Forster bushing bump neck die?

Lonewolf74 said:
Mike can you explain this more to me? Are the dies you use custom so they only "squeeze the case body" or are the Redding body dies slightly bigger to not size the body much if at all?
Click to expand...
Lonewolf74 said:
Can the same be accomplished using a FL bushing die or even non bushing FL die by redding or Whidden?
Click to expand...
Results from any die are an abstract until applied to YOUR situation (your brass/chamber). Redding body dies are intended to size the entire case bodies, given SAAMI dimension/tolerances.
So, if your chamber is tighter like most of mine then a Redding body die won't be sizing the body. Squeezing maybe ~1/4 to 1/2thou, and not causing yielding(sizing). This is support as good as any.
If you want this with a larger chamber (SAAMI) then I recommend fire-forming to full fit of the chamber, and then beyond that pressure(intended/desired pressure) enough to cause popping extraction, and then sending this brass off with a custom die order. They'll make a die that sizes a body based on that brass, while your good brass bodies will not actually be sized at all with that die. That is, if the die maker is any good,, and don't tell them what you're doing.
At this point you have a bump die. You can add any feature for neck sizing. No matter what I'm compelled to recommend partial neck sizing, to keep donut area out of neck tension.
 
Mikecr said:
Results from any die are an abstract until applied to YOUR situation (your brass/chamber). Redding body dies are intended to size the entire case bodies, given SAAMI dimension/tolerances.
So, if your chamber is tighter like most of mine then a Redding body die won't be sizing the body. Squeezing maybe ~1/4 to 1/2thou, and not causing yielding(sizing). This is support as good as any.
If you want this with a larger chamber (SAAMI) then I recommend fire-forming to full fit of the chamber, and then beyond that pressure(intended/desired pressure) enough to cause popping extraction, and then sending this brass off with a custom die order. They'll make a die that sizes a body based on that brass, while your good brass bodies will not actually be sized at all with that die. That is, if the die maker is any good,, and don't tell them what you're doing.
At this point you have a bump die. You can add any feature for neck sizing. No matter what I'm compelled to recommend partial neck sizing, to keep donut area out of neck tension.
Click to expand...


If he doesn't turn his necks, he cannot have donuts - it is impossible.
 
Thanks again for the help guy's.

Mike you kinda lost me with don't tell the die maker what your doing. What do you mean by that?

Another question, is nosler brass for the 300 win mag made by norma? What I'm thinking about doing is sending some fired brass to forster to get a semi custom die (they'll match there closest reamer to your brass) from what I understand.

The next issue is I don't have any dies for the 300 so the best I could do is buy a box of nosler ammo and fire it so it would only be once fired brass (I'd measure and send the largest pieces thinking this would most closely represent my actual chamber). And I plan on using norma brass which I heard is who makes nosler's brass so that's why I ask. I don't know, maybe if you don't think I'll gain much over an off the shelf die doing that I should try something else? I'm just really trying to get the best setup I can from the get go instead of buying multiple dies and keep tinkering with stuff down the road.
 
What I meant is that telling a die maker that your sent brass is already oversize will defeat your effort for a bump die. The die maker would just go another 1-2thou smaller, making it a body die.

You can't go with bumping only for just any cartridge. Forget it with a 300wm.. The case design and area do not provide this as viable potential. You'll soon need body sizing anyway.
 
Mikecr said:
What I meant is that telling a die maker that your sent brass is already oversize will defeat your effort for a bump die. The die maker would just go another 1-2thou smaller, making it a body die.

You can't go with bumping only for just any cartridge. Forget it with a 300wm.. The case design and area do not provide this as viable potential. You'll soon need body sizing anyway.
Click to expand...

So your saying with the 300 win mag I can't set a FL die or get a custome made to just set the shoulder back .001 or so every time I size?
 
Below is from the Widden custom die website.

Bushing vs Non-Bushing Sizer Dies
Standard Reloading Dies – Whidden Gunworks

Quite often we hear the question "What is the difference between a bushing full length sizer die and a non-bushing full length sizer die and which is best?"

