Whose bushing dies- any differences?
- Thread starter tobnpr
- Start date
I doubt there's any difference between RCBS and Redding full bushing dies. Besides, their bushings are interchangeable. And they do indeed make very good resized cases.
But I do think a Forster full length sizing die with its neck honed out to the desired diameter (.002" smaller than that of a loaded round's neck) is a little better. Forster hones out their die necks for $12 each. It keeps the case neck perfectly aligned with the case shoulder (as well as the case body) as its sized down ending up with the case neck better centered on the case shoulder. RCBS and Redding's bushings have a few thousandths slop sideways in the bushing chamber; they're smaller in diameter than the chamber. And they don't size the case neck all the way to the shoulder but stop short about 1/32 inch. A resized case neck that's not centered on a case shoulder will be off center in the chamber neck on cases headspacing on their shoulder.
The difference is small. What gripes me the most is Redding (and probably RCBS, too) claims that unsized portion of the case neck better centers it in the chamber neck. Which is a fallacy because its diameter is smaller than the chamber neck. When the case shoulder centers in the chamber chamber shoulder from firing pin impact, that's what positions the case neck in the chamber neck when the round's fired.
But I do think a Forster full length sizing die with its neck honed out to the desired diameter (.002" smaller than that of a loaded round's neck) is a little better. Forster hones out their die necks for $12 each. It keeps the case neck perfectly aligned with the case shoulder (as well as the case body) as its sized down ending up with the case neck better centered on the case shoulder. RCBS and Redding's bushings have a few thousandths slop sideways in the bushing chamber; they're smaller in diameter than the chamber. And they don't size the case neck all the way to the shoulder but stop short about 1/32 inch. A resized case neck that's not centered on a case shoulder will be off center in the chamber neck on cases headspacing on their shoulder.
The difference is small. What gripes me the most is Redding (and probably RCBS, too) claims that unsized portion of the case neck better centers it in the chamber neck. Which is a fallacy because its diameter is smaller than the chamber neck. When the case shoulder centers in the chamber chamber shoulder from firing pin impact, that's what positions the case neck in the chamber neck when the round's fired.
stubbicatt
New member
Reportedly the Whidden dies are dimensioned for use on chambers cut by PT&G reamers. I bought a set for my 6.5x47 Lapua from Whidden, as the gunsmith used a PT&G reamer on my rifle, and they are very nice and do a good job.
I used Whidden dies on my 308 chambered CZ 550. I suspect they must be dimensioned closely for what would be a small base die or equivalent, as I experienced a need for much greater force to resize my CZ brass in the Whidden bushing dies than I did for standard RCBS or Hornady dies sizing the same cases.
If a factory chamber, based on my limited experience, I think I would choose Redding. Perhaps they won't require as much force to resize your brass.
I used Whidden dies on my 308 chambered CZ 550. I suspect they must be dimensioned closely for what would be a small base die or equivalent, as I experienced a need for much greater force to resize my CZ brass in the Whidden bushing dies than I did for standard RCBS or Hornady dies sizing the same cases.
If a factory chamber, based on my limited experience, I think I would choose Redding. Perhaps they won't require as much force to resize your brass.
I appreciate your effort but I am wondering why we make the effort, Bart B. claims it is only necessary for the case to fit the chamber like a peanut with hull in a punch bowl of violin case, and he has Sierra's support.
I continue to say I have a problem with that, it is not possible to have it both ways. If I neck size a fired case the case body fits the chamber, if I use a full length sizing die to neck size I only partially size the neck, the unsized portion of the neck fits the neck of the chamber and is as good as it gets. The case fits the chamber body, the case has minimum case clearance between the bolt face and case head and if the case outruns the firing pin there is minimum case travel. And, that is want I want, I want to cut down on all that case travel.
F. Guffey
Again, Guffey, you've misquoted me. I never said that. Sierra's tech made a similar one, but not what you said.
I think you've got the wherewithal to measure cases, rifle parts and chambers to learn that partial full length sizing of bottleneck cases is not as good as it gets. If it was, it would be popular amongst those getting best accuracy. It's not popular at all as been proved for decades. More often than not, it ends up making case headspace a thousandth or more longer than chamber headspace; the bolt binds when closing on the chambered round. A well-known cause of reduced accuracy.
