hornady concentricity tool

I'm convinced the most common cause of crooked rifle bullets in reloaded cases is the sizing die's expander ball bending case necks as it's pulled out.

Resize 10 fired cases with an expander ball and 10 more without. Measure case neck run out at the mouth on them.
 
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A few comments

I have a few comments.

I use an RCBS hand operated neck turning tool and it's fine with me.

If my loads are not concentric, I make sure that wherever it's highest, I mark the casing and face all of the same cartridges in the same direction. Before turning the neck, I also mark which side of the neck was thickest

I once read that to reduce bullet runout that I would partially seat my bullet, then rotate the cartridge 60 degrees, seat the bullet further, turn the case another 60 degrees, and continue doing so until the bullet is completely seated. I took this as gospel but have never tested it to a bullet that was seated without rotating the brass. I just haven't tested it yet. Comments here?

Last, I haven't thought much about the scratches but if that's a problem, why not just use some Imperial Wax?
 
I doubt those scratched bullets pictured will cause accuracy problems. They're probably uniform all the way around. That ammo has to pass Federal accuracy tests.

Lubrication inside case necks won't stop the scratching. It's softer than brass therefore easily pushed aside.

Meanwhile, the details involved that give erroneous readings. Any runout in case body diameters where it rests on the gauge will be transferred to the dial indicator. Consider what happens to a cartridge whose bullet is perfectly aligned with the case axis.......

If the case body rear touch point (pressure ring?) is 2 inches back from the front point (next to the case shoulder?) and the indicator touch point on the bullet is 1 inch forward from the body touch point near the shoulder that has 0 runout, for every .002" runout on the rear touch point there's .001" runout on the bullet.

If the rear case touch point has 0 runout but there's .002" runout on the front case touch point, there's .003" runout on the bullet.

When the round is fired, the case shoulder is well centered in the chamber shoulder and the front touch point on the case body touches nothing. Only part of the case body that might be touching the chamber is the pressure ring.

Read post #15 in

https://thefiringline.com/forums/showthread.php?t=556622&highlight=dial+indicator+runout
 
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A run out tool is valuable in my experience. Sometimes a die can jam up weird in the threads and create excessive runout, IME. This can usually be fixed quite quickly.

The Hornady tool is no good, IMO. Let me explain. When looking at an object and taking data on it, the most important thing is that the part be held by the datum structure. Then the critical points are measured.

The Hornady holds the bullet tip. Not only is the tip not a datum point, but looking at bullet manufacturing, you will see it is where manufacturers put their variation. That will always create bad data.
 
Nathan,

Your comments about Hornady's runout gauge are valid, It'll give the lowest runout numbers for a given cartridge compared to those using two contact points on the case body.
 
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I picked up the 21st Century tool just to measure how capable my reloading process is.

I measured a maximum 0.0015" runout on the neck which didn't concern me much because that is the same amount of measured variation in case neck thickness. I don't turn necks (yet). I'm not convinced that will make me a better shooter.

Then I measured at approximately halfway between ogive and tip and found some really low numbers but some were higher than I'd like, 0.00425".

I removed the expander ball from the dies from the beginning and have always used​ bushings​ and expander mandrels so the expander ball isn't the cause. It almost has to be caused during the seating step but I can't completely eliminate it being caused at the neck sizing step. Both bushings and mandrels are able to free float within the dies.

I've always started the bullet, backed out, rotated the case 180° then finished seating. I think I would probably worry a lot less if I had never bought the tool, but I bought it because I wondered and felt compelled to know. Alright, now that I know what the problem is, figuring out the cure is the next step.
 
I'm a firm advocate of using only one piece dies to resize fired cases. Guarantees the neck is perfectly aligned with the case shoulder and body while their diameters are reduced. And only one process per case is needed.

Multiple piece dies have sizing parts that are not held in alignment during sizing.
 
Multiple piece dies have sizing parts that are not held in alignment during sizing.
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when using a bushing die you back off a quarter turn on the bushing adjustment to give free float to the bushing which will then align itself to the neck/body. The bushing will follow the path of least resistance, there is no lateral force being applied that would misalign the neck. On a bolt gun the neck and body will be perfectly aligned after firing and leaving the chamber, so a free floating bushing is the best chance of maintaining a straight case and neck. I can't say about gas operated rifles, never been able to get one to shoot precise enough to matter.
 
