Bullet runout or concentricity

[6BRA]

Since my runout on the bearing surface of 98 percent of my loads is less than .0015.
I'll never need to test or care to test. Just stating my opinion. And we know what those are like.....

My case neck runout is always less than .0005 and sometimes .0000.
Once I learned how, the 21st Century tool does not get used much anymore.

Mike

 

[HotRod30-8]

Although I didn't read every post on this thread and maybe repeating someone else. I'm only stating how I approach getting bullets straight as possible. Not sure how much it helps in accuracy, but it does make me feel better that my handloads is as perfect as possible for long range, for 200 and 300 yds it may not be as critical to XC shooting in looking for .003 or less runout.

For myself I try for a .0015 runout, that's a deflection of .003 total dived by 2. What I do to achieve this goal is to:
- Anneal the cases before resizing the case with a FL bushing die set.
- Trim the cases ensuring that there is a good inside chamfer of the neck.
- Placing the bullet in the case as straight as possible and place on to the shell holder and then seating the bullet.
- The bullet seating stem must be made to be used with a VLD bullet design standard seating stem for normal bullets.

A standard seat stem with VLD bullets will not do well keep the bullet straight as possible while being pushed into the case. Annealing the necks also helps as the brass is tempered to be softer allowing the brass to expand easier allowing the bullet to seat straighter than brass that is very hard. Turning the necks also helps if you choose to do it.

 

[Webster]

I think the throat aligns the bullet when chambering it.

Also, wouldn't traveling down a 22" barrel being smashed by the rifling have a greater influence on the bullet. Tiny variations in bore dimensions are swaged into the jacket and core. Maybe that's what determines a great barrel. Everyone knows there are average and great barrels. It has to be bore dimensions and how straight it is. Before a barrel is rifled they have to drill a perfectly straight and round hole 24" long before the rifling is done.

 

[paulT]

The neck sizing may be to blame. I've shot .007+ runout factory ammo with SMKs and they shoot fine, but I personally wouldn't accept that slop in my loads.

Neck bushings both floated and tightened down gave me the worst runout. I went to Body dies and Lee Collet neck dies to get it down to +/- .001-.002 or so.

I do use the Wilson seating dies too so I never even have to check runout anymore.

Do you find best results by sizing with body die first then sizing the case necks with the Lee Die.

 

[ArtinNC]

In my opnion , I use a bullet seating die made with the same reamer that made my gun chamber and use a Wilson top and stem . And believe that is the best you can get .

 

[6BRA]

Let's think of this another way.
If you full length size and allow the case to self center in chamber and bolt face, then ram a round that is off .005 or .007 in the freebore.
What happens to your free floated case in regards to chamber and boltface? If you twist 1 way the case isn't going to be centered and float. As far as no difference on target...lol. to what degree of accuracy are we talking? 1moa or .25 to .30moa at 600 and beyond. I would bet that none of the top 10 competitors at any large event will allow this kind of runout.

 

[Webster]

Let's think of this another way.
If you full length size and allow the case to self center in chamber and bolt face, then ram a round that is off .005 or .007 in the freebore.
What happens to your free floated case in regards to chamber and boltface? If you twist 1 way the case isn't going to be centered and float. As far as no difference on target...lol. to what degree of accuracy are we talking? 1moa or .25 to .30moa at 600 and beyond. I would bet that none of the top 10 competitors at any large event will allow this kind of runout.

If the case diameter is smaller than the chamber, which it is, it isn't self-centered with the bore, it's laying on the bottom of the chamber. The centerline of the case does not lay centered with the bore in the chamber. The case body is tapered which means cartridge lays in the chamber tilted downward by the amount of clearance.

I see no comments about my previous post about traveling down the bore and being centered and smashed by the rifling. Did you ever see what the rifling engraving looks like. It's a massive whack on the bullet. Looks like a force that would easily offset any misalignment in the case neck.

 

[Murray Brook]

Do you find best results by sizing with body die first then sizing the case necks with the Lee Die.

I do this for 6 different cartridges. What I have found is that the best way to accomplish this is by using the Lee collet die first followed by the body die. In appx 20% of my cases I found that using the Lee die last would slightly change the shoulder bump #'s on my cases. I noticed that about 1 in 5 cases would chamber with a little resistance. Checked these cases with my comparator and sure enough the bump changed. Might not have much of an effect if your bumping .003, but will make a difference when trying to attain .0015 bump. JME

 

[Alex Wheeler]

I have tested this a few times. I know other guys that have as well. The funny thing is how similar the results are. The typical answer is they were so close it was a wash but the crooked rounds actually shot a little smaller.... now why is that?