And everyone except you knows a case cannot outrun a firing pin. Where do think the motive force is that could possibly make a chambered round move forward in the chamber by itself?
---------------------
243winxb, have you measured your .243's chamber neck diameter and compared that to what a case neck diameter is? Or are you just assuming the case neck's the same diameter as the chamber neck?
I think you've got the wherewithal to measure cases, rifle parts and chambers to learn that partial full length sizing of bottleneck cases is not as good as it gets. If it was, it would be popular amongst those getting best accuracy. It's not popular at all as been proved for decades. More often than not, it ends up making case headspace a thousandth or more longer than chamber headspace; the bolt binds when closing on the chambered round. A well-known cause of reduced accuracy.
And everyone except you knows a case cannot outrun a firing pin. Where do think the motive force is that could possibly make a chambered round move forward in the chamber by itself?
---------------------
243winxb, have you measured your .243's chamber neck diameter and compared that to what a case neck diameter is? Or are you just assuming the case neck's the same diameter as the chamber neck?
Last edited:
603Country
New member
Partial resizing will not, in every instance, move the case shoulder forward. It will do that to a case with little taper, but some tapered cases (220 Swift and 270, for instance) will allow some of the neck to be resized without that happening. I had excellent results for years with partial resizing for my 220. Granted that it was excellent results by my standards, which was very nice and very small groups. Probably though, the serious shooters might not have been happy with that. Still, I had many 5 shot groups that could hide under a dime.
I didn't get happy results partial resizing with 260 or 308 cases, or with 223 cases. The shoulder did move forward. That was corrected by partial resizing to the degree that the shoulder is bumped back. You can make a case (no pun intended) that the shoulder bump is, in fact, a form of partial resizing, though the purists will argue against using that terminology and will call it FL sizing or 'partial' FL sizing. Anyway, if you have a tapered case like that of the 30-06 family, try a partial resizing of some cases, to where the case neck has been sized for 2/3 of its length. Can't hurt to try it.
I didn't get happy results partial resizing with 260 or 308 cases, or with 223 cases. The shoulder did move forward. That was corrected by partial resizing to the degree that the shoulder is bumped back. You can make a case (no pun intended) that the shoulder bump is, in fact, a form of partial resizing, though the purists will argue against using that terminology and will call it FL sizing or 'partial' FL sizing. Anyway, if you have a tapered case like that of the 30-06 family, try a partial resizing of some cases, to where the case neck has been sized for 2/3 of its length. Can't hurt to try it.
My tests years ago with different cartridges and full length sizing dies learning which ones would move a fired case shoulder forward some amount with partial neck sizing all had the same thing happen. If a fired case was dropped into a sizing die and its head stuck out the bottom more than case neck length plus .125" shell holder height, its shoulder was pushed forward as the case body began to size down; sometimes before the case neck was starting into the die's neck. Cartridges used were 8x57 Mauser.30-06, .30-338 Mag, .270 Win., 7x57 Mauser, .264 Win Mag, .308 Win, .243 Win. All fired cases dropped into the sizing die stopping with their mouths short of touching the die's neck sizing chamber
Until the die's neck-shoulder juncture got back on case necks to just touching the shoulder, all had their shoulders moved forward. Only after the die's were lowered in the press a bit more did the case shoulders start moving back to or just past their fired position relative to the case head.
Any use of a full length sizing die that moves the shoulder back is typically meant to be full length sizing; not partial. Partial implies some part of the fired case from pressure ring to mouth is not touched by the sizing die. Full length sizing's when the total area from pressure ring forward to the case mouth is touched by the sizing die; doesn't matter how much the shoulder's set back.
There are some who insist that full length sizing is only done when the sizing die's set to have the shell holder stop against its bottom and the fired case is minimally sized to the limits of the die. If the shellholder stops as little as .001" before touching the bottom of the die, that's claimed to be partial full length sizing.
Until the die's neck-shoulder juncture got back on case necks to just touching the shoulder, all had their shoulders moved forward. Only after the die's were lowered in the press a bit more did the case shoulders start moving back to or just past their fired position relative to the case head.
