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Does concentricity matter?

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captainmorgan460

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Dec 16, 2017
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Is there a benchmark on what is good or not good for a concentricity value to obtain a practical level of accuracy? I'm measuring about 0.0015" TIR on the neck after sizing and 0.004" on the bullet after seating. Does anyone pay any attention to concentricity when loading for PRS/NRL style of shooting?

Process I'm doing right now for 6.5 CM and 147 ELD-M load is de-capping with the Lee tool first. Clean. Hornandy 1 shot lube. Size with RCBS rock-chucker and Redding FL sizing die. Trim and chamfer. Seat with Redding competition seating die. Accuracy for this load has been fine at 3/8" to 1/2". SD's around 8-10.
 
Consistency is important. If most rounds are within a certain concentricity range and it shoots well as in your situation then I would not worry about getting the numbers tighter. I doubt you can do better by squeezing out another thou for less runout. What you dont want is a big extreme spread in your runout range. A couple 0.0004” , then a couple 0.0007”, etc. If that’s the case then diagnose what is causing it. It is from the sizing operation, the seating operation? Troubleshoot then correct.
 
Years ago I separated some well known and popular factory ammo by concentricity into two groups.
>.004 and <.004. 25 rounds in each.

Shot them on the same day on same rifle.

The results were very noticeable with the straighter rounds being an obviously smaller group.
 
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I like my TIR measured at or near the ogive to be .004 or under. Some lost that come out under .002 seem to shoot a bit better.
I have always wondered why the chamber did not straighten them. Suppose if it does the round is still under stress?
 
I load in batches of 50 or 100 and then sort all the rounds by .001 of runout. Like Steel Head said earlier I too had done tests with runout. I took some .003 and .006 223 rounds and shot 2 groups of 5 of each round robin. The .003 groups averaged .450 while the .006 groups average .700. It showed me that yes runout effects accuracy but also doubling the runout doesn't double the group size. This was back when I was shooting NRA High Power and the 10 ring is 2 moa so even a runout of .006 would have all been in the X ring. Now that I am shooting F-Class I use my .002 or less for record. .003's maybe for sighters, the rest are for doing chrono testing or just practice at 100.

David
 
Anyone else ever wonder if the reason concentricity is debated so much is that it's effect (lack of concentricity) is non-linear in relation to bullet length? As in, the longer the bullet is, in relation to the diameter/caliber, the more effect the TIR error is amplified, exponentially?

Just thinking out loud here, since I've had some .223 55gr reloads show much better accuracy at 550yds, than some 75gr ELDM's at the same distance, using the same dies. The barrel is a 1-8 twist, so stability isn't a factor. And the inaccuracies shown, were just weird random fliers.

At any rate, this is what has led me to believe that concentricity does matter, and more so when the bullets are long for caliber...

Again, I have no hard science or test to back this up, just more anecdotal (observed) evidence.
 
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Thanks for the feedback. For now I'm going to load and shoot as is. Seems like there is some correlation between accuracy and concentricity but with a diminishing return. Has anyone measured the difference between say a redding competition seater vs forester vs lee hand die?
 
I use a Redding Competition Seater. I get about 50% .001 and about 30% .002 with the rest usually 3’s with a few 4’s

David
 
Fig said:
I think having the die float is the key rather than the brand of die. I have some of every brand and they all seat a bullet straight when they float.
Click to expand...

I saw that posted before here about floating with an o-ring. Is it hard to keep the loaded length consistent with that? Or are you talking using a press like a co-ax?
 
FWIW, I took out ten loads last week. Six rounds were <0.002" ; four rounds were pretty bad 0.004-0.009". This was lake city range pick up brass on it's 3 rd firing. Shot two groups of 5. The group that contained the poor concentricity rounds shot about 1/4" better at 100 yards. Both groups were a bit over 1/2 MOA, IIRC.
 
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Yes. It matters. Sometimes.

I switched to LE WIlson bullet seating chamber dies, and am now always within 1/1000th of an inch concentricity.

