Headspace Advice?


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rskent
July 10, 2011, 07:45 AM
Does anyone have any ideas of why I would be getting inconsistent case lengths?

Or maybe a better question would be how to get really consistent case lengths?

The cases are all Winchester 223 that were purchased, not picked up at the range. I am currently using a Forster bench rest sizing die and a Redding competition shell holder set. I have been using Imperial sizing wax for lubrication. I have the dies set so that the shell holder hits the die pretty hard. I would think that if you size several cases of the same manufacture, shot through the same gun, sized with same die, with the same lube, with the shell holder bumping the die (i.e. trapped in the same sized space)that you would get cases that are the same size. If it were easy, even I could do it.

I am trying to bump the shoulder back three thousands. What I am ending up with as a range of about .001 to .005. At first I thought I was having trouble with my measurements. I am using Hornady headspace comparator. I have checked out this setup using different calipers and checked out the calipers with gauge blocks. I can tell this setup is consistent and repeats to a thousandth or better.

Obviously I am missing something. Is it possible that the expander ball is pulling the case on the way out? Is there that large of a difference in Winchester cases? Do I need to anneal the cases?

Any thoughts would be greatly appreciated

Steve

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243winxb
July 10, 2011, 10:26 AM
The shoulder can move back, get shorter from head to datum line on firing. You may find that it will take 3 or more firings/ FL sizing with the same die setting for the cartridge headspace on all brass to become closer or the same length. Is it possible that the expander ball is pulling the case on the way out? Some say yes, personally i have never measured it. Lube inside the neck.

steve4102
July 10, 2011, 10:36 AM
Is it possible that the expander ball is pulling the case on the way out? Do I need to anneal the cases?

Yes, it is possible that the expander is pulling the shoulder forward.

Yes, you may have to anneal the cases. How many times have they been fired?

rg1
July 10, 2011, 11:30 AM
It takes very consistent case lubrication for consistent case headspace. Each case needs the same amount of lube, both on the body and neck plus you "have" to lubricate the inside of the necks. I've found using RCBS nylon neck brushes sprayed with Dillion's case lube works best. Polishing the expander ball also helps. I still prefer using my case lube pad for applying lube and use Dillion's case lube sprayed on the pad and on my neck brush. Lubing the inside of the neck and I prefer the brush will show most improvements.

rskent
July 10, 2011, 05:10 PM
OK I guess Iíll pick up a neck brush. I think I have some spray lube around here someplace. Iíll try polishing the expander and lubing the inside of the necks first.
If that doesnít help I guess Iíll have to look at annealing the cases.

Thanks for the insight :)

Steve

MEHavey
July 10, 2011, 05:37 PM
I also use Imperial wax, and lube each case w/ a light coating rubbed on the lower half w/ thumb/forefinger. "Charging up the finger" w/ wax usually lasts 3-4 cases, then re-wax the finger again.) :cool:

I've also found that after ~4 firings, my 308/30-06/300Win cases begin to "squeak" as the expander ball comes back through. So I then very lightly wipe a waxed finger across the mouth and -- lo & behold -- the expander ball exits smoothly and the next several cases don't "squeak." ** (somehow the ball picks up just enough on the way down to fix the problem for that case and several thereafter. `Doesn't seem to affect neck tension on seating the bullet at all.)

Try it. See if the expander ball-fix helps shoulder bump uniformity.




** (post: after 6-7 firings on the `06/300W, I re-aneal all the cases as a group once w/ Tempilaq & the cases spun w/ a drill. I pitch the M14 brass after five.)

ranger335v
July 10, 2011, 10:25 PM
"I am trying to bump the shoulder back three thousands. What I am ending up with as a range of about .001 to .005."

Brass springs back down after expanding from firing. It also springs up after sizing. And it's NOT totally consistant. Why? Not totally certain but I suspect it's due to slightly different alloy hardness in different cases even from the same box/lot that have been fired the same number of times. I've never been able to get more consistant than a 3 thou spread and 5 thou is not uncommon. Nor have I seen any target "proof" that it matters, at least not for use in factory sporters. I have not seen any evidence that inside neck lubing matters but consistancy of outside lube does and so does consistancy/rythum of both speed and pressure in operating the press.