Any use of a full length sizing die that moves the shoulder back is typically meant to be full length sizing; not partial. Partial implies some part of the fired case from pressure ring to mouth is not touched by the sizing die. Full length sizing's when the total area from pressure ring forward to the case mouth is touched by the sizing die; doesn't matter how much the shoulder's set back.
There are some who insist that full length sizing is only done when the sizing die's set to have the shell holder stop against its bottom and the fired case is minimally sized to the limits of the die. If the shellholder stops as little as .001" before touching the bottom of the die, that's claimed to be partial full length sizing.
Last edited:
603Country
New member
Bart, we're pretty much on the same page on all of this. I'd argue a bit further on the partial resizing and I'd have a go with my 220, but the new barrel has such a snug chamber that I have to FL size the cases these days.
Anyway, partial resizing has been around for an awful long time and even if it isn't today's chosen sizing technique for the serious competition shooters, most folks and their rifles might not even see a diff in accuracy. So I say to folks that they might want to try it and just see. Can't hurt. Both Nosler and Lyman have info on how to partial resize, so it isn't a technique to be spat upon.
Anyway, partial resizing has been around for an awful long time and even if it isn't today's chosen sizing technique for the serious competition shooters, most folks and their rifles might not even see a diff in accuracy. So I say to folks that they might want to try it and just see. Can't hurt. Both Nosler and Lyman have info on how to partial resize, so it isn't a technique to be spat upon.
I had a half dozen ways to size a 223 case, but for years and 7,000 rounds I used a Redding FL "S" die. It was the most expensive and the best looking.
Then I did a controlled experiment. Designing things and experiments is something I did for a living for many years, but someone else did the work. In my 223 experiment, I had to do all the work.
I randomly picked sets 25 cases and dedicate each set to one die.
I fired the cases over and over and measured two things:
1) case length growth
2) concentricity at the bullet ogive relative to rolling on the base of the case and rolling in the middle of the case shoulder. I had become convinced by Bart that the firing pin pushes the case forward and the shoulder taper centers in the chamber shoulder taper. I knew that the cartridge would be concentric at the shoulder, but checking for bent necks I thought the ogive where it will first touch the lands is test I want to do.
The Redding FL "S" die turned out to be the worst.
There were all the other dies.
The Lee collet neck die [that had been collecting dust for years] was the best.
Bart also convinced me that the shoulder centering does not work well with just neck sizing.
So I buy a FL die from Forster and have them hone out the neck to my specifications on one of their Hardinge collet lathes. This is how I push the shoulder back 0.001".
I think that the internet is full of pictures of good groups with "S" dies with tight neck chambers and brass with turned necks. But with a SAAMI chamber and unturned brass, the "S" die is poison... for me. Never again.
Then I did a controlled experiment. Designing things and experiments is something I did for a living for many years, but someone else did the work. In my 223 experiment, I had to do all the work.
I randomly picked sets 25 cases and dedicate each set to one die.
I fired the cases over and over and measured two things:
1) case length growth
2) concentricity at the bullet ogive relative to rolling on the base of the case and rolling in the middle of the case shoulder. I had become convinced by Bart that the firing pin pushes the case forward and the shoulder taper centers in the chamber shoulder taper. I knew that the cartridge would be concentric at the shoulder, but checking for bent necks I thought the ogive where it will first touch the lands is test I want to do.
The Redding FL "S" die turned out to be the worst.
There were all the other dies.
The Lee collet neck die [that had been collecting dust for years] was the best.
Bart also convinced me that the shoulder centering does not work well with just neck sizing.
So I buy a FL die from Forster and have them hone out the neck to my specifications on one of their Hardinge collet lathes. This is how I push the shoulder back 0.001".
I think that the internet is full of pictures of good groups with "S" dies with tight neck chambers and brass with turned necks. But with a SAAMI chamber and unturned brass, the "S" die is poison... for me. Never again.
603Country
New member
Interesting observations, Clark. I did a similar test with my 223, and after much shooting I decided that the Lee Collet Die and the Redding Type S FL die were pretty close on accuracy. That lasted till I reloaded some non neck-turned brass and found that I had the wrong size bushings, unless I turned the necks on all the new Lapua cases. So now I use the Lee Collet dies for most calibers. It doesn't care what our case neck wall thickness is. I now use the Redding bushing die, without the bushing, as a body die to bump shoulders as needed.