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hounddawg said:
when using a bushing die you back off a quarter turn on the bushing adjustment to give free float to the bushing which will then align itself to the neck/body. The bushing will follow the path of least resistance, there is no lateral force being applied that would misalign the neck. On a bolt gun the neck and body will be perfectly aligned after firing and leaving the chamber, so a free floating bushing is the best chance of maintaining a straight case and neck. I can't say about gas operated rifles, never been able to get one to shoot precise enough to matter.
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My tests on neck alignment in an actual chamber when the resized case is in the firing position show otherwise. The test chamber was one cut off the back end of a 7.62 NATO M1 Garand barrel.

Ditto when the resized case is measured for neck runout in a gauge whose front case reference is like that of the chamber.
 
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"I can’t load a concentric round if my life depended on it"

The following quote may be a hint.

"when using a bushing die you back off a quarter turn on the bushing adjustment to give free float to the bushing which will then align itself to the neck/body."
 
The test chamber was one cut off the back end of a 7.62 NATO M1 Garand barrel.
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well there ya go

seriously comparing even a good factory bolt gun of today to a Garrand is kind of like comparing the ride of a new F150 to a 1935 Ford. My brass never even hits the bench. The necks don't need to be wrestled into shape
 
seriously comparing even a good factory bolt gun of today to a Garrand is kind of like comparing the ride of a new F150 to a 1935 Ford. My brass never even hits the bench. The necks don't need to be wrestled into shape
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Based on his other posts, I’ll bet he means a modern SS match barrel chambered to excellent tolerances.
 
That chamber section came from a regular service grade barrel. None of the USN barrels were made to M14NM 7.62 NATO specs. Only air gauged for uniform groove diameters. 3077" to .3079" for use in match grade rifles. A couple thousandths spread in chamber diameters or headspace doesn't hinder any from chambering a given straight cartridge such that its neck is well centered in the chamber neck. Such barrels tested under 4" at 600 yards with new, unprepped primed cases using IMR4320 and Sierra 190 HPMK's.

If you cut off the top half of a Dixie cup then drop it in another cup, it'll center perfectly in the bottom of the uncut one. Even if their taper angle has a one degree difference. Same thing with chamber and cartridge shoulder angles.

A straight 243 Winchester, 260 Remington, 7-08 and 308 Winchester cartridge will perfectly center their bullets in a 358 Winchester chamber when fired.
 
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Based on his other posts, I’ll bet he means a modern SS match barrel chambered to excellent tolerances.
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If your case necks are crooked after being fired you probably need a new barrel more than a concentricity gage
 
hounddawg said:
If your case necks are crooked after being fired you probably need a new barrel more than a concentricity gage
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The only way a chamber neck can be crooked to the chamber body is the barrel's bent at that point.

There's no way a straight reamer can make just the neck crooked.
 
The only way a chamber neck can be crooked to the chamber body is the barrel's bent at that point.

There's no way a straight reamer can make just the neck crooked
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you were the one saying the necks were leaving the chamber crooked in a earlier post

The following quote may be a hint.

"when using a bushing die you back off a quarter turn on the bushing adjustment to give free float to the bushing which will then align itself to the neck/body."
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if you lock a bushing down tight it may be able to bend the neck to fit it. However if you give it a few thousands play the bushing's tapered entrance will allow the bushing to float into alignment with the neck. Since Bart has already established that the neck and the body will be in alignment when the fired case exits the chamber and the case body is in a press fit to the die the neck should be aligned on exit from the die. I have cured my neck issues concentricity almost entirely by doing a skim cut on my necks and changing to bushing dies set up as I described. Everyone is free do do as they choose and what works for them.
 
Will someone please show me where saying the necks were leaving the chamber crooked in a earlier post.
 
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Will someone please show me where I've established that the neck and the body will be in alignment when the fired case exits the chamber and the case body is in a press fit to the die the neck should be aligned on exit from the die.
Today 04:54 PM
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in the post before mine you stated

The only way a chamber neck can be crooked to the chamber body is the barrel's bent at that point.

There's no way a straight reamer can make just the neck crooked.
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I think that pretty much establishes that a fired case exits the chamber with the neck and body expanded to the dimensions of the chamber. Once a case is fully inserted in a full body sizing die it is being cold extruded to fit the sizing die. A floating bushing is just that, it is free to move to the point of least resistance on the X axis as the ram is raised. Once the bushing hits the bushing retainer the neck is sized to the extent that the neck enters the bushing. Many bench rest reloaders only neck size the amount of neck that actually has contact with the bullet when the bullet is seated. Partial neck sizing makes sense because any sizing below that has no effect on anything and could possibly help align the case in the chamber when the bolt is closed. I think I may try that
 
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