Neck Sizing

Ambrose

I use neck sizing as a convenience. I can reload the cases immediately rather than have to go through the hassle of having to clean off the case lube by washing or tumbling. Also, I find that full length or even partial sizing causes cases to lengthen and necessitates more frequent trimming. (We all hate trimming!) But I hear reloaders say that neck sizing results in longer case life. My own experience indicates that split necks is the most common cause of case loss. Conventional neck sizing dies squeeze the neck down smaller than necessary and then the expander button expands the neck back to the necessary diameter thereby work hardening the neck and, eventually resulting in split necks. They really work no differently than FL sizing dies except they do not touch the case body--so I can't see how they can prolong case life. The Lee collet dies or the Redding bushing dies appear to me to be a different story since they squeeze the neck just enough to hold the bullet but not so much that the neck has to be expanded again. I have the Lee dies for several different cartridges but have not kept careful enough records to know if they help case life.

Any one have any experience with these dies? Or any thoughts or experience ref: neck sizing prolonging case life?

shooterone

If you just squeeze the neck just enough to hold the bullet then you are neck sizing the OUTSIDE of the neck. Being that the cases are going to be different thickness, the inside of the case neck is going to be different diameter from case to case. Which means you will have different tightness from case to bullet. Which means different presures and different velocities. That is the reason for the expander button. to resize the inside of the case neck.

dcs shooters

The Lee collet dies squeeze the neck over a mandrell, so the inside is sized and not stretched, like dragging it over expander button.

Ambrose

Judging from their price, Redding bushing dies are for the detail oriented guys who use a sorted batch of cases and neck turn them so that the cases are uniform and concentric. With those cases, sizing the OUTSIDE is the same as sizing the INSIDE. And the Lee dies, as dcs said, sizes the neck to a mandrill avoiding excessive sizing.

But, back to the point, has anyone experimented to see if neck sizing vs. FL sizing increases case life?

mrbruce

if your full length, or partial sizing is lengthening the cases you do not have them adjusted the correct way for your chamber.....
Most bushing neck sizing dies don't use a expander...

Ambrose

mrbruce; Measure the length of a fired case and then run it into your sizing die. Now measure it again. It's longer--it has to be. You reduced the diameter of the case so that material has to go some where and it results in increased length. The thing that can be accomplished by adjusting the sizing die to a specific chamber is controling headspace (head to shoulder) growth. Don't take my word for it--try the above experiment yourself.

While you're at it, with cases measured both before and after sizing, try them with and without the expander. We have read and heard that pulling the expander through the neck stretches cases. I can't measure a difference. See what you find.

And yes, bushing dies don't use an expander. That's the whole purpose behind interchangeable bushing dies; to minimize work hardening by eliminating the necessity for an expander.

"But back to the point, has anyone experimented to see if neck sizing vs. FL sizing increases case life?"

mrbruce

Ambrose--
When I run a case into my dies they do not get longer, they are shortened just enough to enter the chamber without undo pressure, thats what a FL die is designed to do, not make them longer because they are not adjusted the correct way...[:D]
Back to the point[:D]
Full length sizing a case will always be more accurate than just necksizing a case..

Ambrose

Good afternoon mrbruce,
We seem to be getting nowhere with our case length discussion. I was referring to over-all case length (head to mouth) and you are referring to head to shoulder dimension. Comparing apples to oranges.

And I take it that you have not compared neck sizing to FL sizing to see if case life is extended

bpost

quote:Originally posted by Ambrose
Good afternoon mrbruce,
We seem to be getting nowhere with our case length discussion. I was referring to over-all case length (head to mouth) and you are referring to head to shoulder dimension. Comparing apples to oranges.

And I take it that you have not compared neck sizing to FL sizing to see if case life is extended

Ambrose, Mrbruce is correct, the misunderstanding is on your part. My cases do not grow in length either. If you have a die properly set to your rifle's chamber all you are doing is reducing the case about .002 at the shoulder to fit the chamber without jamming it in. The case does not get longer after sizing I use the Redding S die with various diameter bushings to achieve about .001-.002 bullet tension when reloading the case. Neck sizing only extends case life considerably. I have fired some of my 6MM BR cases at least 12 times with no signs of fatigue. When you unnecessarily FL size the case you are removing one of the benefits of reloading.

oneoldsap

Brass wears out no matter what you do, it either work hardens or gets thin above the web or case head if you prefer. My personal experience is that neck sizing does prolong case life, especially in the smaller calibers,(7mm on down). Plus it's a lot faster and easier.

swill

Or...you could anneal the necks and continue to just necksize. It's usually necessary for me to bump the shoulder a bit after a few firings (typically 3 to 4) anyway. I never FL size for bolt guns.