Case Runout

stubbicatt · July 5, 2013, 01:03 PM

I'm at a loss here. I'm on the 3rd loading of Lapua 308 cases. First two loadings, I did not have a concentricity/runout gage. The runout gage is a 21st Century gage.

Loaded rounds from the second loading of these cases are all under .002" as measured on the bullets somewhere near the transition from the bearing surface to the ogive. Most are about .0015". The last reload was FL conventionally sized with RCBS X Die, and seated with a Lee seater die. OK, so far so good.

So, I took 10 2x fired cases, lubed 'em up, and ran them up into a Lee FL die w/o the neck expander. I then ran them over an expander mandrel to prepare them for neck turning, and then I thought to measure runout. These cases are showing well over .002 runout midway on the case neck, both before and after the neck turning procedure. Some are well over .003"!

I regret that I didn't measure the runout before sizing, and after withdrawing them from the Lee die and before employing the neck expander mandrel.

I am not sure which step in this process tilted the necks like that?

ETA: This bugged me so bad that I resized the cases after neck turning. I get average about 1 1/2 thousandths runout midway on the case neck. The runout is at about 1 thousandths before running the neck expander into the case. I probably should have lubed the case necks on the inside... I'll load these up and see where the bullets measure on runout. The case necks are quite consistent mic'ing at midway between 14 thou and 15 thou. Gotta love 21st Century lathe neck turner... zero measurable variation in case necks, all are at the same point on the tubing mic.

My initial thoughts are to get a bushing FL sizing die.

saitek · July 5, 2013, 09:53 PM

hi there one thing i found a couple years back is that allloading press's have a high side that it will normally thrust to .
take your concentricy gauge with one case ,find the high side then mark the case with a sharpie ,set the case back in the shell holder and rotate the shell a litte bit at a time and recheck with the gauge .
it may take a cou-ple time's rotating it but you should notice the run out dropping to the minimum you can get as you rotate the shell .
when it get's to the lowest amount put a mark on thet spot on thr press when it is lowered ,then you can mark the high spot's on the brass ,then you can index them in the press when you size .
this worked for me i was able to take l c brass with as muck runout as .012 an in a lot of them bring them down to .001 or .000 .

steve4102 · July 5, 2013, 11:05 PM

I gave up on checking "Neck" runout quite some time ago. The bullet is on the inside of the case neck not the outside. I do not care what the outside of the neck is doing, I care about what the inside of the neck is doing as this is what is going to affect "Bullet" runout. I only check "Bullet" runout.

In rifles that runout matters, I size a couple different ways.

One is to neck size with the Lee Collet Die, it makes very concentric ammo when measuring the bullet not the case neck. I then size the case body and bump the shoulders back with the Redding Body die.

Another is to size with the Forster FL sizing die with the expander removed. I then expand the necks with a Lyman "M" die. This too makes very concentric ammo when measuring the bullet not the neck.

stubbicatt · July 6, 2013, 08:15 AM

Two very thoughtful observations.

Steve4102, I understand your post, and it does make sense. My thinking is that if the neck is bent, so too will be the loaded rounds, as measured at the bullet. The neck turning did indeed create absolutely uniform neck walls, as measured by a ball micrometer, yet the necks seem to be bent a little bit, just under a thou to 1.5 thou.

I'll load these cases up after marking the high sides, and see if the seating operation improves matters.

Saitek, I didn't understand your posting so much I don't think. Not that you didn't say it well, but as I understood your posting, you suggest that the press will flex in a certain direction, and this flexing will induce case necks with greater runout? See, where I question this is, the case is fully supported within the die, which is doing the work, so relative to any point on the case itself, whether the press flexes or not, there would be no measurable runout due to this factor. If the neck only were in the die, and the press were flexing, the unsupported case body would bend according to the press flex.

I don't know if I expressed that very well, but I hope I did. Nonetheless, you got me thinking.

higgite · July 6, 2013, 08:52 AM

You didn't say what die you used with the expander mandrel. Is the case body supported in that die or is it free to "wobble" around inside the die?

My thought on bushing dies is same as Steve's, but since you turned the necks, that shouldn't be an issue.

stubbicatt · July 6, 2013, 09:50 AM

Good point Higgite. The neck expander mandrel is a simple die with no support for the case whatsoever, it just has that expander poking down.

This last time I resized and measured 10 cases, the most of them showed about .001" deflection before the inside expander mandrel, and around .0015" after having been expanded, so it did affect them. This does suggest that press deflection caused the runout to increase. Hm...

g.willikers · July 6, 2013, 10:00 AM

To add to the confusion, there's quite a few things to consider.
The fit of the bullet to the case.
The fit of the cartridge to the chamber.
The shape of the chamber.
The fit of the rim to the breech.
They all have to help provide a straight path for the bullet to enter the rifling.