7091665


Seems to me its worth it just to eliminate "out of concentricity" as a complicating factor.
 
garandman said:
Yes. It matters. Sometimes.

I switched to LE WIlson bullet seating chamber dies, and am now always within 1/1000th of an inch concentricity.

View attachment 7091665

Seems to me its worth it just to eliminate "out of concentricity" as a complicating factor.
Click to expand...
Concentricity is determined long before you seat a bullet. No die, including that one will bring it back in line.
 
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Milo 2.5 said:
Concentricity is determined long before you seat a bullet. No die, including that one will bring it back in line.
Click to expand...

My concentricity gauge says otherwise. All the other dies I have tried Leave me 3 to 5 thousands out or even a little more. These Wilson dies get it spot on every time.
 
That said, my 6.5 creedmoor rounds were well out of concentricity yet repeatedly shot 0.36 to 0.50 MoA.




Does concentricity even matter? Maybe. It matters if / when matters.
 
Seems the best answer is "it can". The problem is that there are many variables that play into it (the chamber, the bullet, the brass, how far out of concentric...). It's just one more thing to keep an eye on.
 
I think the old adage "You have two ears, and one mouth" applies here Garandman (rather than providing a contradictory statement).

With that being said, Milo, can you expound on your thoughts/statement? I'm honestly am curious as to why you state what you do, and your reasoning behind it.

I have a feeling there are assumptions being made for each the two opposing statements, and am curious as to what those are...as are others, I'm sure.
 
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MarinePMI said:
I think the old adage "You have two ears, and one mouth" applies here Garandman (rather than providing a contradictory statement).
Click to expand...


My personal experience in what I have seen and done has said his assertion is wrong. Are you too sensitive to have someone disagree with you?

I get all kinds of off topic personal attacks and insults from this forum. I don't care. It's the Internet. None of your opinion about me matters to me.





Toughen up people.

Now… please stay on the OP 's topic and don't make this thread about me also. This thread is about concentricity ... not a bunch of yahoos opinions about me.
 
MarinePMI said:
I think the old adage "You have two ears, and one mouth" applies here Garandman (rather than providing a contradictory statement).

With that being said, Milo, can you expound on your thoughts/statement? I'm honestly am curious as to why you state what you do, and your reasoning behind it.
Click to expand...
If your brass is not concentric before seating a bullet, no die can rectify it. It is just as easy to check the necks, both inside and out with your gauge as it is to run it on the bullet, all I said.
If indeed, his other dies are the cause of the runout, most times that can be fixed too.
I would never advocate someone going to an arbor press system unless extreme accuracy is desired, and even then so, more to measure seating force rather than straighten ammo.
I owned the K&M arbor, with force pack, and Wilson inlines for 3 hours, I seated close to 50 bullets from 3 different cases, 2 Dashers and an 6XC. It did not tell me anything I was already aware of, just a giant pain in my ass. The prices I listed the crap at resulted in immediate sales.
YMMV
 
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MarinePMI said:
I have a feeling there are assumptions being made for each the two opposing statements, and am curious as to what those are...as are others, I'm sure.
Click to expand...

I gave my data set and fact based reasoning above. I have tried most different die sets and the only one that consistently gets concentricity within 1 / 1000 are the Wilson bullet seater chamber dies. The dies used being the only variable in my loading session and Wilson are spot on and RCBS in Lee and hornady and even Forster and others are 3 to 5 thousandths out.
 
Milo 2.5 said:
For fucks sakes, go straighten up your bc post. The clown here is obvious.
Click to expand...


You apparently are not aware of how to have a conversation of difference of opinion without profanity and insult...



I guess public schools don't teach that anymore
 
garandman said:
I gave my data set and fact based reasoning above. I have tried most different die sets and the only one that consistently gets concentricity within 1 / 1000 are the Wilson bullet Cedar chamber dies. D Di use being the only variable in my loading session and Wilson are spot on and RCBS in Lee and hornet I and even Forster and others are 3 to 5 thousandths out.
Click to expand...
Breathe numbnuts, you're not making any sense here.
Of coarse a Redding or a Whidden are not mentioned.
 