 Full length sizer dies can be broken down into two types. With no preference on either, these types include the bushing sizer die and the non-bushing sizer die.

 The bushing sizer die uses a bushing to aid in the sizing of the neck while the body of the die does the sizing of the case body. When sizing the case, the bushing of the die is pressed around the outside of the neck just after the expander ball of the die passes through the neck. As the neck enters the bushing the bushing applies a predetermined amount of tension on the neck. The amount of tension is determined by the size of bushing used. As this action is performed the inconsistencies of the case neck wall are forced to the inside of the neck. As the sizer die is removed from the case the bushing exits the case neck and the expander ball returns through the neck. The diameter of the expander ball will determine the neck tension. When this action occurs the inconsistencies of the case neck wall are forced back to the outside of the neck case. In our experience this allows for a more consistent neck tension when the case is loaded.

 Some shooters prefer using no expander ball with a bushing die. In this case the expander ball is replaced with a pin retainer. The pin retainer is used to retain the decapping pin and protects the stem of the die. It serves no function in sizing. When a bushing sizer die is used with no expander ball, neck sizing is done by the bushing itself. With this method the amount of neck tension is determined by the size of the bushing as it is the only and last area of the die to be in contact with the neck of the case.

 The non-bushing sizer die works basically like the bushing sizer die. However, the non-bushing sizer die uses an expander ball to size the neck of the case. The expander ball passes through the neck of the case and sets the amount of neck tension. The non-bushing die is designed to size the outside of the neck as the case enters the body of the die. In determining neck tension with the non-bushing sizer die, simply change the expander ball size to obtain the desired amount of tension.

 So now, which is best? We'll let you decide....

 The bushing sizer die allows more flexibility in the amount of neck sizing. This is beneficial when changing brands of brass, neck turning brass to achieve different wall thickness and experimenting with different neck tensions in loading. To ease case neck entry into the bushing, all bushings have a small radius on the inside edge. This radius doesn't allow the sizing of the case neck fully to the shoulder.

 The non-bushing sizer die typically yields more concentric ammo in our experience. It also fully sizes the case neck fully to the shoulder for smoother functioning. Neck tension can only be determined by changing expander balls with the non-bushing die.

 These two die types are not to be confused as being interchangeable. If a bushing die is used, a bushing must be used to ensure the case is properly aligned in the die. With a non-bushing die, a bushing cannot be used.

Y3IiYL5.jpg


I have both runout gauges below and prefer to full length resize. The Hornady gauge on the left holds the case like it would be in the chamber if full length resized. Meaning the main body of the case never touches the chamber walls. The case will be supported in the rear by the bolt face and by the bullet in the throat. And the only part of the case that touches the chamber is the case shoulder. And the ejector/firing pin is what pushes the case forward into contact with the chambers shoulder.

My point being here is why do we spin the case on the case body and check bullet runout on a full length resized case when the case body never touches the chamber walls.

The RCBS case mastering gauge on the right spins the case on the body of the case and in my opinion better suited for neck sized cases.

Bottom line, too much of what benchrest shooters do filters down to the average shooter with off the shelf factory rifles. And I belong to the the "rat turd in the violin case" fraternity. And out of all my dies I get the most neck runout with my Forster bushing bump die. And I get the least neck runout with my full length Forster benchrest dies with the high mounted floating expander.


ed6Mwd8.jpg

 
CatShooter said:
---------


"In Benchrest Sanctioned match competition, one has to fire rounds as rapidly as possible in order to get all 5 record rounds on the target in one condition"


L.H.S. – Apparently, you have wandered too far afield from your "safe space". This is "LongRangehunting.com"… not benchrestcentral.com.


What works for benchrest, often does not apply to other shooting endeavors.


----------


"If I remember correctly from your posts on Accurate Shooter, most of your experience lies in military rifles."


L.H.S. - You do NOT remember correctly – I have almost no interest in military rifles.