MEHavey
July 11, 2011, 10:14 AM
Added to the occasional swipe of a waxy finger over the case mouth, I also bottom-out the case up in the die, then back off maybe a 1/4" and bottom-out the case again (thereby hitting the shoulder twice.)

Seems to work....

rcmodel
July 11, 2011, 01:09 PM
The cases are all Winchester 223 that were purchased, not picked up at the range.Unless all the cases were from the same lot#, and fired & resized the same number of times?

Some are work hardened more then others, or were harder then others from the get-go. So, some re-size easier & more then others.

Annealing might be a good idea to see if it helps.

rc

kelbro
July 12, 2011, 08:29 AM
Try removing your expander and then measure. That will tell you if you are pulling them out of whack.

Annealing will help.

Lubing the necks will help. Make sure that the lube is all cleaned out of the necks afterwards or your 'release tension' will vary. Neck tension is also very important for consistent accuracy.

fguffey
July 12, 2011, 10:52 AM
Not complicated, I have measured before and after sizing, not a habit but when I form cases by necking up there are times the case length shortens .035 thousands. There are times I form then fire to finish forming the case shortens .040 thousands. There are times the case shortens between the head of the case and shoulder, there are times when the case shortens between the shoulder/neck juncture and the mouth of the case.

Pulling the sizer ball through the neck of the case shortens the neck, necking a 30/06 case neck up to .035 Whelen shortens the neck, that must be complicated to most, most claim the neck gets thicker and or thinner as the neck is necked up or down, but, I have measured before and after.

I fire a formed case once and get once fired cases, other fire a case and get fired formed cases, and, time is a factor.

F. Guffey

fguffey
July 12, 2011, 11:14 AM
and that is for one rifle with a receiver, bolt and extractor of one design, I change receivers, bolt and extractor built with other characteristics, things change, change as when fire forming, cases can get longer ("that is some scary stuff" as Seaweed was quoted to say).

Anyhow, I determine head space first or expressed another way I determine the effect the chamber will have on a case when fired, THEN, adjust the shell holder to the die and size cases that will off set the effect the chamber will have on the case when fired. I do not know why but reloaders think it makes more sense to fire first then measure the effect the chamber had on the case, and then the tools, lots of tools, expensive tools, the first tool I reach for is the feeler gage (thickness gage), the companion tool to the press, the feeler gage, and again my favorite cases are cases fired in trashy old chambers.

F. Guffey

fguffey
July 12, 2011, 11:26 AM
Then there are those that advocate firing to form? then neck size 5 times, then start over by full length size THEN? start over, reading through this thread you find, 'the case is not fully grown until it has been fired X number + times'.

And I can not do that, start over with a case that has been fired 6 times, BECAUSE!! it has been fired 6 times. In my world the perfect case is new/unfired, then the next best is the fired once, because? of behavior, the case is predictable, but, when fired over and over and etc., I love that 'fully grown' after being hammered and hammered etc..

F. Guffey

bigedp51
July 12, 2011, 01:08 PM
rskent

I use a RCBS precision Mic and I don't think I have ever seen any cases approaching .001 variance after sizing unless I'm applying varying amounts of case lube and it migrates to the shoulder of the case.

Have you tried cleaning your resizing die and being more conservative with the case lube? I would also use a t-shirt rag and wipe the neck, shoulder and slightly below the shoulder before sizing and recheck your lengths.

You have stated you have cross checked everything and the only thing left is lube thickness on the shoulder of the case that would be the variable.

The only two other things I can think of is the possibility that the lettering stamps on the base of the case (actual flatness) extractor or ejector dings are causing different readings to occur, or the possibility of dirt and debris under the shell holder. Have you looked at the base of your cases with a magnifying glass checking for imperfections.

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