 

[Fire Dog]

F Class John did a video on that very subject...
The conclusion seemed to be that it just did not make a lot of difference...

 

[markm87]

Do you find best results by sizing with body die first then sizing the case necks with the Lee Die.

I never tried doing the neck first. I have just done neck only with no cleaning, sizing or anything on once fired factory ammo.

 

[Webster]

No runout at all would be ideal. Wouldn't perfection be great!

I am not sure what the least acceptable runout should be. I have only recently purchased a gauge and the runout I got on my latest 308 Win loads ran from a low of .002"(4 out of 15) to .007-.008 for the rest. I think that is not good.

I am using Lee dies. I think that a better bullet seating die would go a long way toward correcting my runout problem. If so, what bullet seating die would you recommend ?

I am using Winchester Match Brass.

Info relating to how well the bullet and case are centered in the chamber.

Just went to the SAAMI website and compared chamber dimension to case dimensions. Looks like you have to become a member to see the standard drawings. New cartridges not made official yet are on the website and copy written. All the cases are similar as far as clearances. If you look at the numbers there is .010” clearance between the chamber and case. Why are you worried about bullet runout?

From the 6mm Creedmore drawing:
At the neck shoulder junction, the difference between the case and chamber is dimension is 0.010”.
.330” below the corner of the neck/shoulder the difference is 0.010”.
Just in front of the case neck the chamber is .2435” (½” thou centering the bullet).
The chamber is 0.004” bigger than the case neck diameter.
No dimension given for the end of the forcing cone.
The cartridge is not centered in the chamber.

Add to this the bullet being rammed thru 24” of rifling. All new dimensions that should wipe out any bullet run out.

 

[Dave M.]

The neck sizing may be to blame. I've shot .007+ runout factory ammo with SMKs and they shoot fine, but I personally wouldn't accept that slop in my loads.

Neck bushings both floated and tightened down gave me the worst runout. I went to Body dies and Lee Collet neck dies to get it down to +/- .001-.002 or so.any

I do use the Wilson seating dies too so I never even have to check runout anymore.

It is very important when sizing with bushing dies to raise the brass into the die somewhat slowly to allow the bushing time to self align. A bushing should always be allowed to free float and running the brass quickly up into the die is akin to locking the bushing down because the brass pushes the bushing up and prevents it from aligning properly.
Dave

 

[Dave M.]

Since my runout on the bearing surface of 98 percent of my loads is less than .0015.
I'll never need to test or care to test. Just stating my opinion. And we know what those are like.....

My case neck runout is always less than .0005 and sometimes .0000.
Once I learned how, the 21st Century tool does not get used much anymore.

Mike

I agree that my concentricity tool never gets used anymore, but I’m willing to bet that you are not making all of your ammo at less than a half a thousandth of TIR on the necks. I’m about as anal as a reloader can be and I’m certain that even I am sizing brass that occasionally slips outside of a half thou. I’ve read many of your posts Mike and I respect you as a shooter and reloader. I’m thinking you and I should dust off our 21st century gauges and measure the TIR on the upper portion of the necks on a 30 piece study. I don’t mind making a video of my 30 pieces and perhaps you can do the same. I don’t have any immediate reason to reload at the moment, but perhaps we can learn from each other. I’ve already proved to myself (and likely you have as well) that concentricity of bullets seated into brass is rather meaningless on the target. Although it is likely far more important, I’ve also shot ammo with virtually no neck TIR versus ammo that measured as much as 3.5 thou TIR on the necks, and although the ammo with no TIR runout technically scored better at 1000 yards, the total group size in the ammo with 3.5 thou neck runout had a smaller group size. These were shot in two consecutive matches on the same day with very favorable winds.
20 shot groups:
Match 1 with virtually no TIR
200-10X (0.96 MOA group size)

Match 2 with 1.5-3.5 thou TIR
199-10X (0.90 MOA group size)

Dave

 

[drop_point]

For what it's worth, I asked a question similar to this about run out a few months back and got pretty much the same answers you're getting. I was shooting a 30BR at 1-200 yards. I took my reloads that had .001-.002 and ones that had .003-.006. I shot 5x5 with both sets of reloads and saw no difference in group sizes. That being said, I still dont want runout.