Bart B. · July 7, 2013, 07:15 AM

The straightest bottleneck case necks I know of as they come out of a die are those full length sized in dies whose neck diameter is a couple thousandths smaller than that of a loaded round. And they size the fired case neck all the way back to the shoulder bumping that shoudler back a thousandth or two. No expander balls are used. The case body and shoulder is held in alignment with the case neck when sizing takes place.

Redding and RCBS company's full bushing dies do not size case necks all the way to the shoulder; they leave several thousandths of the neck in front of the shoulder unsized. Their reasoning is that this helps center the case neck in the chamber when its fired. But both company's are dead wrong in thinking and telling folks that unsized portion of the case neck helps center the neck in the chamber neck. It's the case shoulder that centers the front of the case in the chamber. The case neck floats free from contact with the chamber neck. It's too darned easy to measure the clearance and see what really happens, but neither company's ever done that as far as I know. But both company's dies are far better than conventional full length sizing dies with expander balls.

Benchresters finally switched from neck only sizing to full length sizing their fired cases. They use dies that size the body diameters down about one thousandth and the necks down just enough to hold the bullet tight enough for their use. Fired case shoulders are also set back a thousandth. But the case necks are sized all the way back to the shoulder so the sized case necks are best aligned on the case shoulder. Their necks, too, float free in the chamber neck.

Any up-sizing of a sized case neck after it's sized down will offset its center from the shoulder center. And this is what causes too much runout. It makes no difference whatsoever if the neck walls vary .001" in thickness. The center of such a case neck will only be off center in the chamber by half that amount anyway. Nobody I know can tell the difference of such offset of bullet to bore in calibers greater than 25. A few can with 22 and 24 caliber rounds. Seating bullets so they softly jam into the lands fixes this anhyway.

Most folks don't believe this.

July 5, 2013, 01:03 PM	#1
stubbicatt Senior Member Join Date: September 15, 2007 Posts: 1,707	Case Runout I'm at a loss here. I'm on the 3rd loading of Lapua 308 cases. First two loadings, I did not have a concentricity/runout gage. The runout gage is a 21st Century gage. Loaded rounds from the second loading of these cases are all under .002" as measured on the bullets somewhere near the transition from the bearing surface to the ogive. Most are about .0015". The last reload was FL conventionally sized with RCBS X Die, and seated with a Lee seater die. OK, so far so good. So, I took 10 2x fired cases, lubed 'em up, and ran them up into a Lee FL die w/o the neck expander. I then ran them over an expander mandrel to prepare them for neck turning, and then I thought to measure runout. These cases are showing well over .002 runout midway on the case neck, both before and after the neck turning procedure. Some are well over .003"! I regret that I didn't measure the runout before sizing, and after withdrawing them from the Lee die and before employing the neck expander mandrel. I am not sure which step in this process tilted the necks like that? ETA: This bugged me so bad that I resized the cases after neck turning. I get average about 1 1/2 thousandths runout midway on the case neck. The runout is at about 1 thousandths before running the neck expander into the case. I probably should have lubed the case necks on the inside... I'll load these up and see where the bullets measure on runout. The case necks are quite consistent mic'ing at midway between 14 thou and 15 thou. Gotta love 21st Century lathe neck turner... zero measurable variation in case necks, all are at the same point on the tubing mic. My initial thoughts are to get a bushing FL sizing die. Last edited by stubbicatt; July 5, 2013 at 07:29 PM.

July 5, 2013, 09:53 PM	#2
saitek Senior Member Join Date: October 30, 2011 Location: iowa Posts: 100	sizing straight hi there one thing i found a couple years back is that allloading press's have a high side that it will normally thrust to . take your concentricy gauge with one case ,find the high side then mark the case with a sharpie ,set the case back in the shell holder and rotate the shell a litte bit at a time and recheck with the gauge . it may take a cou-ple time's rotating it but you should notice the run out dropping to the minimum you can get as you rotate the shell . when it get's to the lowest amount put a mark on thet spot on thr press when it is lowered ,then you can mark the high spot's on the brass ,then you can index them in the press when you size . this worked for me i was able to take l c brass with as muck runout as .012 an in a lot of them bring them down to .001 or .000 .

