Help understanding neck thickness and bushing dies

screamrider

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As I get more and more OCD about this reloading business, I'm now considering switching from my Redding Deluxe Die to a Redding S type bushing die.

I've used both federal and norma brass in my 300 WSM, and plan to stick with norma going forward.

If I measure the neck OD of a once fired norma case I get a very consistent measurement of 0.3440 from 20 pieces of brass. This is fire-formed, no resizing.

For wall thickness (using standard calipers), I get a relatively consistent 0.0170.

After I FL resize with my Redding deluxe die, I get a neck OD of 0.3380

A loaded dummy round with 180 grain TTSX gives a neck OD of 0.3390

So this tells me I get 0.001 neck tension (0.3390 - 0.3380) using my Redding deluxe die.

I also see that during the resizing process I'm compressing the neck 0.006 of an inch (0.3440 - 0.3380).

According to the Redding website, I should get a bushing 0.001 less than my loaded round neck diameter, so that puts me at a 0.338 bushing.

Is it just a coincidence that the bushing I need (0.338) is the exact neck OD I get from my non-bushing redding die?

That being said, is it even worth upgrading to the bushing die? I think concentricity may be the only benefit since the brass will be worked the same, or am I missing something? Does the regular die compress the neck way below 0.338 and then the expander ball brings it back to 0.338?
 

FearNoWind

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With respect to "does the regular die compress the neck way below 0.338 and then the expander ball brings it back to 0.338" the short answer is yes; most probably. The only way you'll know that for a certainty is to remove the expander ball and measure the neck of the resized case - compare that with the figure you got when you measured it with the expander ball engaged. With that data you'll get a better idea of how much work hardening the FL die and sizing ball are exerting on the case necks.
I use a FL die without the expander ball. I size the necks .001 under the bullet diameter and then put some insurance into concentricity by using a mandrel to make sure there aren't any kinks in the neck.
IMO, you'd do well to find a good home for the FL die expander ball and start working with a bushing die (I like the Redding series) fitted into the tube just tight enough so you can hear a slight rattle when you shake the die.
 

screamrider

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With respect to "does the regular die compress the neck way below 0.338 and then the expander ball brings it back to 0.338" the short answer is yes; most probably. The only way you'll know that for a certainty is to remove the expander ball and measure the neck of the resized case - compare that with the figure you got when you measured it with the expander ball engaged. With that data you'll get a better idea of how much work hardening the FL die and sizing ball are exerting on the case necks.
I use a FL die without the expander ball. I size the necks .001 under the bullet diameter and then put some insurance into concentricity by using a mandrel to make sure there aren't any kinks in the neck.
IMO, you'd do well to find a good home for the FL die expander ball and start working with a bushing die (I like the Redding series) fitted into the tube just tight enough so you can hear a slight rattle when you shake the die.
Thanks for the clarification.

One more quick question. I see that the Redding Type S FL bushing die comes with an expander ball as well. Let's say I get the .338 bushing - then what role does the expander ball play? If it opens the case up anymore it will no longer be .338. I'm guessing this isn't how it works, but otherwise I'm having trouble picturing the role of the expander ball in a bushing FL die.

Sorry for the simple question, just trying to figure this all out.
 

AZShooter

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Some of the Redding S bushing dies come with two sizer balls. One small so it can still hold the decapping pin and clear the neck. The only use I can think of for a .308 sizer ball that comes with the S busing die set is to iron out any dented necks of new brass. If your doesn't come with a smaller sizer ball you can always grind one down so it clears.

Are you aware that you have posted two neck wall sizes? You said it was .017" yet a loaded round is .339" As you can see calipers don't work that well for measuring neck wall thickness.
Subtracting .339 minus .308= .039 divide by 2 and you get .0155" for neck wall thickness.


If you buy a .338" bushing order a .337" at the same time. .001" might be a bit light for a bolt action repeating hunting rifle, the ammo in the mag box could have the bullet moving due to recoil with such a light neck tension. Only way to know for sure is to leave a round in the mag box and fire 3 or 4 then measure it.