I've pretty much quit doing any partial resizing, now that I have Collet Dies. And...I have to admit that the Collet Die gave me better accuracy than partial resizing did. But that was with the 223 case, and not with the tapered case of the 220.
If I get ambitious, I might compare Partial Sizing, Collet Die neck sizing, and FL sizing (for the shoulder bump) in my 270. Maybe. Probably not. Too much work and recoil.
I've pretty much quit doing any partial resizing, now that I have Collet Dies. And...I have to admit that the Collet Die gave me better accuracy than partial resizing did. But that was with the 223 case, and not with the tapered case of the 220.
If I get ambitious, I might compare Partial Sizing, Collet Die neck sizing, and FL sizing (for the shoulder bump) in my 270. Maybe. Probably not. Too much work and recoil.
Aren't these separate and distinct issues?
I've always thought bushing dies were meant to "deal" with a single issue- bullet tension. Getting into neck vs fl sizing is an age old discussion, but a separate one- I thought.
Isn't bringing variables like shoulder bump, centering in the chamber, etc. muddying the waters? Valid as these may be, I don't see how they relate to neck tension, and bushing dies?
I've always thought bushing dies were meant to "deal" with a single issue- bullet tension. Getting into neck vs fl sizing is an age old discussion, but a separate one- I thought.
Isn't bringing variables like shoulder bump, centering in the chamber, etc. muddying the waters? Valid as these may be, I don't see how they relate to neck tension, and bushing dies?
tobnpr, I think you're right.
Neck grip is one thing, neck centering in the chamber is another. And shoulder bumping a third one. I never thought of it that way; thanks for being a bright light in the darkness of reloading unknowns. They are separate issues all combining to put all shot bullets into the same hole or as close to that as possible if all are done the right way.
I also think all three issues are solved with a single, one piece die whose neck diameter is best for the neck grip on the bullets and case neck wall thickness used. If such a die reduces fired case body diameters and sets shoulders back only .001" and sizes the neck just enough to grip the bullet as desired, maximum case life will happen as well as best accuracy. I think this what the benchrest community learned not too long ago. Even if those dimensions are reduced .002" and have a tiny more spread, case life and accuracy is virtually the same as been proved by those getting best results for decades in high power rifle matches and Sierra Bullets' methods of resizing their fired cases to test their stuff in.
Neck grip is one thing, neck centering in the chamber is another. And shoulder bumping a third one. I never thought of it that way; thanks for being a bright light in the darkness of reloading unknowns. They are separate issues all combining to put all shot bullets into the same hole or as close to that as possible if all are done the right way.
I also think all three issues are solved with a single, one piece die whose neck diameter is best for the neck grip on the bullets and case neck wall thickness used. If such a die reduces fired case body diameters and sets shoulders back only .001" and sizes the neck just enough to grip the bullet as desired, maximum case life will happen as well as best accuracy. I think this what the benchrest community learned not too long ago. Even if those dimensions are reduced .002" and have a tiny more spread, case life and accuracy is virtually the same as been proved by those getting best results for decades in high power rifle matches and Sierra Bullets' methods of resizing their fired cases to test their stuff in.
Neck sizing with a Bushing Die.
tobnpr, Go to Reddings Tech Line & Tips. http://www.redding-reloading.com/tech-line-a-tips-faqs You will find good information there. As i said above
tobnpr, Go to Reddings Tech Line & Tips. http://www.redding-reloading.com/tech-line-a-tips-faqs You will find good information there. As i said above
The bushing adjustment has nothing to do with the head to datum sizing of the case body. The groups on target will give you the answer.
There's some contradicting info in Redding's FAQ page relative to what people do getting the best accuracy with their handloads.
One is a slight amount of binding of the bolt when chambering a loaded round is preferred by one of the contributors to Redding's FAQ's. That's opposite what benchresters learned neck only sizing cases then having to full length size them when accuracy degraded by case headspace being greater than chamber headspace which caused the bolt binding in the first place.
Another claim Redding makes is the unsized portion of fired case neck helps center it in the chamber neck when fired. Anyone competent with and having the tools to do so, can easily measure the chamber and case to see that such claims are false and based on illogical assumptions.
