel like Sinclair, Wilson, 21st Century, or K+M. Would I want to get a 262 mandrel for two thou tension and a finished OD of 286? Or get a 263, and finish with an OD of 287 and have 1 thou neck tension. Which is better?

As mention, the best way to tell which is better is to test each tension. After seating depths, neck tension can be the next best adjustment to get the most out of your loads.

The Redding carbide expander button/ball I already have is also applicable to any 6.5 cartridge, provided I'm using a die suitable for it. I've read speculation that runout will be worse with the button than with a mandrel, but I think I would have to actually measure this know. I do not have a runout/concentricity gauge. I admire the 21st Century gauge but I've been advised by experts that concentricity doesn't actually matter. The many hundreds of dollars for a fine instrument that gives accurate information that doesn't help me seems like a poor value.

If it is true that concentricity is not an important quality for accuracy, what does seem to be important and what I see a lot of bench-rest shooters making a great deal of effort about is consistency in neck tension.

Whether concentricity is important or not depends on how far you intend to shoot and just how much runout there actually might be. When there's more than .004 TIR, I often can see it on paper with my groups at short range (not much, but it's there). Certainly, if one is talking about a hunting gun, I don't see any point to making a point for low runouts.

Because my chambers are not reamed for turned necks and I don't turn necks, I can either size my imperfect necks from the inside or the outside or if I do both then one or the other will be the last step and this will determine whether my neck has a consistent OD or a consistent ID before I seat the bullet.

If I size the OD last, the imperfections in the neck will be pushed to the inside. But then I will seat a bullet and it will push them back to the outside.
My chambers are not reamed for turned neck either, but I still turn my necks as it's more or less a one time operation to get uniform neck thickness in order to get consistent neck tension/interference. I don't want to so many things to think about as to why I get that one flyer that I can't explain.

True, most of the neck thickness imperfection will be moved to the outside by using an expander mandrel, and does make neck turning less important. A bullet, particularly a copper jacketed one, doesn't do a very good job of distributing the expansion to get uniform interference. It's best to stick to an expander mandrel.


If I size the ID last, the imperfections will be pushed to the outside. Then when I seat a bullet, will the neck have more consistent tension around the circumference of the bullet?
Yes, and more consistent interference around the ID.
 
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rmfield

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I reload a couple different 6.5mm cartridges. At the moment, I'm working on my tools for 6.5 Grendel which I use in a bolt-action rifle. I use Starline brass.

First of all, I full-length size the cases every time with a Redding body die. I have it adjusted to bump the shoulder a couple thou according to a Sinclair comparator tool.

To size the necks, my die set came with a Redding Type S bushing neck die. To get the correct size bushing, I measured a fired case and compared it to a loaded one, thus taking into consideration the thickness of the Starline brass.

Fired case OD: 0.300"
Loaded case OD: 0.288"
Just an observation: Your fired case neck OD of .300" seems high and your loaded case neck OD seems low.

FWIW, my fired Starline .260 brass (once fired) runs about .294"-.295" out of a "no-neck-turn" chamber. The actual dimension at the chamber neck per my reamer drawing is .296". My loaded case necks measure .2926".

Neck turning probably explains the loaded case OD, but the .300" fired case OD is puzzling.
 
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acudaowner

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I have skipped all that removing extra steps in favor of closing the neck to a factory tightness with a die body don't need all the parts inside the die and no bushings then open the neck to what ever size I desire with expanding mandrels . as long as the brass will hold the bullet I want to go in it's closed enough when It sits on top without falling inside the case.
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best of luck how ever you decide to do your brass .
 

straightshooter1

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Just an observation: Your fired case neck OD of .300" seems high and your loaded case neck OD seems low.

FWIW, my fired Starline .260 brass (once fired) runs about .294"-.295" out of a "no-neck-turn" chamber. The actual dimension at the chamber neck per my reamer drawing is .296". My loaded case necks measure .2926".