I found that the runout in my situation was coming from the press itself. Just something to maybe think about. For my 6br I FL size without the expander ball and then get the proper neck tension with a mandrel die.

I would like to hear more about the press inducing runout. Care to share more details?

 

[6BRA]

I agree that my concentricity tool never gets used anymore, but I’m willing to bet that you are not making all of your ammo at less than a half a thousandth of TIR on the necks. I’m about as anal as a reloader can be and I’m certain that even I am sizing brass that occasionally slips outside of a half thou. I’ve read many of your posts Mike and I respect you as a shooter and reloader. I’m thinking you and I should dust off our 21st century gauges and measure the TIR on the upper portion of the necks on a 30 piece study. I don’t mind making a video of my 30 pieces and perhaps you can do the same. I don’t have any immediate reason to reload at the moment, but perhaps we can learn from each other. I’ve already proved to myself (and likely you have as well) that concentricity of bullets seated into brass is rather meaningless on the target. Although it is likely far more important, I’ve also shot ammo with virtually no neck TIR versus ammo that measured as much as 3.5 thou TIR on the necks, and although the ammo with no TIR runout technically scored better at 1000 yards, the total group size in the ammo with 3.5 thou neck runout had a smaller group size. These were shot in two consecutive matches on the same day with very favorable winds.
20 shot groups:
Match 1 with virtually no TIR
200-10X (0.96 MOA group size)

Match 2 with 1.5-3.5 thou TIR
199-10X (0.90 MOA group size)

Dave

Next time your through Cincinnati, bring your wallet. It's mommas secret recipe. I should be able to post video to one drive and share. Give me a day.
I grabbed 2 pieces at random here is a link. I don't have time to film 30 pieces nor am I steady enough.

Runout

drive.google.com

 

[Webster]

I would like to hear more about the press inducing runout. Care to share more details?

Don't understand. The die shapes the cartridge, the press just pushes it in?

 

[DShortt]

But what about in a factory cut chamber, that has more like .005"+ of radial clearance? Maybe the canted bullet thing actually matters then?
Every time I read about a test it always involves a rifle with a custom barrel that I can assume is a lot tighter in the neck area than an average Joe's factory rifle.

Perhaps I'll have to try this out for myself.
As an average Joe, I have access to such rifles.

So here's my theory. Keep in mind, anytime I see something that contradicts my theory, I investigate why and change my thinking accordingly.

So. At this particular point in my experience, run-out is a problem when the chambering is loose. If the chambering is tight, it's not of any particular concern. This may even partially explain the 'shot out barrel' phenomenon. In other words, it might be possible to extend the shooting life of a barrel if you load concentric ammunition.

Just my opinion and worth exactly what you paid for it.

Edit to add : if the chamber/throat is cut inconcentric with the bore, it *might* be OK for a hunting rifle. But the overwhelming majority of members of this forum would want to use it for an unconventional suppository for whomever made it. Ain't never gonna shoot small groups.

 

[Dave M.]

Next time your through Cincinnati, bring your wallet. It's mommas secret recipe. I should be able to post video to one drive and share. Give me a day.
I grabbed 2 pieces at random here is a link. I don't have time to film 30 pieces nor am I steady enough.

Runout 1

drive.google.com

Runout 2

drive.google.com

You will have to.open in the drive app. Those marks are 5 t enthousandths

Second piece looks like about 1.25-1.5 thou of total run out. Very stable and more than capable of winning top level matches. I’ll load a few videos if I can figure out how tomorrow. I’ll have to size a few pieces and then just select 3-4 pieces at random out of the bunch. What sizing process are you using?
Dave

 

[6BRA]

Second piece looks like about 1.25-1.5 thou of total run out. Very stable and more than capable of winning top level matches. I’ll load a few videos if I can figure out how tomorrow. I’ll have to size a few pieces and then just select 3-4 pieces at random out of the bunch. What sizing process are you using?
Dave

They are both under .0005. I'll find a holder for my phone to film. That needle is barely moving. Those rounds have .004 neck tension. I am also jumping the wheel because I am only using 1 finger. I normally run the wheel between my index and thumb.