Neck Tension adjustment

[M99]

Most shooters trying to get the best accuracy for competition loads, use "Bushing" sizing dies so they can adjust their neck tension. However, we then use a separate expander Mandrel to expand the neck to the desired size because we can get these mandrels in .001 sizes.

I am asking as a question why the exact bushing in the die means much, when we are going to expand it after in any case. to set the exact inside neck diameter for bullet tension.

Can someone explain that for me please?

It would seem to be about the same situation when using an expander ball in the sizing dies since that ball is pulled through the neck after it is sized down below the desired neck diameter. My thought is that the sizing die is actually only being used to set the shoulder back and make sure the body is properly formed, and compress the neck below the proper expansion size to then allow the mandrel to expand it to the desired size.

 

[Killick]

Bingo, that’s the reason. I size my necks down .002” below my desired diameter and the neck up with my mandrel. That is per a national champion F-Class shooter. This is after I anneal then size (trim,chamfer deburr if needed) then mandrel.

 

[LCazador]

Pulling an expander through and pushing an expander through are two separate and distinct operations. I've found pulling an expander through can harm concentricity whereas this does not appear to be the case when an expander is pushed through. There is also the amount of springback that occurs when sizing with a bushing, therefore inconsistencies will occur in the amount of bullet tension when the bullet is seated. Use of the expander makes for more consistent and even bullet tension and better results on my target.

 

[quest450]

A different take here, I no longer expand necks with a mandrel just size it with a bushing
I wand to preserve the carbon build up in the neck and after sizing with a custom die there's hardly any runout so I don't wanna introduce runout by jamming a mandrel in the neck and knock off some of the lubrication I've been working hard to build up in the necks
My necks are turned with AutoDOD

 

[jepp2]

Can someone explain that for me please?

1. Yes, your sizing die reduces the neck diameter while setting the shoulder back and sizing the body, BUT I have found that more recently my sizing die reduces the neck diameter excessively. Like 6-8 thousandths below what I want the neck to be sized down to. Easy to check. Just size a piece of brass with the expander removed and measure the neck OD and compare with a loaded round.
2. Yes, you can just use the expander on the decapping rod in your die to expand the neck. But I have found that if the expander has to increase the neck diameter 0.002" or more - even when I lube the inside of the case neck and use a carbide expander - it WILL pull the neck off to the side and increase TIR of your case neck. Increasing the neck diameter by using a mandrel doesn't induce this runout.

To combat 1. I hone my die necks to the diameter they should be. Using a bushing also accomplishes a similar end point, but I find bushing dies induce more runout than a FL sizing die does with the expander removed.

And I use Lee Collet Dies with the proper size mandrel to prevent undersizing case necks and having to expand them, as well as providing case necks with less than 0.001" TIR. But some folks don't like LCD's and prefer not to use them.

 

[Eagle Six]

@jepp2 explains it well. There are different methods for different folks. Most of them settle on what gives them the best results on target. I do the same thing to establish what my specific rifle likes. I currently am using a Redding FL Type S Bushing die with SAC bushings. I don't have a way to measure tension but I can measure interference fit. Runout may be important to a certain degree. Also I'm using brass that I feel provide adequate results. TIR for case necks is .0005"-.001" and TIR for bullets is .001"-.002" and that is far better than is required to produce the less than .5 MOA I prefer. If I were a benchrest shooter I could not be happy with a standard or .5 MOA and would not only change my rifle, but may also change my brass, brass prep and that may include using @jepp2 method or including a mandrel after the bushing size, or maybe other changes.

 

[miles13]

I use Redding FL Type S Bushing dies, I never use a mandrel. I seat with a 21st Century hydro seater and get the neck tension I want, consistently.

 

[WayneShaw]

^^^^^^^ You don't use an expander of any kind with a bushing die sizer. That's why bushings are made in .001 increments. Change neck tension with a different bushing.

 

[mikecr]

I use Redding FL Type S Bushing dies, I never use a mandrel. I seat with a 21st Century hydro seater and get the neck tension I want, consistently.

You're measuring the friction it takes to upsize necks with your bullet seating.

A mandrel sets the interference desired as a pre-seating operation, and biases the neck to continue it's spring back(relieve energy) inward (instead of outward).
As far as excessively sizing all over the place, and constant annealing need that goes with that,, well I guess it's a plan. Would never be my plan.