I shot competitive bench in the '70s and again in the late 90s, and then I left it because it had changed and did not interest me anymore. I still have my bench rifles.


---------


"I have used a Forster bump neck die and confirmed they do indeed change the case diameter at the body-shoulder junction."


L.H.S. – Well, actually, this is not true. You have NOT used a Forster Bump die, so you could NOT have determined or confirmed anything.


In the thread on Accurateshooter.com … (click the linkie)


Headspace Comparitor & Bumping | Page 2 | Shooters' Forum


… you stated the following:


"OK, my gut instincts tell me that the shoulder/ neck junction will bulge without any body support. Since I got rid of all my neck sizers, I took a PPC case and using a Sinclair 30A bump gauge insert and pushing it against the bottom of a die as a stop in a press and was able to (with some finesse) set the shoulder back 0.0015". The diameter at this transition increased by 0.0003" and there was a definite bulge at the junction when holding a straight edge along the case body when held up to a light. For Benchrest requirements this would be unacceptable. Apparently bump only dies work OK under less stringent demands."


You didn't have, or use, or test a Forster Bump die, you made the whole thing up, relying on your "Gut"…!


Well, I would propose that your gut does not know anything about Forster Bump dies (and maybe handloading in general) so maybe find another use for it.

------

"Benchresters transitioned from neck sizing to full length sizing over a decade ago when accuracy gunsmiths started specing resize reamers that very closely matched the chambering reamer."

"I am not limited to starting to mid pressure loads. To be competitive I have to load in the upper load tier. So neck sizing is not an option."

L.H.S. – I never FL sized my match cases, and obviously, not all bench rest shooters have gotten he word on this shift to FL dies.

Terry Brady just shot the new world record group (an amazing 0.860") at 600 yards, with cases that were neck sized only

Terry says...
"[…] … I simply neck-size using a Wilson bushing die. In fact, my 6BR match brass has NEVER been full-length sized after it was fire-formed. The brass that shot the record had six or seven firings on it."

Read it for your self.

World Record Sub-Inch 600-Yard 6BR

---------

Now, the sad part of this, L.H.S. is… when guys come to a site like and ask a question about hardware, tools, actions, etc, they hope for (and should get) advice from people who know what they are talking about – that have actually used the equipment that is being discussed – that have real experience with it…

… not guesses by people that have never even used it, and are just blowing smoke to see themselves on the page.

You do the members of this board, and the owners of this board, a huge disservice!

Badd badd, L.H.S.
Click to expand...
My post you referenced in Accurate Shooter was from several months ago. My mentor still had a bump neck in which he proved to me that without full body support, the neck will tend to collapse in the case and depending on the hardness of the brass it can be enough to cause problems.
That Terry Brady article is from 2005. A lot has been learned in Benchrest in 12 years.....and a whole lot more has changed since your BR days in the '90's.
How about I just retreat back to Accurate Shooter and let you and BigEd be this site reloading professors. Life is too short to be called a liar based on someone googling and publishing outdated information.
 
Bigedp51,
Well your post containing Mr. Thomas's statements concerning the false hoods and misconceptions concerning FL-sizing VS NK-sizing are totally opposite what I have read in multiple highly regarded reloading manuals and resources.

Now I'm not about to ask you or anyone else to explain to me and in the process re-educate me on how to as Mr. Thomas states is "proper FL-resizing of a piece of brass" so will you please share with me what you consider is the best reloading manual that will explain this to me, as I have been only neck sizing my brass for years because virtually every reloading manual I own ( and I own them from Lyman, Nosler, Sierra, Lee,Speer and several other lesser known sources that specialize in accurate reloading for HP rifles) I'm pretty sure most if not all recommend NK-sizing VS FL sizing for accuracy and longer brass life for bolt rifles.

