Concentricity, how I fixed mine

H

hounddawg

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Concentricity and runout, does it matter and how I got mine down to .001 or less. There are varying opinions on how much it affects accuracy. I think most everyone will agree that a runout of 0.005” is too much for best accuracy, and a runout of 0.01″ is really completely unacceptable. I attempt to keep the runout on my ammo less than .001.

The next question is where is runout generated? My opinion is that it can only generated during case prep if you are full length resizing and are seating the so that .200 or more of the bullet is inserted in the neck.

I do not think it can be induced during seating. Bullets are like water , electricity and people. They will follow the path of least resistance when being seated. If the inside walls of neck are concentric the bullet will be concentric. I have attempted to induce runout with bullets that have .2 or more of their length inside the neck and it takes a lot of pressure applied to the side of that bullet to do so. More than could ever be generated in a seating operation. I have been using a Forster micrometer seating die for .308 to seat my .260 Remington bullets for 10 years now and get very concentric results.

During my early attempts at getting concentric ammo I used a Redding body die combined with a Lee collet neck die and got some pretty decent ammo. Generally it would have .002 or less runout. Unfortunately Lee only makes the die in certain cartridges, the good news is they will make custom dies. It will just cost you a little extra money and time.

My next effort was to go going to full length bushing style dies. I found that by removing the expander ball from my dies and dialing in the neck OD I could get as good as result as I could with the body/collet die combo and could control the neck tension while doing so.

I still wanted to get that runout down a bit so I started doing some neck turning along with using a Wilson neck reamer. That did bring down the runout even more. But being the curious type I decided to go with the method a lot of BR shooters use and modify it a bit.

My current system gets me .0005 - 001 runout without fail.

1. - new brass gets neck turned to .012 wall thickness
2.- All depriming is done in a separate operation
3. - Brass is full length resized with the expander ball removed. Brand of die does not matter, the dies body and neck is reamed out in the same operation with a through reamer, it can't be anything except concentric.
4. - That is followed by expanding the neck using a Sinclair Gen II die with a 21st Century expander mandrel.

For me this works. I use a Lee Classic turret with a ton of float both in the turret and in the shell holder. My dies run the gamut from Whidden to Lee full length and Redding Bushing dies. I use Wilson, Redding, Forster, RCBS and Lee seaters. With all of those I get .0005 - .001 runout consistently from .223 to .308 while allowing me to dial in my neck tension


Sinclair Gen II mandrel die - $32.00 but currently unavailable

https://www.sinclairintl.com/reload...ls/generation-ii-expander-dies-prod38807.aspx

21st Century mandrels available in .0005 increments, 21.50 each and up

https://21stcenturyinnovation.com/buy-online/ols/products/caliber-specific-expander-mandrel

some small edits for typos
 
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Houndawg, i'm a bit confused on your method, i checked out the sites you posted and the Sinclair expander mandrels are all .001 smaller than the bullet calibers. Are you implying that your neck tension is only and always .001?
That doesn't seem like enough tension to me, you could probably push the bullet in further with your finger or worse if you drop or bump it.
 
I use 21st century expander mandrels not Sinclair mandrels , the last link in the OP will take you to the page for 21st Century caliber specific mandrels. They fit the Sinclair die, I just prefer the Sinclair Gen II holder to the 21st Century holder die

for a 6mm for example the 21st Century mandrels run from .240 to .245 in .0005 increments. They also sell them in kits of 10 mandrels in .0005 increments if you want to experiment with the different tensions. I just use the .221, .240, the .261, and the .305 since .003 tension seems to work good for me. But if you want to try a neck tension of .2415 you can do that

edit - note that springback may come into play here depending on how much the brass has work hardened

Here is the link again for the 21st Century mandrels


https://21stcenturyinnovation.com/buy-online/ols/products/caliber-specific-expander-mandrel
 
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Ahh, ok, I get it, thanks so much for clearing that up for me, also I'm not sure if a through reamer is a machinist tool or a reloading tool. Excuse me for my ignorance:D
 
I'm not sure if a through reamer is a machinist tool or a reloading tool. Excuse me for my ignorance
Click to expand...


a bit of an edit here. By through reamer I mean that the neck and body of the die is cut with one reamer, the same way a rifle chamber is cut. That means there is no way the neck area of a die can be misaligned with the main case body while the case is fully inserted in the die. Here is a page with pictures of chamber reamers. Reamers used to cut sizing dies are shaped in the same way and the neck and main body is cut with the same reamer when being manufactured.

https://www.triebel-guntools.de/en/chamber-reamers.html

My theory is that it is when the case is being withdrawn from the die and the expander bushing is being pulled back through the case neck that the necks get tweaked out of alignment. At that point in the process the case walls are not touching the sides of the die and can be bent easily if the bushing grabs one side of the neck or the case is cocked in the shellholder.

