Where to measure runout on VLDs?


Well-Known Member
Mar 11, 2012
Brookings Oregon
I was loading up some 120 amaxes this am. I use a 21c runout gauge and its precise to .0005. My necks were max .0005 empty. Loaded was the same as well as the ogive. But when I put the needle half way from the ogive to the tip I got about .001 to .0015 runout. is this telling me the bullets arent that precise? I have never loaded this kind before.
I know it’s not a real eld but it ain’t a Spitzer either. Just wondering..
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The ogive is the entire nose curvature.
Do you mean bullet bearing -vs- half way down ogives?
There is no bullet maker so bad as to put out bullets with 1/2thou of runout.
Actual bullet runout is typically incredibly low, requiring a juenke machine to detect it.
Excuse my slang!!

Anyhow I figured that the runout was just amplified as it extended out from the neck. So .005 at the shank by the case mouth turns into .001+ towards the tip as the bullet is long for its diameter.

The question really was where do benchrest type reloaders typically measure runout on extra long bullets and what do they consider acceptable at that spot? I usually measure it where I mentioned which is about half way from the ogive shoulder to the tip.
Thanks. That has been my goal also. Every now and then I'll do a batch that are dead on like the ones I mentioned in this post but most of the time I am between 1 to 2 tho on the bullet bearing surface when I spend the effort to uniform my cases.
For me and my rifle/repetitive non benchrest shooting style I think that anything under .005 will not show a difference. But psychologically it makes a difference knowing that I am using precise ammo. Plus reloading is boring to me unless it is challenging.
I measure on the exposed bearing surface also.

Measuring out on the ogive amplifies the readings for me too. I think that if the bullet is seated and any miniscule angle whatsoever, that angle will increase closer to tip of the bullet.

Not sure how accurate those ogive readings are anyway, because of the angled surface on the ogive that the arm of the gauge must make contact with. I'm sure a machinist could expand on that explanation a bit, but I don't think it is an optimal place to take a reading.
A picture is worth a thousand words.

As you can see on the OP type runout gauge the closer to the bullet tip the more runout you will have.


I have both gauges pictured below and the Hornady gauge will read half of what the RCBS gauge does.

Food for thought, the Hornady gauge holds a case like a chambered full length resized cartridge would be held. Meaning the rear of the case is held by the recessed bolt face and by the bullet in the throat. And the case body do not touch the chamber walls and have no guiding effect on the bullet.


Bottom line, is the case body egg shaped or is the neck off center when you spin the case on its body. So do you full length resize or neck size your cases. And a full length resized case is more forgiving with runout and the bullet alignment with the axis of the bore.
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I own both the RCBS and Hornady runout devices(shown above). I agree that the Hornady will understate runout when the values are very high, but much less so at typical ranges. Between <.001-.005” of runout, tested with my FL sized Lapua Brass with 140 Berger VLD’s measured off the bearing surface, the RCBS will give readings that are only .001-.0015” higher. With most of my runouts for my rifles running less then .003”, I would consider either device accurate enough for my testing. I find the Hornady easier and faster to use compared to the RCBS which requires some dexterity keeping the case in position while turning it to get a good reading.
Below Mr. Salazar is talking about the benefits of full length resizing vs partial full length resizing or neck sizing. And a full length resized case has more "wiggle room" to let the bullet be self aligning with the axis of the bore. Meaning as the late Jim Hull of Sierra bullets test lab would say, "The cartridge should fit the chamber like a rat turd in a violin case."

Meaning the Hornady gauge above holds the cartridge like it would be if chambered in the rifle.

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."

So you can see from reading above a neck sized case if it warps when first fired can cause the bullet to be out of alignment with the bore. So again a full length resized case is more forgiving with bullet alignment with the bore. But most people spin the case on its body and your runout can be caused by a egg shaped case body. Meaning spinning the case on the case body would be more appropriate with neck sized cases.

So again, where is the runout coming from, a egg shaped case or a off center case neck.

And the military considers match grade ammo to have .003 or less bullet runout.
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I can understand the centerline/concentricity views from folks who can't make straight ammo. But bananas do not center in chambers without chambered tension points.

These tension points are not good for accuracy, so folks who can't make straight ammo reach for big FL sizing to create more clearances(which is what caused the bananas in the first place). And then their obviously bad results seem improved by more clearances. Hence the calls for, often to insistence, that big sizing/clearances are prerequisite to good results.
I call it tail chasing...

Of course many reloaders can make straight ammo, having very low TIR -as proven on a v-block runout gauge. Just a different approach to reloading.
The reloader does not make banana shaped cases.

Warped banana shaped cases are caused by cases that are thinner on one side of the case than the other side, and expand more on the thin side side of the case when fired. And when these type cases are fired they warp and become banana shaped.

NECO Concentricity, Wall Thickness and Runout Gauge.

"The NECO, patented, Case Gauge is the most versatile instrument available for measuring the various accuracy determining factors of cartridge cases, bullets and loaded ammunition. No other gauge can measure all of the following: 1.Banana curvature of case. 2.Wall and neck thickness variations. 3.Case head squareness. 4.Banana curvature and out-of-round shape of individual bullets. 5.Runout of seated bullet. 6.Total runout of loaded cartridge."

Bottom line, at the Whidden custom die website they tell you they get the most concentric cases from non-bushing full length dies. And the quality of the case and its uniformity plus the chamber governs what happens to the case when its fired.

And Forster full length benchrest dies with their high mounted floating expander will produce resized cases with very little to no neck runout.

And a warped banana shaped case that is only neck sized will be misaligned with the axis of the bore. Meaning the case will be pushing the bullet out of alignment with the bore because the case is egg shaped, and touching one side of the chamber.

Click on the image of Kevin Thomas of Team Lapua USA posting below to enlarge.
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If you've ever measured a new -vs- fire formed case you'd know that firing does not cause runout. It removes much of it.
Sizing of thickness variance causes runout.
The greater the sizing here the greater the runout produced.

Folks, where minimal runout is desired, cull brass by thickness variance, and MINIMALLY size every aspect of your cases. Yes, custom dies are very useful for this.
And, there is absolutely nothing wrong with partial/bushing neck sizing. Not only can you make straight ammo with partial neck sizing, but you're also not bringing donut area into neck tension, as you will/do with FL sizing of necks.
If you've ever measured a new -vs- fire formed case you'd know that firing does not cause runout. It removes much of it.

I'm sorry but if the case is thinner on one side when fired the case body becomes egg shaped. Meaning the thin side of the case is bulging more after firing. Then when the case is full length resized the sizing forces cause the base of the case to tilt and no longer 90 degrees to the axis of the bore. And the amount of shoulder bump and head clearance will eliminate any tilting of the case if it was touching the bolt face.

So go back and read what Mr. Salazar was saying in my post #10 and how full length resizing eliminates the case body from having a effect on bullet alignment. Meaning how a warped banana shaped neck sized case can effect bullet alignment. Or as the late Jim Hull and Kevin Thomas said "The case should fit the chamber like a rat turd in a violin case".

So again when you spin the case on the body of the case in a runout gauge, is the runout caused by a egg shaped case or a off center case neck.
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