Although I have 30+ years of reloading experience, I am strictly a manual reading reloader and I hope I have a reasonably good grasp of the mechanics that apply to and govern the physics of what enables or disables rifle accuracy, but as such I'm not an engineer. I understand the how and why of bedding a rifle action and the harmonics of barrel vibration and how both affect every rifles accuracy or lack there of, but only from a academic point of view at best of one who reads a great deal but not having actually benefited first hand experience of much of people far more immersed in in the technological aspects of reloading for hyper accuracy such as I assume you and others like you have.

My reloading to date has been limited to trying to stay MOA to 300 yards as that is the longest range I have access to unless I wish to travel over 150 miles from my home, which for the last decade has become near impossible due to work and family.

Thanks,
DYager/Art
 
Below is from German Salazar's "The Riflemans Journal" website which has closed down. It is also the first place I heard the expression "Fit the chamber like a rat turd in a violin case". This is because Mr. Salazar was friends with the late Jim Hull of Sierra bullets ballistic test lab and competitive shooter.

A question was asked about "Partial Neck Sizing" with a full length die. And Mr. Salazar is explaining the benefits of full length resizing.

Reloading: Partial Neck Sizing
by German A. Salazar
http://riflemansjournal.blogspot.com/2010/06/reloading-partial-neck-sizing.html

"Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway."

What Mr.Salazar is saying above is we do not live in a world where each cartridge case is perfectly made with uniform wall thickness. And when a case is fired the thin side of the case will expand more. When this happens the case warps and becomes egg shaped and also referred to as a warped banana shaped case.

And what Mr. Salizar is saying is that the full length resized case has "less" guiding effect with the bullet and the bore. Meaning the less than perfect warped fired cases when full length resized will give the bullet "wiggle room" to be self aligning with the axis of the bore.

Bottom line, the Late Jim Hull and Kevin Thomas of the Sierra ballistic test laboratory along with German Salazar were members of the "rat turd in the violin case" club and full length resized all their cartridge cases.

And at the Whidden custom die website they tell you they get the most concentric cases from non-bushing full length sizing dies.


NECO CONCENTRICITY, WALL THICKNESS AND RUNOUT GAUGE
NEWDIAL2.JPG



"Also referred to as "The Case Gauge," this item is designed to measure:

​
1) The curved "banana" shape of the cartridge case;
2) The relative wall thickness variation of a cartridge case;
3) The cartridge case head out-of-squareness;
4) Individual Bullets - out-of-round "egg shape" and/or
curved "banana" shape (excepting very small bullets);
5) The seated bullet and cartridge runout of loaded rounds. The accuracy of any firearm is determined -- and limited -- by the quality of the ammunition shot in it. The effect of imperfections in ammunition is cumulative; each flaw adds to the influence of all others. Precision shooters spend much time and effort "uniforming" cartridge cases, using advanced techniques to eliminate variation. Yet until recently, one of the most important of these variations has not been susceptible to detection by any device readily available to marksmen.

Normal manufacturing tolerances cause brass cartridge cases to vary in wall thickness around the circumference of their bodies. Under the stress of firing, a case with such variation stretches more readily along its thin side, transferring more pressure to the bolt face at that point and introducing an unbalanced force which contributes to bolt whip and vibration of the barreled action in its bedding. This whip and vibration varies from one shot to the next as cartridges are fired with their thin sides randomly oriented at different angles, causing reduced accuracy. The problem is made even worse if the brass is too hard or springy to completely fireform to the shape of the chamber, in which event the greater stretching of the case's thin side will cause it to develop a curve along the length of its body. These "banana" cases cannot hold a bullet aligned with and centered in the bore, undercutting the effectiveness of the handloader's careful case preparation."


 
Good morning Edwardus Maximus....

The problem with that gauge is that the rear of the case runs in the extraction groove, and that will show a non-concentricity error with 99.9% of fired cases, even when they are perfect.

When a case is fired, the body will swell to fill the chamber - and since the case is smaller than the chamber, and lies at the bottom of the chamber (by gravity) the case will bulge on top - and any observant reloader has seen this bulge.

The case can be sized with the best dies, and be perfect, but if you test the concentricity with this tool... and the rear (head) is running in the extractor groove, then the case will show wobble.