 

[Idaho-Lefty]

The "Floating" and HIGH Up, Tapered Expander ball, in the Newer FORSTER Dies, works very "Well" for, us average reloader folks and Honing the Neck Dimension, IS a Option that, works Fine, IF you have, an Older Set of Dies.
The Bullet Concentricity ( TIR ) of, the Last couple of Forster Dies that, I bought were, LESS than,.. .002 TIR runout !
My 6 XC and, New 6.5 Creed., Rifles.. Love, the amazing, Forster Dies !

 

[M99]

Most shooters trying to get the best accuracy for competition loads, use "Bushing" sizing dies so they can adjust their neck tension. However, we then use a separate expander Mandrel to expand the neck to the desired size because we can get these mandrels in .001 sizes.

I am asking as a question why the exact bushing in the die means much, when we are going to expand it after in any case. to set the exact inside neck diameter for bullet tension.

Can someone explain that for me please?

It would seem to be about the same situation when using an expander ball in the sizing dies since that ball is pulled through the neck after it is sized down below the desired neck diameter. My thought is that the sizing die is actually only being used to set the shoulder back and make sure the body is properly formed, and compress the neck below the proper expansion size to then allow the mandrel to expand it to the desired size.

Bingo, that’s the reason. I size my necks down .002” below my desired diameter and the neck up with my mandrel. That is per a national champion F-Class shooter. This is after I anneal then size (trim,chamfer deburr if needed) then mandrel.

Thank you and the other replies. What you describe is exactly how I do it now. I have a custom sizing die that sizes the necks about .002 below what I want to end up with, and I do not use any expander ball at all. That is after Annealing. Then I use a mandrel that is the exact size I want to necks to end up at, and run them over that to get them to final neck size. I know that my loads are good, since I recently made F-Open HM using them, but am always trying to make them better. We pretty much have to score "cleans" to win matches today in F-Open at 1K.

 

[miles13]

You're measuring the friction it takes to upsize necks with your bullet seating.

A mandrel sets the interference desired as a pre-seating operation, and biases the neck to continue it's spring back(relieve energy) inward (instead of outward).
As far as excessively sizing all over the place, and constant annealing need that goes with that,, well I guess it's a plan. Would never be my plan.

ok.

 

[6Creed73]

I size down first then set neck tension with a mandrel. The main reason I like to set neck tension with the mandrel rather than a bushing is because I want the inside of the neck as smooth as possible. Using the mandrel last to set tension has the added benefit of pushing any inconsistencies in the brass to the outside.

 

[p5200]

Lot of good info here!

 

[L.Sherm]

I size down first then set neck tension with a mandrel. The main reason I like to set neck tension with the mandrel rather than a bushing is because I want the inside of the neck as smooth as possible. Using the mandrel last to set tension has the added benefit of pushing any inconsistencies in the brass to the outside.

What if you neck turn?

 

[6.5 forever]

I size down first then set neck tension with a mandrel. The main reason I like to set neck tension with the mandrel rather than a bushing is because I want the inside of the neck as smooth as possible. Using the mandrel last to set tension has the added benefit of pushing any inconsistencies in the brass to the outside.

Yup I agree.

 

[6Creed73]

What if you neck turn?

I don't neck turn, but if you do I guess you probably don't have to worry about the imperfections inside the neck.

 

[searcher]

I don't neck turn, but if you do I guess you probably don't have to worry about the imperfections inside the neck.

Even outside neck turning doesn't get it all. Those using the IDOD are probably getting the most consistent brass, thus the most consistent tension - whether using an expanding mandrel - or just using the bushing to set tension. I doubt I'd bother with a mandrel if my brass had been cut with an IDOD, especially if it was precisely annealed with an AMP annealer. Without either of those, the mandrel (with or without outside neck turning) would probably be deemed a sound method by most - even if not used.

 

[L.Sherm]

A sound method is what your groups on target show.

 

[Capt. Oblivious]

A different take here, I no longer expand necks with a mandrel just size it with a bushing
I wand to preserve the carbon build up in the neck and after sizing with a custom die there's hardly any runout so I don't wanna introduce runout by jamming a mandrel in the neck and knock off some of the lubrication I've been working hard to build up in the necks
My necks are turned with AutoDOD

Jip, once that neck comes out of the DIE nothing goes down it except a bullet