Another nice feature of the bushing die is if you are working up a load and end up pulling a bunch of ammo that didn't shoot well. The bushing die is fast at resizing the necks, don't need any lube.
 

screamrider

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Some of the Redding S bushing dies come with two sizer balls. One small so it can still hold the decapping pin and clear the neck. The only use I can think of for a .308 sizer ball that comes with the S busing die set is to iron out any dented necks of new brass. If your doesn't come with a smaller sizer ball you can always grind one down so it clears.

Are you aware that you have posted two neck wall sizes? You said it was .017" yet a loaded round is .339" As you can see calipers don't work that well for measuring neck wall thickness.
Subtracting .339 minus .308= .039 divide by 2 and you get .0155" for neck wall thickness.


If you buy a .338" bushing order a .337" at the same time. .001" might be a bit light for a bolt action repeating hunting rifle, the ammo in the mag box could have the bullet moving due to recoil with such a light neck tension. Only way to know for sure is to leave a round in the mag box and fire 3 or 4 then measure it.

Another nice feature of the bushing die is if you are working up a load and end up pulling a bunch of ammo that didn't shoot well. The bushing die is fast at resizing the necks, don't need any lube.
Great, thanks for clarifying!

Yes, I noticed the exact same thing about neck wall thickness. When I used the measured thickness of the walls [(wall thickness x 2) + .308 -.001) I was getting .341 or .342 for bushing size, which would clearly be way too big. I now see how normal calipers are insufficient for measuring neck wall thickness.

I measured a few more loaded rounds and I'm finding a min measurement of 0.3385. I think I may just go with the 0.337 bushing.

Again, really appreciate your help.
 

barefooter56

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Thanks for the clarification.

One more quick question. I see that the Redding Type S FL bushing die comes with an expander ball as well. Let's say I get the .338 bushing - then what role does the expander ball play? If it opens the case up anymore it will no longer be .338. I'm guessing this isn't how it works, but otherwise I'm having trouble picturing the role of the expander ball in a bushing FL die.

Sorry for the simple question, just trying to figure this all out.
screamrider,
+1 on what AZShooter said. But let me add a couple things. Use the die with the expander ball installed on new brass to remove dents, and expand the case neck up so it will contact the bushing. You can upgrade to a carbide expander ball if you wish. The TYPE-S dies use the same carbide ball kits as the STANDARD Redding dies. DO NOT GET THE CARBIDE BALL KIT FOR THE COMPETITION DIES. Redding bushings can have a .001-.0015 variance in inside diameter either way so watch for this if the bullet seems to seat with little or no effort ( bushing size err to large ID) OR with more effort that seems normal ( bushing size err to small). These can also be a function of neck wall thickness variations between manufacturers or lots of brass. You may also want to do a test to check if you want to leave the expander ball installed in the die. Take 2 fired cases and a concentricity gauge. Check case concentricity on the neck about in the middle of the case neck of first case and note. Run the case through the die with the expander ball installed. Ckeck concentricity the same way again and note. Then repeat with the expander ball removed on the second case. See which way gives you the best result and leave the die set up for fired brass in that configuration. If you want you can also use L.E.Wilson bushings in Redding TYPE-S and Competition dies. You will have to use a different formula to figure bushing size . For .002 neck tension get a bushing .003 under the measurement across the neck of a loaded round. For .003 neck tension .004 under and so on. Reason is that Wilson bushing IDs are truer to the marked size and to account for spring back of the case neck. The Wilson bushings are also a "funnel" type bushing where as the Reddings are a tubular style. The funnel part of the Wilson bushing is their to help with guiding the case neck and to leave the last 1/3 or so of the neck unsized to help center the case in the chamber. One last thing. Install the Redding bushings in the die with the numbers facing DOWN TWORD THE CARTRIDGE CASE. There may be a raised edge where the bushing size has been stamped that can cock the busing in the die as it contacts the stop and effect concentricity.
 