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To the OP… I would be very suspect of opinions I get from people who don't know how to have an adult Conversation... If they are that juvenile about a discussion you have reason to doubt the rest of their knowledge base. ... Which could be little more than that extracted from Internet forums.
 
Milo 2.5 said:
Breathe numbnuts, you're not making any sense here.
Of coarse a Redding or a Whidden are not mentioned.
Click to expand...


Fine. They are great dies. Use them. I don't care. That's not what's being discussed here. You are moving the goal posts..



You made the claim that the bullet seater can't change the Over all concentricity of the round



I've loaded using different seater dies and your statement is untrue.
 
garandman, you may just want to chill a bit. I was asking a question of Milo to understand where his logic was derived.

It would seem to me, with Milo's response, that an adult conversation is taking place (thank you Milo, for your response).

Perhaps when you post the notion of uncivil and personal attacks, you should take a look in the mirror before accusing anyone. I'm trying to give you the benefit of the doubt here (that you're just not quite up to speed on internet protocol and civility), but you're starting to make this difficult.
 
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MarinePMI said:
garandman, you may just want to chill a bit. I was asking a question of Milo to understand where his logic was derived.

It would seem to me, with Milo's response, that an adult conversation is taking place (thank you Milo, for your response).

Perhaps when you post the notion of uncivil and personal attacks, you should take a look in the mirror before accusing anyone. I'm trying to give you the benefit of the doubt here (that you're just not quite up to speed on internet protocol and civility), but you're starting to make this difficult.
Click to expand...
Im sent.
 
Concentricity matters when/if it matters. The only real way to test it is to load up the exact same load into batches. One checked for concentricity and the other known to be out of concentricity and then see if they have different results on target.


Repeat that Test several times and then draw your own conclusion.



Even my personal experience really won't matter in your gun on your range in your groups and accuracy. I provide it only as a singular data point for your research.
 
MarinePMI said:
garandman, you may just want to chill a bit. I was asking a question of Milo to understand where his logic was derived.
Click to expand...

Then why did you start that post with a personal shot at me basically telling me to shut up?



Is there a special fee that needs to be paid on this forum to have a differing opinion than I haven't paid yet?



Is this place such a cluster of total group think that other people who disagree with the approved position are not allowed to say so?
 
garandman said:
Then why did you start that post with a personal shot at me basically telling me to shut up?



Is there a special fee that needs to be paid on this forum to have a differing opinion than I haven't paid yet?



Is this place such a cluster of total group think that other people who disagree with the approved position are not allowed to say so?
Click to expand...

Check your IM's for a response.

I would remind you that many of the contributors to this forum have collectively, centuries of experience, and are far from the "group think" type. No, primarily the "old hands" here are the quiet professionals, and while opinionated alphas, understand that the devil is in the details.
 
MarinePMI said:
garandman, you may just want to chill a bit. I was asking a question of Milo to understand where his logic was derived.

It would seem to me, with Milo's response, that an adult conversation is taking place (thank you Milo, for your response).

Perhaps when you post the notion of uncivil and personal attacks, you should take a look in the mirror before accusing anyone. I'm trying to give you the benefit of the doubt here (that you're just not quite up to speed on internet protocol and civility), but you're starting to make this difficult.
Click to expand...
I did not need to call him a clown, that is on me.
You have been here longer than I, I have posted my quest for concentricity in the past, not that I expect anyone to remember. lol
It all started with a .003" number, I spent a ass ton of money getting it down to .0015" without any gains downrange. I went even farther with a diff brand of sizing dies, and for the most part cut all my cases runout to .0007 avg.
Here is my perspective, yes today my ammo shoots better than back then. But, I also put way more time into development of that ammo. Plus I also feel the quality of the rifles I have built today are far superior to what I was shooting back then when I went on the tirade for perfection.
So unless I enter the 1000 yard benchrest game, I am not concerning myself with concentricity today. Does that mean I will not check it out if my results are not what I expect, well NO, I had to just 2 weeks ago, turns out my extra large jaws on one of my coax's was tilting one certain Dasher slightly while I did a partial neck treatment with a neck bushing die. Easy find, easy fix.
 