If you're partial sizing with a full length sizing die, use a good tool to measure fired case headspace before sizing then again after sizing. Remember the difference and its direction.
When the bolt binds any amount on chambering the round, it won't be in the same place for every shot. The spread's greater with bolts whose face ain't square with the chamber axis; their high points won't always be aligned the same from shot to shot. That changes the force axis on the bolt from the case head slamming into it. And that causes the barrel's whip axis direction to change from shot to shot. It doesn't take a super accurate rile to see the difference.
One is a slight amount of binding of the bolt when chambering a loaded round is preferred by one of the contributors to Redding's FAQ's. That's opposite what benchresters learned neck only sizing cases then having to full length size them when accuracy degraded by case headspace being greater than chamber headspace which caused the bolt binding in the first place.
Another claim Redding makes is the unsized portion of fired case neck helps center it in the chamber neck when fired. Anyone competent with and having the tools to do so, can easily measure the chamber and case to see that such claims are false and based on illogical assumptions.
If you're partial sizing with a full length sizing die, use a good tool to measure fired case headspace before sizing then again after sizing. Remember the difference and its direction.
When the bolt binds any amount on chambering the round, it won't be in the same place for every shot. The spread's greater with bolts whose face ain't square with the chamber axis; their high points won't always be aligned the same from shot to shot. That changes the force axis on the bolt from the case head slamming into it. And that causes the barrel's whip axis direction to change from shot to shot. It doesn't take a super accurate rile to see the difference.
Last edited:
If the case had head space
, to some everything has head space and every gage is a head space gage. Why ? a reloader working with threads on the die and press is capable of adjust the die off the shell holder with precision, all that is required is a transfer, standard tool like the feeler gage. Some choose to start over every morning, they wake up in a new world every day. Simply adjust the die off the shell holder with a feeler gage to prevent the die body making contact the case body.
Or purchase a neck sizing die, I have neck sizing dies, I do not use them but I have them JIC, as in just in case.
F. Guffey
Clark thinks the internet is full of pictures of good groups with "S" dies with tight neck chambers and brass with turned necks. But with a SAAMI chamber and unturned brass, the "S" die is poison... for him. Never again, says he.
In spite of all Sierra Bullets are tested for accuracy with Redding S full bushing dies for cases they're available for. no case prep at all (including no neck turning) and shot in SAAMI spec chambers (no tight necks for the most part) getting what's probably the best accuracy with them compared to anybody, Clark's comment is interesting.
Some users of S dies are doing something different than others.
But this is normal; more often than not, the details of setup and use that make the difference in using one specific reloading tool good for some, bad for others.
In spite of all Sierra Bullets are tested for accuracy with Redding S full bushing dies for cases they're available for. no case prep at all (including no neck turning) and shot in SAAMI spec chambers (no tight necks for the most part) getting what's probably the best accuracy with them compared to anybody, Clark's comment is interesting.
Some users of S dies are doing something different than others.
But this is normal; more often than not, the details of setup and use that make the difference in using one specific reloading tool good for some, bad for others.
stubbicatt
New member
Bart B. I appreciate all your input. However, when using a FL bushing die, the bushing does not typically size the bottom ⅓ or so of a case neck just above the shoulder/neck junction. From my way of seeing things, that portion of the neck just above the shoulder should be pretty close to chamber neck dimensions, or at least closer to the chamber neck dimension than would be a neck sized all the way to the shoulder using a standard FL die, or a FL die honed out to get the tension one wants. Having that unsized portion of the neck closer to chamber dimensions it seems to me that the bullet would be closer to centered in the bore at the moment of firing.
Again assuming a .001 or .002 shoulder setback is accomplished by the body portion of the sizing die, it stands to reason that the cartridge would be supported in the chamber by that portion of the unsized neck at one end, and the bolt on the other end, which would tend to center up the cartridge in the chamber pretty well before firing, the remainder of the cartridge sort of suspended between these two points of support, not exactly contacting any other portion of the chamber in between. I suppose everything becomes pretty plastic during the time the cartridge has been fired and has obdurated against the chamber, and perhaps there are dynamic forces which would throw things askew at that time, such as non uniform wall thicknesses "banana shaping" the case and tilting the neck one way or other some amount.
