Concentricity Adjustment and Neck Tension

BearDog

Well-Known Member
Joined
Feb 8, 2012
Messages
154
Location
Washington
This is more of a theoretical question I haven’t found the answer to...

After seating a round, I always will put it in a concentricity tool, and if the runout is greater than .002, I will use the adjustment tool to straighten the round until it is less that .002. In doing that, am I creating a variance in neck tensions across my rounds, and possibly impacting variables like pressure, velocity, and potentially overall accuracy?

I’m using a RCBS single stage press, Redding Premier Dies, and Hornady Concentricity Gauge.
 

Mikecr

Well-Known Member
Joined
Aug 10, 2003
Messages
5,549
Location
NC, oceanfront
If your runout is >2thou as seen on a neck bender, the actual runout is way higher still.
And while your lowering indicated eccentricity on the tool, your ammo is still crooked as all get out.
Then, chambering crooked ammo can lead to chambered pressure points(depending on clearances).
This is where shots begin to throw.
Wiggling seated bullets at abstract angles & amounts won't help with desired CBTO either.

As far as tension variance from it, I'm thinking it's minor to these potentials, but hard to say.
 

nksmfamjp

Well-Known Member
Joined
Jan 5, 2004
Messages
1,109
I don’t know, but I’ve straightened rounds.....took them from like 0.01” max to 0.002” max....Groups doubled in size. No fancy tool, just pushed on the side of the the bullets....bad!
 

Mikecr

Well-Known Member
Joined
Aug 10, 2003
Messages
5,549
Location
NC, oceanfront
A better plan is to throw away the Hornady and live with what you have, or,, throw away the Hornady, pickup a v-block type runout gauge, and discover what your runout actually is.
Then you can figure out whether your runout matters, and if so, go after the root causes.

Forget concentricity, as it's a misnomer for eccentricity.
A concentric item holds the quality of low eccentricity.
Concentric is w/resp to centerline. Where it is concentric, it has been centered.
This rarely applies to chambered ammo at rest, and is in no way beneficial.
The old notions that you can get bullets pointed true to barrel centerline are pure rubbish.

Straight ammo holds the quality of low runout. If it were centered it could also be described as concentric.
This is the quality to reach for, in that straight ammo can rest stress free as chambered.
When the bullet is neck released on firing, it will bore communicate with a quality established through full seating testing.

When you force a concentric condition with high runout ammo, you have not addressed the chambered condition of that ammo. The question then is; do you have enough chamber clearance for this crooked ammo to rest stress free?
Bent2.jpg
 

DUSTY NOGGIN

Well-Known Member
Joined
Mar 18, 2015
Messages
743
Location
salt lake city
A better plan is to throw away the Hornady and live with what you have, or,, throw away the Hornady, pickup a v-block type runout gauge, and discover what your runout actually is.
Then you can figure out whether your runout matters, and if so, go after the root causes.

Forget concentricity, as it's a misnomer for eccentricity.
A concentric item holds the quality of low eccentricity.
Concentric is w/resp to centerline. Where it is concentric, it has been centered.
This rarely applies to chambered ammo at rest, and is in no way beneficial.
The old notions that you can get bullets pointed true to barrel centerline are pure rubbish.

Straight ammo holds the quality of low runout. If it were centered it could also be described as concentric.
This is the quality to reach for, in that straight ammo can rest stress free as chambered.
When the bullet is neck released on firing, it will bore communicate with a quality established through full seating testing.

When you force a concentric condition with high runout ammo, you have not addressed the chambered condition of that ammo. The question then is; do you have enough chamber clearance for this crooked ammo to rest stress free?
View attachment 211934

picture says a thousand words ..

either sort out the the runout extremes or turn your necks so once they are fired they will be straight
 
Last edited:

ButterBean

Well-Known Member
LRH Team Member
Joined
Feb 5, 2012
Messages
3,526
Location
West Terre Haute Indiana
A better plan is to throw away the Hornady and live with what you have, or,, throw away the Hornady, pickup a v-block type runout gauge, and discover what your runout actually is.
Then you can figure out whether your runout matters, and if so, go after the root causes.

Forget concentricity, as it's a misnomer for eccentricity.
A concentric item holds the quality of low eccentricity.
Concentric is w/resp to centerline. Where it is concentric, it has been centered.
This rarely applies to chambered ammo at rest, and is in no way beneficial.
The old notions that you can get bullets pointed true to barrel centerline are pure rubbish.

Straight ammo holds the quality of low runout. If it were centered it could also be described as concentric.
This is the quality to reach for, in that straight ammo can rest stress free as chambered.
When the bullet is neck released on firing, it will bore communicate with a quality established through full seating testing.

When you force a concentric condition with high runout ammo, you have not addressed the chambered condition of that ammo. The question then is; do you have enough chamber clearance for this crooked ammo to rest stress free?
View attachment 211934
I have have both the Hornady and a V-Block I find there is less than.0001 difference between the 2 so to suggest throwing away the Hornady is a personal opinion and should be viewed as such and you still haven't answered the OP's question , For the OP , Yes it will cause a slight neck tension variance but its minimal as long as you don't go crazy "Pushing" and yes it will effect overall accuracy, I would suggest ( as mentioned above) working on your resizing to eliminate the need to push, If you need any help just holler
 

nksmfamjp

Well-Known Member
Joined
Jan 5, 2004
Messages
1,109
While I agree the V blocks are pretty good, they really aren’t holding it right.

It should be aligned by pushing the case into the shoulder to align and supported to make the case body axis concentric to the centerline like a chamber. Then measure the neck and bullet runout.

The Hornady holds by the tip and base which will give less meaningful output numbers.
 

ButterBean

Well-Known Member
LRH Team Member
Joined
Feb 5, 2012
Messages
3,526
Location
West Terre Haute Indiana
While I agree the V blocks are pretty good, they really aren’t holding it right.

It should be aligned by pushing the case into the shoulder to align and supported to make the case body axis concentric to the centerline like a chamber. Then measure the neck and bullet runout.

The Hornady holds by the tip and base which will give less meaningful output numbers.
I agree with all of that but that's still don't answer the OP's question, I'm sure he appreciates anyway and no offense intended
Bean
 

Primary

LRH Assistant
Here are some related products that LRH members are talking about. Clicking on a product will take you to LRH’s partner, Primary, where you can find links to LRH discussions about these products.

 
 
Top