Overall Length

[aaaBob]

Redding 308 Win FL 7W die
Hornady Headspace comparator
Mitutoyo 505-742J Dial Caliper,

What type of consistencies should
I Expect between cases?

[taylorce1]

Depends on a lot of things. What press are you using, are you using mixed brass, same headstamp differnt lots, or same headstamp brass from the same lot? There is always going to be some variation in length, just try to minimize it.

[Unclenick]

If they all have the same headstamp and the same loading and firing histories, and there are no dents that distort the case shoulders, and you aren't shooting them in a hard extracting self-loader that bends rims, then I would say that most brass off mixed forming dies should stay within ±0.001 inches. But if you have those other factors in the mix, I've seen over 0.007 inches difference in LC 30-06 brass that was fired in Garands, all coming out of the same die. For 308, probably more like 0.005 inches in that sort of circumstance. At the other extreme, I've seen ±0.0005 inches for a lote 308 Lapua brass that started new, had none of the above variables (the weight distribution let me segregate it by the tooling it was made on), and was resized on a rigid press using a Redding Competition Shell holder to get some die and shell holder contact and overload to ensure zero light gap between the two.

[hooligan1]

aaaBob, too many variables exist.
You will have the pleasure of showing us listeners what we could expect using your equipment.

[Marco Califo]

Overall Length?
Let's back up a bit here, and clarify please. Are we talking about case trim-to length? Trimming? After resizing? That would get you to uniform brass length. Is that OP's question?
Then there is overall cartridge length, after case prep, charging and seat a specific bullet, to chamber a round in your magazine and rifles chamber (two different measures).
But I have a hunch you mean something different, like run-out, or what?
Your degree of consistency is determined by you, and your reloading process.
I do have and use Redding 308 dies. Just not sure what you are asking. Specifics and correct terminology would allow us to help you better.

[Shadow9mm]

Im tinkering with this right now. Im on a hornady lock n load progressive press with hornadys dies. So far i have been within +/- 0.001. So for example the 6mm arc i am working on. The majority fall at 1.188, however i have a few here and there at 1.187 and a few at 1.189.

I have found holding the ram up for a second or so helps. Run the brass up and hold it in the die for a second or so. If you go too fast the brass springs back more. Holding it in the die lets it settle a bit.

I have heard bushing dies help. Apparently the expander ball being pulled back through can effect things a bit.

But this is all somewhat general and i am still learning.

In measuring some factory ammo, they were closer. I dont remember the exact number off hand but it was between 2 numbers. Say 1.188 and 1.887 with 7 out of 10 being at 1.188.

[Unclenick]

Marco,

The OP confused overall length (cartridge case head or "base" to bullet tip) with head-to-shoulder datum length (aka "case headspace"). That's understandable. Lots of terminology in this handloading business. When he replies next after he sees this, I will try to remember to edit the title to eliminate any confusion.


Shadow,

Good point about the expander. They certainly can pull and stretch a neck forward and off-axis. It would be best if the OP would remove his expander and then resize several and compare the head-to-shoulder length from one case to the next. The necks will be tight, but can be expanded afterward by using a Lyman M-die or by putting the expander back in the die and dipping the necks in graphite powder or motor mica to inside lube it, then running the cases back up into the die far enough to expand it (though don't be surprised if this causes some stretch or pulls the neck a little off axis, as it does when you leave the expander in the die in the first place).

[tangolima]

Originally Posted by Unclenick

(aka "case headspace").

My brass don't have headspace!

The restriction is easing up, is it not? I like it.

-TL



Sent from my SM-N960U using Tapatalk

[Marco Califo]

I thought headspace was room on a boat for a toilet.

[Nathan]

From the chamber….+/-0.0005” basically beyond caliper capability

From the sizing die of a perfected process….+/-0.001” on 20 cases measured
Perfection is about perfect lube application, press flex, state of brass anneal, length of case.

BTW, many freak out when you don’t call it CBTD measured with XX tool, bushing, etc.

Also, case wax like from Creedmoor Sports or Redding are both an easy button….go thin!

IME, Std dies have best consistency from runout and dimensional perspective, but you give up flexibility.

Also, I’ve never seen a properly setup expander pull a shoulder or neck, but I am in the minority here.

[Unclenick]

Originally Posted by Marco Califo

I thought headspace was room on a boat for a toilet.

...and room in a chamber for a cartridge case. That's the proper meaning to my mind, which is why I put the aka in parentheses. Back when all centerfire metallic cartridges had rims, "rim" was synonymous with "head," a pressure head being defined as the end cap that closes the end of a pressure cylinder. The sides of the case were considered the cylinder. So, at that point in time, headspace was literally the amount of space cut into the chamber for the rim/head to fit into, and head clearance was any excess space there was for the rim inside that headspace. When Mausers and other rimless cartridges came out, they just kept the term "headspace" for the room in the chamber for whatever surface the cartridge case stopped against when you dropped into the chamber, even though shoulder space or case space would have been more descriptive. In light of that, the reason "case headspace" makes no literal sense is that you don't qualify or disqualify a cartridge case based on how much room it has inside for another cartridge's head—or any other part of another cartridge. It doesn't need space for a head. But applying the term "headspace" to cartridge cases seems to be sticking for a lot of people, even though it appears to have come about from a misunderstanding that measuring a fired case from head to shoulder datum was an indirect or transfer measurement of the headspace of the chamber that fired it, and thus the gauge that measured the case serving as the transfer was a "headspace" gauge. You can see how that might get twisted up to be thought to be referring to the case itself. Especially when folks measured after resizing, at which point there was no longer any dimension transfer going on.

Anyway, given all the confusion, it seemed necessary to clarify I was talking about the same thing: cartridge fit in the chamber. What can cause added confusion is that Hornady refers to their gauge for finished cartridges as an Overall Length Gauge, even though it actually measures from a cartridge's head to its bullet ogive, and not the Cartridge Overall Length (COL). Nonetheless, what it measures is used to determine, indirectly, what the COL will wind up being. It just doesn't apply when you are using the cartridge case inserts to check the length from the head to the case shoulder datum (aka Cartridge Base To Datum (CBTD), and, in some schools, Cartridge Headspace), as that just determines a case dimension which is independent of the bullet length and seating depth that determine final COL.