If you test the same case with any of the other gauges, like the Sinclair, or the RCBS, which supports the head end just in front to the web, it will run true, just the way it would sit in the chamber....


SINCLAIR INTERNATIONAL SINCLAIR CONCENTRICITY GAUGE | Sinclair Intl


bigedp51 said:
Below is from German Salazar's "The Riflemans Journal" website which has closed down. It is also the first place I heard the expression "Fit the chamber like a rat turd in a violin case". This is because Mr. Salazar was friends with the late Jim Hull of Sierra bullets ballistic test lab and competitive shooter.

A question was asked about "Partial Neck Sizing" with a full length die. And Mr. Salazar is explaining the benefits of full length resizing.

Reloading: Partial Neck Sizing
by German A. Salazar
http://riflemansjournal.blogspot.com/2010/06/reloading-partial-neck-sizing.html

"Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway."

What Mr.Salazar is saying above is we do not live in a world where each cartridge case is perfectly made with uniform wall thickness. And when a case is fired the thin side of the case will expand more. When this happens the case warps and becomes egg shaped and also referred to as a warped banana shaped case.

And what Mr. Salizar is saying is that the full length resized case has "less" guiding effect with the bullet and the bore. Meaning the less than perfect warped fired cases when full length resized will give the bullet "wiggle room" to be self aligning with the axis of the bore.

Bottom line, the Late Jim Hull and Kevin Thomas of the Sierra ballistic test laboratory along with German Salazar were members of the "rat turd in the violin case" club and full length resized all their cartridge cases.

And at the Whidden custom die website they tell you they get the most concentric cases from non-bushing full length sizing dies.


NECO CONCENTRICITY, WALL THICKNESS AND RUNOUT GAUGE
NEWDIAL2.JPG



"Also referred to as "The Case Gauge," this item is designed to measure:

​
1) The curved "banana" shape of the cartridge case;
2) The relative wall thickness variation of a cartridge case;
3) The cartridge case head out-of-squareness;
4) Individual Bullets - out-of-round "egg shape" and/or
curved "banana" shape (excepting very small bullets);
5) The seated bullet and cartridge runout of loaded rounds. The accuracy of any firearm is determined -- and limited -- by the quality of the ammunition shot in it. The effect of imperfections in ammunition is cumulative; each flaw adds to the influence of all others. Precision shooters spend much time and effort "uniforming" cartridge cases, using advanced techniques to eliminate variation. Yet until recently, one of the most important of these variations has not been susceptible to detection by any device readily available to marksmen.

Normal manufacturing tolerances cause brass cartridge cases to vary in wall thickness around the circumference of their bodies. Under the stress of firing, a case with such variation stretches more readily along its thin side, transferring more pressure to the bolt face at that point and introducing an unbalanced force which contributes to bolt whip and vibration of the barreled action in its bedding. This whip and vibration varies from one shot to the next as cartridges are fired with their thin sides randomly oriented at different angles, causing reduced accuracy. The problem is made even worse if the brass is too hard or springy to completely fireform to the shape of the chamber, in which event the greater stretching of the case's thin side will cause it to develop a curve along the length of its body. These "banana" cases cannot hold a bullet aligned with and centered in the bore, undercutting the effectiveness of the handloader's careful case preparation."
Click to expand...
 
CatShooter said:
Good morning Edwardus Maximus....

When a case is fired, the body will swell to fill the chamber - and since the case is smaller than the chamber, and lies at the bottom of the chamber (by gravity) the case will bulge on top - and any observant reloader has seen this bulge.
Click to expand...

Below is a No.4 Enfield bolt face and it lets the case lay in the bottom of the chamber because it does not support the rear of the case

IMGP6308a-1.jpg


Below is a Remington 700 "recessed" bolt face that supports and centers the rear of the case in the chamber. Meaning this type bolt face does not let the case lay in the bottom of the chamber. And as German Salazar stated minimizes "case droop" with the rear of the case having clearance between the case and chamber. And "WHY" a full length resized case body does not touch the chamber walls. The only part of a full length resized case that touches the chamber is the case shoulder.