Assuming a soft seated bullet, and a bushing sized neck, wouldn't one get the bullet nearly perfectly centered in the bore at the moment of closing the bolt this way?
Have I missed something here? Thanks in advance.
Again assuming a .001 or .002 shoulder setback is accomplished by the body portion of the sizing die, it stands to reason that the cartridge would be supported in the chamber by that portion of the unsized neck at one end, and the bolt on the other end, which would tend to center up the cartridge in the chamber pretty well before firing, the remainder of the cartridge sort of suspended between these two points of support, not exactly contacting any other portion of the chamber in between. I suppose everything becomes pretty plastic during the time the cartridge has been fired and has obdurated against the chamber, and perhaps there are dynamic forces which would throw things askew at that time, such as non uniform wall thicknesses "banana shaping" the case and tilting the neck one way or other some amount.
Assuming a soft seated bullet, and a bushing sized neck, wouldn't one get the bullet nearly perfectly centered in the bore at the moment of closing the bolt this way?
Have I missed something here? Thanks in advance.
Last edited:
stubbicat, you ask good questions.
Here's what happens when a rimless bottleneck case is chambered then fired. Note that this all happens even if the case neck's only .001" smaller than chamber neck.
First, when the bolt's closed on one, the extractor at the back end pushes the case head opposite its contact point on the rim/extractor-groove point. The case head stop against the flange on the bolt head or chamber wall at that point; depending on the dimensions and alignment of each. Typically, the case head's off center relative to the bore-chamber axis at this time. Mauser style ejectors push the case head to one side. Winchester post '64 ejectors in the bottom bolt lug push the chambered round against the top of the chamber.
Second, part 1, if the ejector is a Mauser style, it's not touching the case at all and has no effect whatsoever on positioning the chambered round. The case front to back position could be anywhere in a range equal to head clearance; the difference between chamber headspace and case headspace. If the round's heavy enough to over come what the extractor's pushing it, it may well rest on the bottom of the chamber. Depending on the difference in case body and neck diameters relative to the chamber at those points, either one may be clear of the chamber at those points. The case axis will not be in line with the chamber/bore axis.
Second, part 2, if the ejector is in the bolt face parallel to the firing pin and is spring loaded, that pushes the case forward until it stops against something. Typically, it's the chamber shoulder that stops the case shoulder from going further forward. There's enough clearance from the bolt face to the extractor claw for the case rim to move back and forth a few thousandths. As the case shoulder's moved forward against the chamber shoulder, it centers there as its angle is the same as the shoulder. Doing so will raise the case body off the bottom of the chamber as the case shoulder well centers in the chamber shoulder. The case neck is fixed in position on the case shoulder. It moves with the case shoulder. If it's well centered on the case shoulder, it'll be well centered in the chamber neck at this point.
Third, part 1, the firing pin's released and moves forward at about 5 mph. It strikes the primer in the case head. That moves the case forward in the chamber until it stops against the chamber shoulder. As both case and chamber shoulder are at the same angles, the case shoulder is now well centered in the chamber shoulder. The case neck moves with the case shoulder and now is also centered in the chamber neck; if it was sized straight on the case shoulder in the first place. Like above, the case body moves up off the chamber bottom, but only if it just happened to be there to begin with. There's enough force to set the case shoulder back .001" or more depending on shoulder shape /area and firing pin strength.
Third, part 2, same firing pin speed and striking things happen as above, but the case is already full forward in the chamber from ejector spring forces putting it there. So it gets driven forward an extra .001" or more. And the case neck is centered in the chamber neck as above, too.
Fourth, the firing pin finally dents the primer cup then crushes the primer pellet against its anvil a few microseconds after the case being slammed into the chamber shoulder and the round fires.
Main thing to remember is with cases headspacing on their shoulders, the case neck gets centered in the chamber neck slightly before the round fires. Whatever misalignment it has to the case shoulder is what moves it off the chamber neck axis. If the case neck's only .001" smaller than the chamber neck and the chamber neck's .001" off center from the case shoulder axis, it'll be .001 inch off center in the chamber neck when the round fires.