July 6, 2013, 08:15 AM	#4
stubbicatt Senior Member Join Date: September 15, 2007 Posts: 1,707	Two very thoughtful observations. Steve4102, I understand your post, and it does make sense. My thinking is that if the neck is bent, so too will be the loaded rounds, as measured at the bullet. The neck turning did indeed create absolutely uniform neck walls, as measured by a ball micrometer, yet the necks seem to be bent a little bit, just under a thou to 1.5 thou. I'll load these cases up after marking the high sides, and see if the seating operation improves matters. Saitek, I didn't understand your posting so much I don't think. Not that you didn't say it well, but as I understood your posting, you suggest that the press will flex in a certain direction, and this flexing will induce case necks with greater runout? See, where I question this is, the case is fully supported within the die, which is doing the work, so relative to any point on the case itself, whether the press flexes or not, there would be no measurable runout due to this factor. If the neck only were in the die, and the press were flexing, the unsupported case body would bend according to the press flex. I don't know if I expressed that very well, but I hope I did. Nonetheless, you got me thinking. Last edited by stubbicatt; July 6, 2013 at 08:21 AM.

July 6, 2013, 10:00 AM	#7
g.willikers Senior Member Join Date: September 28, 2008 Posts: 10,442	To add to the confusion, there's quite a few things to consider. The fit of the bullet to the case. The fit of the cartridge to the chamber. The shape of the chamber. The fit of the rim to the breech. They all have to help provide a straight path for the bullet to enter the rifling. __________________ Walt Kelly, alias Pogo, sez: “Don't take life so serious, son, it ain't nohow permanent.”

July 5, 2013, 11:05 PM	#3
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,955	I gave up on checking "Neck" runout quite some time ago. The bullet is on the inside of the case neck not the outside. I do not care what the outside of the neck is doing, I care about what the inside of the neck is doing as this is what is going to affect "Bullet" runout. I only check "Bullet" runout. In rifles that runout matters, I size a couple different ways. One is to neck size with the Lee Collet Die, it makes very concentric ammo when measuring the bullet not the case neck. I then size the case body and bump the shoulders back with the Redding Body die. Another is to size with the Forster FL sizing die with the expander removed. I then expand the necks with a Lyman "M" die. This too makes very concentric ammo when measuring the bullet not the neck.

July 6, 2013, 08:52 AM	#5
higgite Senior Member Join Date: October 21, 2010 Posts: 1,025	You didn't say what die you used with the expander mandrel. Is the case body supported in that die or is it free to "wobble" around inside the die? My thought on bushing dies is same as Steve's, but since you turned the necks, that shouldn't be an issue.

July 6, 2013, 09:50 AM	#6
stubbicatt Senior Member Join Date: September 15, 2007 Posts: 1,707	Good point Higgite. The neck expander mandrel is a simple die with no support for the case whatsoever, it just has that expander poking down. This last time I resized and measured 10 cases, the most of them showed about .001" deflection before the inside expander mandrel, and around .0015" after having been expanded, so it did affect them. This does suggest that press deflection caused the runout to increase. Hm...

July 7, 2013, 07:15 AM	#8
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	The straightest bottleneck case necks I know of as they come out of a die are those full length sized in dies whose neck diameter is a couple thousandths smaller than that of a loaded round. And they size the fired case neck all the way back to the shoulder bumping that shoudler back a thousandth or two. No expander balls are used. The case body and shoulder is held in alignment with the case neck when sizing takes place. Redding and RCBS company's full bushing dies do not size case necks all the way to the shoulder; they leave several thousandths of the neck in front of the shoulder unsized. Their reasoning is that this helps center the case neck in the chamber when its fired. But both company's are dead wrong in thinking and telling folks that unsized portion of the case neck helps center the neck in the chamber neck. It's the case shoulder that centers the front of the case in the chamber. The case neck floats free from contact with the chamber neck. It's too darned easy to measure the clearance and see what really happens, but neither company's ever done that as far as I know. But both company's dies are far better than conventional full length sizing dies with expander balls. Benchresters finally switched from neck only sizing to full length sizing their fired cases. They use dies that size the body diameters down about one thousandth and the necks down just enough to hold the bullet tight enough for their use. Fired case shoulders are also set back a thousandth. But the case necks are sized all the way back to the shoulder so the sized case necks are best aligned on the case shoulder. Their necks, too, float free in the chamber neck. Any up-sizing of a sized case neck after it's sized down will offset its center from the shoulder center. And this is what causes too much runout. It makes no difference whatsoever if the neck walls vary .001" in thickness. The center of such a case neck will only be off center in the chamber by half that amount anyway. Nobody I know can tell the difference of such offset of bullet to bore in calibers greater than 25. A few can with 22 and 24 caliber rounds. Seating bullets so they softly jam into the lands fixes this anhyway. Most folks don't believe this.