No way I can prove it but I do know the first step in eliminating runout is to toss that expander button and at minimum go to a bushing die

I wish I had the CAD talents of Uncle Nick so I could explain it better

through reamer is just a old school term that my Uncle taught me about a 1/2 century ago. I worked in his machine shop after school when I was a teenager learning the machinist trade by making parts for anything and everything that was brought in. It may or may not be the correct term, that was a long time ago;)
 
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I too use the Redding body die with the Lee Collet neck sizing die like you have previously done. I only use this method for 6.5 CM and .223 since these are the only calibers I use for precision shooting. My concentricity is very consistent at .001” or less with an occasional outlier that’s between.001-.002. I also turn the necks for consistent neck thickness since I feel without this a collet die wouldn’t be as effective because it’s squeezing the brass with different thickness in some spots giving different pressures on the neck sides. At least that’s my thought process.
 
@stagpanther - other than normal trimming there is nothing to take care of. I have checked neck wall thickness on cases fired 5x times after being neck turned using a ball micrometer accurate down to .0001 and the maximum change in the wall thickness was .0001 on a few cases.

@Jetinteriorguy The lee collet method worked great for me also. What got me into the mandrels was when I got into 6BR, yeah I know Lee will make me custom collet neck sizers in 6BR but it was just quicker to use a expander mandrel and FL die and the results are comparable One thing I did with the Lee collet, and I am not sure if this was essential, was to size the case rotate it 90 degrees then size again.

I also think that neck turning is essential for making precision ammo, it is not nearly as difficult as I once thought it would be and the equipment is inexpensive compared to many of our reloading toys
 
My guess for rotating 90deg with the collet die is to possibly compensate for varying neck thickness in cases that haven’t been turned. I like your notion for neck sizing and having the various size mandrel available to play with neck tension. I’d be tempted to give it a try but I’m getting more to the point of fewer rabbit holes to go down. Not because they are a waste of time, but mainly because I’ve come to the conclusion that no matter what I do as a shooter I’m basically a good solid sub MOA shooter but not a good consistent sub 1/4 MOA guy. My main reason for going through a lot of the extra little things to improve accuracy in my handloading was to eliminate my loads/equipment in determining what my abilities are, and I feel I’ve reached that point and am completely comfortable with it.
 
Remember It only takes about 40 psi of downward pressure for that bullet to go into the neck even using .003 compression. I suppose it is possible but you would have to be pushing almost 90 degrees to the axis in my opinion

Try this

Take a bullet and seat it in a case with no powder or primer. Seat using at least .002 compression and having .1 inch of bearing surface inside the neck for every .1 of the bullet diameter.

Leave the case in your press and using your thumb or some other tool press against the side of the bullet and push and see how much you can bend that neck. Then think that the bullet seater will not be contacting that bullet and pushing it at 90° to the axis like you are but probably at a angle of less than 10°.
 
Interesting notion on inducing runout. I have the Hornady runout testing setup and it has this little feature of a threaded shaft for straightening a crooked bullet by locating the spot where it’s ‘bent’ and then applying pressure to straighten it. At first I tried it and it didn’t seem to help any and my loaded ammo doesn’t really need it anyway so I never use it.
 
Ahh the Hornady bullet bender :) Then you know how much pressure it takes even when applying pressure at a 90 ° angle to get that bullet to bend the neck. Common sense says that if it takes 40 psi to get that bullet to go into the neck straight it would take 40 psi + ?? psi to get that bullet to bend the neck while it goes in. Pretty sure I would notice the extra seating pressure if it were bending the neck and it would probably shave off a bit of the bullet jacket as well if it was entering the neck crooked. It does however make the argument that you should always do a inside chamfer to help guide it in. I also like to use the Imperial dry graphite on my necks just before seating. I don't know if that helps but it makes me feel better


My theory is the bullet will take the path of least resistance and will follow the interior neck wall of the case when seating. I have seated my .260 Remington bullets using a .308 seating die for over ten years now, and I use a Frankford Armory universal for seating my .30 Grendel bullets, both come out with great concentricity even though that case neck is floating in the seating die

Now if the seating stem is hitting on the meplat instead of the ogive I know that the base to ogie measurements will be erratic, and will throw off the jump but that is another thread
 
Oh man, don’t even start me on seating stems and variations in seating depths as per the calibers location on the ogive and all the various things that affect that. That’s one deep rabbit hole I finally gave up on, and for my shooting requirements just not worth getting too exact about. I loaded a hundred rounds in my best load for my 6.5CM and loaded them long on purpose then kept bumping them down until each one was seated to the perfect base to datum point on the ogive of each bullet. Proceeded to shoot ten-ten shot groups with literally no discernible difference than if I set the seating stem once and forgot it. This is where I finally started understanding the true limits of my shooting abilities and quit fretting over constantly shooting those .25” groups and understood on my best day I’m really on if at 1/2” but my norm is usually at 3/4”-1” all at 100 yds. And for my type of shooting as a casual marksman I’m more than satisfied.
 
Oh I am not into that .25 MOA 5 - 10 shot BR stuff myself Jet.