Note also that the case body is clear of the chamber body all the way around except at its back end at its pressure ring where it's pushed aside by the extractor. As there's no such thing as perfectly round cases and chambers, it helps to keep the case body diameter a thousandth or more smaller than that of the chamber. If there's not enough clearance for those variables to not have a case positioning issue, then accuracy suffers.
Here's what happens when a rimless bottleneck case is chambered then fired. Note that this all happens even if the case neck's only .001" smaller than chamber neck.
First, when the bolt's closed on one, the extractor at the back end pushes the case head opposite its contact point on the rim/extractor-groove point. The case head stop against the flange on the bolt head or chamber wall at that point; depending on the dimensions and alignment of each. Typically, the case head's off center relative to the bore-chamber axis at this time. Mauser style ejectors push the case head to one side. Winchester post '64 ejectors in the bottom bolt lug push the chambered round against the top of the chamber.
Second, part 1, if the ejector is a Mauser style, it's not touching the case at all and has no effect whatsoever on positioning the chambered round. The case front to back position could be anywhere in a range equal to head clearance; the difference between chamber headspace and case headspace. If the round's heavy enough to over come what the extractor's pushing it, it may well rest on the bottom of the chamber. Depending on the difference in case body and neck diameters relative to the chamber at those points, either one may be clear of the chamber at those points. The case axis will not be in line with the chamber/bore axis.
Second, part 2, if the ejector is in the bolt face parallel to the firing pin and is spring loaded, that pushes the case forward until it stops against something. Typically, it's the chamber shoulder that stops the case shoulder from going further forward. There's enough clearance from the bolt face to the extractor claw for the case rim to move back and forth a few thousandths. As the case shoulder's moved forward against the chamber shoulder, it centers there as its angle is the same as the shoulder. Doing so will raise the case body off the bottom of the chamber as the case shoulder well centers in the chamber shoulder. The case neck is fixed in position on the case shoulder. It moves with the case shoulder. If it's well centered on the case shoulder, it'll be well centered in the chamber neck at this point.
Third, part 1, the firing pin's released and moves forward at about 5 mph. It strikes the primer in the case head. That moves the case forward in the chamber until it stops against the chamber shoulder. As both case and chamber shoulder are at the same angles, the case shoulder is now well centered in the chamber shoulder. The case neck moves with the case shoulder and now is also centered in the chamber neck; if it was sized straight on the case shoulder in the first place. Like above, the case body moves up off the chamber bottom, but only if it just happened to be there to begin with. There's enough force to set the case shoulder back .001" or more depending on shoulder shape /area and firing pin strength.
Third, part 2, same firing pin speed and striking things happen as above, but the case is already full forward in the chamber from ejector spring forces putting it there. So it gets driven forward an extra .001" or more. And the case neck is centered in the chamber neck as above, too.
Fourth, the firing pin finally dents the primer cup then crushes the primer pellet against its anvil a few microseconds after the case being slammed into the chamber shoulder and the round fires.
Main thing to remember is with cases headspacing on their shoulders, the case neck gets centered in the chamber neck slightly before the round fires. Whatever misalignment it has to the case shoulder is what moves it off the chamber neck axis. If the case neck's only .001" smaller than the chamber neck and the chamber neck's .001" off center from the case shoulder axis, it'll be .001 inch off center in the chamber neck when the round fires.
Note also that the case body is clear of the chamber body all the way around except at its back end at its pressure ring where it's pushed aside by the extractor. As there's no such thing as perfectly round cases and chambers, it helps to keep the case body diameter a thousandth or more smaller than that of the chamber. If there's not enough clearance for those variables to not have a case positioning issue, then accuracy suffers.
Last edited:
Interesting discussion, and I need to ponder it...but for now a simple question (If there is such a thing here 
)
I was just getting ready to add the Redding Type S bushing die set and shellplate to my weekly Brownell's order- when it occurred to me that I can't order the bushings yet, right? Forgive the stupid question but just checking- I need to run at least a handful of the new brass through the die first, then measure for bushing size(s) needed, correctamundo?
)I was just getting ready to add the Redding Type S bushing die set and shellplate to my weekly Brownell's order- when it occurred to me that I can't order the bushings yet, right? Forgive the stupid question but just checking- I need to run at least a handful of the new brass through the die first, then measure for bushing size(s) needed, correctamundo?