IMG_8545.jpg


Reloading: Partial Neck Sizing
by German A. Salazar

"Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway."


A case expands more on the thin side of the case and this can be in any direction, meaning not just upward. And this is why I posted the NECO case gauge information below about warped cases.

"Normal manufacturing tolerances cause brass cartridge cases to vary in wall thickness around the circumference of their bodies. Under the stress of firing, a case with such variation stretches more readily along its thin side, transferring more pressure to the bolt face at that point and introducing an unbalanced force which contributes to bolt whip and vibration of the barreled action in its bedding"

The above isn't just my opinion it was written about by German Salazar and Kevin Thomas to name just the two who I referenced.

I full length resize my cases and belong to the case should fit the chamber like a "rat turd in a violin case" fraternity.
 
I'm starting to see that there is no cut and dry answer to this, only to test and experiment with things to see what what gives the best results for you and your setup. So I've decided to get both a FL and a neck sizing die and see for myself.

So what are your guy's thoughts on load development without burning up a ton of shots testing between FL and NS? Would you start work up with each charge then bullet seating depth for both FL and NS brass? Or should you be able to find a pet load for say FL sized brass then test that same load with NS brass? My gut tells me you need to test each variable between the two to find the very best load/seating combo.

Problem is if you wanna test a few different powders and bullets this can turn into a ton of shots, not that I mind shooting a lot I'd just rather more of it be real practice than load development!

Thanks again for your help
 
Below is a Remington 700 "recessed" bolt face that supports and centers the rear of the case in the chamber. Meaning this type bolt face does not let the case lay in the bottom of the chamber. And as German Salazar stated minimizes "case droop" with the rear of the case having clearance between the case and chamber. And "WHY" a full length resized case body does not touch the chamber walls. The only part of a full length resized case that touches the chamber is the case shoulder.
Click to expand...


IMG_8545.jpg


Reloading: Partial Neck Sizing
by German A. Salazar
Click to expand...
Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway.
Click to expand...


It is not true that a resized case has a maximum clearance of 0.001" - that might be the case with a custom bench rifle and custom dies(but that will cause a bunch of extraction problems with "clickers")...
... but with the average over the counter rifle, or custom hunting rifle, there can be a hellova lot of "air" in that space... there can be 10 thou (0.010" of clearance in a max SAAMI chamber, with a Min SAAMI case web.
I have NEVER seen a case with a body expansion that was uniform all around the base... plus, the Remington extractor exerts a sideways force on the resting cartridge, so it expands out to one side - but once that happens, the case will be a perfect fit to the chamber, (unless some dumb bunny FL sizes it) :) :) :)

One option that has not been discussed (IF run-out is a prime consideration), is the Redding Comp bushing neck sizer.

One does not see them too often because of their cost ($120-ish to $160-ish). I was, and still am, a user of Redding "S" bushing neck dies... and when I first saw the comp bushing neck sizer in the Redding catalogue, I thought, "Who the hell needs a micrometer on a neck sizer?"

But when I put together my 6mmBR bench rifle, I bought a Redding Competition die set - a Comp bushing neck sizer, comp seater, and body die (a big waste of space in the box). It was my first hands on exposure to the comp bushing neck sizer and WOW...
Is that comp bushing neck sizer die cool.

It uses a floating sleeve, and forces the case into alignment with the axis of the sleeve...
... then it then brings the bushing (which is locked in place on the same axis) down on the neck, which cannot move cuz it is locked in place.

The run-out on my .220 Swift cases, which have a large neck (10 thou over the loaded neck dia) is less than 0.001" ... in one pass !!

---

I full length resize my cases and belong to the case should fit the chamber like a "rat turd in a violin case" fraternity.
Click to expand...
And I neck size my cases and belong to the case should fit the chamber like "jello fits in the mold" fraternity. :) :) :)
 
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