FearNoWind

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...One last thing. Install the Redding bushings in the die with the numbers facing DOWN TWORD THE CARTRIDGE CASE. There may be a raised edge where the bushing size has been stamped that can cock the busing in the die as it contacts the stop and effect concentricity.
Try running the bushings over a piece of 400 grit emery cloth on a flat surface before putting them into use. Any high spots show up clearly and a few passes over the emery cloth removes them nicely.
 

screamrider

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screamrider,
+1 on what AZShooter said. But let me add a couple things. Use the die with the expander ball installed on new brass to remove dents, and expand the case neck up so it will contact the bushing. You can upgrade to a carbide expander ball if you wish. The TYPE-S dies use the same carbide ball kits as the STANDARD Redding dies. DO NOT GET THE CARBIDE BALL KIT FOR THE COMPETITION DIES. Redding bushings can have a .001-.0015 variance in inside diameter either way so watch for this if the bullet seems to seat with little or no effort ( bushing size err to large ID) OR with more effort that seems normal ( bushing size err to small). These can also be a function of neck wall thickness variations between manufacturers or lots of brass. You may also want to do a test to check if you want to leave the expander ball installed in the die. Take 2 fired cases and a concentricity gauge. Check case concentricity on the neck about in the middle of the case neck of first case and note. Run the case through the die with the expander ball installed. Ckeck concentricity the same way again and note. Then repeat with the expander ball removed on the second case. See which way gives you the best result and leave the die set up for fired brass in that configuration. If you want you can also use L.E.Wilson bushings in Redding TYPE-S and Competition dies. You will have to use a different formula to figure bushing size . For .002 neck tension get a bushing .003 under the measurement across the neck of a loaded round. For .003 neck tension .004 under and so on. Reason is that Wilson bushing IDs are truer to the marked size and to account for spring back of the case neck. The Wilson bushings are also a "funnel" type bushing where as the Reddings are a tubular style. The funnel part of the Wilson bushing is their to help with guiding the case neck and to leave the last 1/3 or so of the neck unsized to help center the case in the chamber. One last thing. Install the Redding bushings in the die with the numbers facing DOWN TWORD THE CARTRIDGE CASE. There may be a raised edge where the bushing size has been stamped that can cock the busing in the die as it contacts the stop and effect concentricity.
Thanks for the great info, I will definitely give this a go.

Any recommendations on a concentricity gauge, I don't have one yet?
 

AZShooter

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Every so often I read something that I didn't know. Never bothered inspecting any Redding bushings for burrs or flaws that could cause runout. Thanks guys for mentioning it.

I knew from talking to Redding the dimension of the bushing is the same from the stamped or opposite side so I have been inserting them either way for years.
 

Mikecr

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The resulting sizing from a bushing is also a matter of amount in sizing in one step.
For example, it's known that greater than 5thou of bushing sizing causes more than predicted. This is due to angle of inward rolling continuing past bushing ID.
 

screamrider

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The resulting sizing from a bushing is also a matter of amount in sizing in one step.
For example, it's known that greater than 5thou of bushing sizing causes more than predicted. This is due to angle of inward rolling continuing past bushing ID.
I was wondering about this exact point. My fire formed brass is 0.344 neck OD, and with a 0.337 bushing I would be compressing 7 thousandths. I thought I read on the Redding site that problems typically occur past 8 thou (end up with a narrower OD than the bushing is supposed to create), but I'm glad you told me otherwise.

Should I get a 0.340 and 0.337, using the 0.340 to step down from 0.344 before going to my final 0.337?
 

FearNoWind

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It's VERY expensive but I've never seen one that outperforms this one:
New Wheel-Drive Concentricity Gauge within AccurateShooter.com

One that I like and that doesn't break the bank is:
http://www.sinclairintl.com/reloadi...s/sinclair-concentricity-gauge-prod37479.aspx

I've used the Hornady model that some guys use as a concentricity gauge and bullet straightener but when you straighten the bullet while it's part way into the neck you are putting lateral stress on the case neck which adversely affects the uniforming of neck tension so I don't like that one.
 

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