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Milo 2.5 said:
I did not need to call him a clown, that is on me.
You have been here longer than I, I have posted my quest for concentricity in the past, not that I expect anyone to remember. lol



<snip>
Click to expand...

Awesome post brother. I totally respect that and will read it through a couple a times to try to glean as much as I can..



My personal experience, while different, is my personal experience and really has very little bearing beyond that reality for me personally.


Fact is each person's reloading situation has so many dozens of variables that it's hard to make total absolute assertions That my experience will be universally true for others
 
garandman said:
Awesome post brother. I totally respect that and will read it through a couple a times to try to glean as much as I can..



My personal experience, while different, is my personal experience and really has very little bearing beyond that reality for me personally.


Fact is each person's reloading situation has so many dozens of variables that it's hard to make total absolute assertions That my experience will be universally true for others
Click to expand...
Right.
I leave way too much out when I post. What I should have said is, a seater cannot correct runout, but yes, one can in fact induce some.
Also, I do not repeat what I have read, or heard or overheard, I speak from experience only. If I pass on someone elses ideas, I state it upfront.
 
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Don't change anything except index each cartridge. Mark the cartridges with a sharpie so that each bullet leaves the muzzle pointed in the same general direction. Try it sometime. Call it a test. Groups should gather at the same point of the clock. Then decide if it is material or not. Uh, don't do this in the lands. If you see a material change then your rifle is a POS, which requires having to make up for it at the loading bench. Not that there is anything wrong with that.
 
Dstoenner said:
I use a Redding Competition Seater. I get about 50% .001 and about 30% .002 with the rest usually 3’s with a few 4’s

David
Click to expand...

I get the exact same thing with basic Lee seating die. The Lee came out a very long time before that Redding Competion die. People just got bored with the Lee and demanded to pay more for a seating die.
 
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The reason concentricity matters is if the projectile isn't inline with the centerline axis of the bore it will enter the bore cockeyed and exit the same way. Think of a wounded duck football flying through the air as opposed to a tight spiral.
 
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garandman said:
Yes. It matters. Sometimes.

I switched to LE WIlson bullet seating chamber dies, and am now always within 1/1000th of an inch concentricity.

View attachment 7091665

Seems to me its worth it just to eliminate "out of concentricity" as a complicating factor.
Click to expand...
People precision load on, and swear by Dillon machines here. They float their seating dies with O rings and have other tricks. I have blue too, but only load pistol and 5.56 on it. I use a Forster.

I have never seen anyone talk about hand dies and an auger press for competition here. With matches that can run more than 220 shots over two days even those obsessed with precision must make some accommodation to time. I know of no one using hand dies or loading at the range in the most prevalent sports.

We like small groups, but the reality is that a rifle that shoots under a minute is good to go.

I have a nice 6PPC and hand die loading set up for it, but when I want to talk that I go to accurateshooter, not SH. It’s apples and oranges.
 
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Fig said:
People precision load on, and swear by Dillon machines here. They float their seating dies with O rings and have other tricks. I have blue too, but only load pistol and 5.56 on it.

I have never seen anyone talk about hand dies and an auger press for competition here.
Click to expand...

To date, I load both 9 mm and 300 blackout on my 550C. Maybe 45 one day. Never tried it for a more precision load though when I check the powder throws they're usually within a 10th of a grain or so.

For people who compete, I would imagine you've got to use A 550 or progressive to crank out the quantity you need.

My only point about Wilson bullet seaters is that they get concentricity dead on.
 
cornhusker86 said:
The reason concentricity matters is if the projectile isn't inline with the centerline axis of the bore it will enter the bore cockeyed and exit the same way. Think of a wounded duck football flying through the air as opposed to a tight spiral.
Click to expand...


Agreed.


In my experience I have shot rounds in 6.5 Creedmoor that were 3 to 5 thousands out of concentricity that still grouped under half MoA.

YMMV.

Maybe I just got lucky A dozen different 5 shot groups in a row. Lol
 
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