Twenty shot groups with 1 MOA or less at distance is my goal, that means eliminating vertical flyers. My reloading is accomplished with basic reloading tools, budget tools even. There are just a few more steps and checks involved. I wish it was as easy to cure the wind related flyers and getting my technique consistent over a 20 shot string

I was tickled to death recently getting a 1 MOA group with my AR @ 200, AR's have always kicked my butt
 
I don't know how much force the Hornady tool applies, but based on the fulcrum principle, it will be most effective at straightening a cocked bullet if it is applied to the brass that over top of the edge of the bullet base on the high side (the side opposite the tilt direction). I would try marking the bullet high side and then moving the measuring saddle back so the thumbscrew tip is over the bullet base at the opposite side and seeing if I could get the thumbscrew to make a change in the measurement at that point that is equal to half the bullet TIR. Then measure at the bullet again to see if that fixed it.

I would also give the physics of deforming the neck alignment during seating some reconsideration. How much greater is the force involved in pulling a case over the expander than is involved in seating a bullet? We know pulling the case over the expander bends necks all the time, even when you use a lubricant in the case neck. We also know that seating pistol bullets results in obvious neck distortion when using a conventional case mouth flare. The stubby shape of the pistol bullet doesn't tend to straighten enough in contact with the seating stem, so you get that uneven bulge at the bullet base that is all on one side of the case or the other that is put there by the seating force. We know it is caused by the bullet starting into the brass crooked because going to a Lyman M-die step expander that lets the bullet sit straight up as it enters the die will eliminate the unevenness in that bulge around the case.

When I first started loading 30-06 for matches in the '80s, the 168-grain SMKs would give me up to 0.008" TIR using the standard Redding seating die. Going to their Competition seating die somewhere around '91 cut that by a factor of four. The remaining 0.002" turned out to be neck wall thickness variation, as uniforming neck walls gets most of the results into the half-thousandth range. So it follows that if changing nothing but the seating die has that much effect, then the original seating die was succeeding in pushing the bullets in crooked and at least distorting the case mouth if not pushing the whole neck off-axis.
 
In my case it was long-ish 30cal 190gr VLDs seated into 30-06 cases using a Lyman seating stem that was profiled for shorter soft-points (or possibly even a 30-30 seating stem in a 30-06 die). Felt no different than seating any other bullet to me but the results were horrible. TIR anywhere from .005"-.010"+ and patterns not groups @ 100 yards. Now I know better and use the proper seating stems for the bullets I have. That problem probably plagued me for at least a couple of weeks.

Funny thing thinking back on it, at the time I was in the practice of "straightening" the cases with the Hornady tool. There were some loaded rounds that the Hornady tool wouldn't even budge (either that or they would bend so easily I was way overdoing it). Check runout @ .008", crank the screw down until the rubber end was compressed 100% and check it again and was still @ .008"...:rolleyes: After that I gave up on "straightening" cases and used the tool solely for checking. If I can't make straight rounds there is something awry in my setup. ;)
 
Nick all I know is that I have almost eliminated runout in my ammo

Common sense tells me that when that case is fully inserted in a full length sizing die the neck and body are aligned. Any runout that occurs can only occur after the case neck and case body are not supported by the die walls

I know that eliminating the expander ball almost eliminated my runout entirely. Going with a expander mandrel also give me more control over how much compression the neck has on the bullet. I can adjust it in .0005 increments if I choose to do so. That is even more control than a bushing sizer die offers

I saw no difference in runout when seating .260 Remingtons in a Wilson Inline die using a arbor press and when the same cases and bullets seated using a .308 Win. seating die

If there is runout you can apply pressure on the high side the point where you damage the copper jacket and it will not bend that neck more than .0005 to .0015. Now that is with at least .02 or more of the bullets bearing surface inside the neck and using .003 compression. Less compression and with the bullet seated with less bearing surface inside the neck could change that. Hornady concentricity tools are cheap and anyone who wants to experiment with neck bending please buy one and let me know what you find out. Maybe I was using it incorrectly

If people want to believe that $1200 presses and $200 seating dies will eliminate their runout, more power to them. It's their money and they can spend it however they want. My method involves more prep and effort but I have seen a noticeable improvement in my groups and in my match scores and I just wanted to share it. I sure won't be reinstalling the expander bushings in my dies
 
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I'm not questioning that you are getting good results. It was just the idea there isn't enough force in seating to cause neck distortion that I thought should be reconsidered.

As to how you get a straight round, there are always multiple ways to skin the same reloading cat. Expensive equipment is one way to approach it, but it isn't the only way, especially not if you are willing to put some additional work into the loading process, as you have demonstrated. As this article shows, if you haven't put all the other ducks in a row, the right seating die can compensate for some error. But if you don't have those errors in the first place because of getting your case perfect, it's not a surprise that you don't need all the extra help.

I also agree that lots of float is the way to go with die alignment. Super-tight and rigid presses would actually be a disadvantage if you got a die whose threads and internal alignment were not concentric. I have never measured my dies with respect to that. It might be something to do.
 
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