Neck turning probably explains the loaded case OD, but the .300" fired case OD is puzzling.
I tend to agree in that .300 seems unusually high. My fired 6.5 PRC necks run at .297 out of a SAAMI spec chamber. As far as the loaded case neck OD, that's what you have when the neck wall thickness is at .012" . . . and I thought it might have been because the necks were turned; but I guess not. 🤷‍♂️
 
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Rhed

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Size outside. Then expand. I use 2 thou of neck tension. Bushing I use is 3 thou less then final. So that gives me about thou more to expand back. Just to iron things out and get it concentric. Works out great. Though recently I’ve been experimenting with a bushing of 4 thou less then expand back. Yielding better results. Your preference though. Btw, I do however anneal my brass before sizing workflow.
 

Western Living

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Yes. Thanks everybody.
I do anneal every time.
I don't turn necks.
0.300" is the spec for SAAMI Grendel chambers and that's what I have - no custom reamer, just factory CZ.
CIP, however, shows a spec of 7.44mm which is about 0.293". It looks like CZ followed SAAMI.

Considering how thin the brass is for this cartridge -- and it's not thinner than 223, 556, or other brass 7.62x39-derived cases -- they might have made the chamber spec tighter. 6.5x47, in contrast, has a tighter chamber at 7.4mm. Nevertheless, this is not a flaw with my Starline brass or the CZ rifle's chamber. They are what they're supposed to be.

So I'm considering that I ought to get a 284 bushing to really bring the neck diameter down and then push it open with a mandrel, and according to the ongoing mandrel thread, the black nitride mandrels from 21st Century might be the slickest thing at the moment.
 

338dude

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I reload a couple different 6.5mm cartridges. At the moment, I'm working on my tools for 6.5 Grendel which I use in a bolt-action rifle. I use Starline brass.

First of all, I full-length size the cases every time with a Redding body die. I have it adjusted to bump the shoulder a couple thou according to a Sinclair comparator tool.

To size the necks, my die set came with a Redding Type S bushing neck die. To get the correct size bushing, I measured a fired case and compared it to a loaded one, thus taking into consideration the thickness of the Starline brass.

Fired case OD: 0.300"
Loaded case OD: 0.288"

I started with a 0.290" bushing with no expanding button and the cases came out 0.288". Redding documentation indicates this will happen when sizing the necks down more than ten thou in a single step -- the neck will come out smaller than the bushing size. It's also indicated to cause issues with concentricity, but I have not measured that.

With an OD of 0.288", I had basically zero neck tension and my seated bullets would sometimes push into the cases with finger pressure. I bought another bushing, knowing the cases would come out of it smaller than specified. So I bought a 288 bushing. Sometimes the cases will come out of it at 286, but sometimes they will come out at 287 or 288.

I started annealing all my necks every time. Although I think it is good practice, it still does not resolve the inconsistency when sizing down more than 10 thou with a single neck bushing.

Previously, I had not been using the expanding button at all. When I bought the smaller bushing, I got the carbide button but did not use it. Even if I had it installed, it would not touch the brass. The original button and the carbide button are 0.262" and my Starline brass would have to have an OD of 285 for the button to touch the inside of the neck. It would need to have an OD of 284 for the button to actually move the brass a thou.

Apparently, I needed a still smaller bushing, maybe a 286, but I could not expect the results to be consistent unless I also bought a 292 to bring the size down in steps smaller than ten thou.

At the time, 286 was out of stock and I was frustrated, so I bought a Lee Collet Die instead and used it to smash the necks onto the mandrel and get a 286 OD, two-thou under a loaded cartridge.

It's been about a year now and I'm loading for this rifle again and looking to do it better as ever.

Should I get a Redding 292 and 286 bushing and bring it down from 300 in two steps?
Should I use the LCD to bring it down under 290 with light pressure on the collet, and then finish it with a Redding 286 bushing?
Should I get a Redding 285 or 284 bushing and then use the carbide button to pull the neck back to an OD of 286 but from the inside instead of outside?
Should I use a Redding 285 or 286 bushing or the LCD to smash the neck down and then open it with a Sinclair, Wilson or K+M mandrel to an OD of 287?

Considering that I am not turning the OD of the neck, should I be forming the outside (bushing) or the inside (mandrel or button) as the last step?
I use a mandrel as my last step