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
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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