Sorting Brass By Neck Thickness

[nick338]

To start this is not a bench rest related question. Simply looking for info from anyone that sorts brass by measuring neck thickness for shooting at 600 and beyond. I don't turn necks and typically order a no turn chamber, but I'm interested to hear if sorting by thickness will have any impact on fliers, vertical or ES, SD outliers, and if so, what is your range of acceptance.

I used the Redding neck thickness gauge to check a bunch of Lapua .308 cases and roughly half of them would have a variance of .00075 or less and the rest would come in around anywhere from .001 - .0015. Is this enough to matter?

 

[morning would]

No. If you order no turns, I wouldn’t sweat it. It’s as bad as weighing brass thinking it helps imho. If you want to focus on something neck related, focus on neck tension. But I am starting to think that’s not as important as I once thought it was. Though nothing is conclusive just yet.

 

[nick338]

Neck tension and brass thickness are related so that's why I'm inquiring. I can tell the difference when I mandrel brass to set tension that some of them do not feel the same.

 

[straightshooter1]

To start this is not a bench rest related question. Simply looking for info from anyone that sorts brass by measuring neck thickness for shooting at 600 and beyond. I don't turn necks and typically order a no turn chamber, but I'm interested to hear if sorting by thickness will have any impact on fliers, vertical or ES, SD outliers, and if so, what is your range of acceptance.

I used the Redding neck thickness gauge to check a bunch of Lapua .308 cases and roughly half of them would have a variance of .00075 or less and the rest would come in around anywhere from .001 - .0015. Is this enough to matter?

I've measured many many brass neck, not only Lapua but other brands that have way more variance than Lapua necks. Given the "variance" in any of them, it's just not going to have any measurable effect on velocity ES or SD's. . . especially when a bullet is seated in them. Variance in case volume is something much more relevant to ES's and SD's, and "flyers". Because it's a lot of work to measure and sort case volumes, sorting by case weight is done since there is some correlation between case weight and case volume due to variances in case head thicknesses where most of this variance comes from.

Where neck thickness variance comes into play is with "neck tension" and the variance in when blowby happens as the bullet it being released. While these two things can be mitigated to some extent by way of sorting, it's such a small thing that it's not really even measurable by equipment that any of us typically have. I'd say a more effective method would be to run a mandrel through the reduced necks to move some of those variances that effect neck ID's to the outside or use a collet neck sizing die to squeeze and size the neck around a mandrel. The squeezing effect tends to cause the brass to flow a little (like squeezing clay in your hand) resulting is a little less variance in neck thickness within a neck (how much it happens depends on the hardness of the necks).

Anyway . . . take this as some food for thought.

 

[nick338]

I do sort cases by weight for anything out to 600 and beyond if I'm looking at group sizes. I don't have the patience to sort by actual volume.

 

[straightshooter1]

<snip>
I don't have the patience to sort by actual volume.

LOL . . . who does?

 

[Baron23]

LOL . . . who does?

BR guys maybe?