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Old August 14, 2014, 10:03 PM   #1
Metal god
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Datum to head length and head space issue

Well I thought I understood what goes on and how head space and "case" head space works but I'm a bit stumped here . As some of you know I think I'm pretty good at sizing cases to with in .001 of each other from datum to head ( case head space ) . I've been loading for one of my rifles a case head space of 1.622 and can go to 1.623 and not have the bolt hang up when closing . I've loaded well over a thousand rounds sizing my cases to this measurement with NO issues .

The other day I came across a deal to get 500 once fired brass from my range . 350 of them turned out to be LC-10 . I came home and started my extensive case prep , clean necks , clean primer pockets , uniform flash holes size and trim all to the same length . The fact I've been sizing my cases to 1.622 for a while and with two or three different manufactures . I went ahead and sized 150 of the new cases to that measurement . Well my bolt will barely close with quite a bit of resistance .

Here's the kicker . My FC brass that shows the same measurement on my comparator chambers just fine but the LC-10 brass has to be sized to 1.620 or less in order to chamber with out the bolt hanging up .

What's that all about ???

I used a Redding FL bushing die for all sized cases . At first I thought I did not have the bushing adjusted down all the way and that last little bit that does not get sized was longer jamming the case . I re-adjusted the die and sized a few more but had the same result .

I blackened the shoulder area with a marker and it seems that the shoulder is in fact bottoming out on the chambers shoulder .

please help with any ideas you think is going on here or if there is something I've done wrong .

Is the issue the two different brass manufactures and they will just have two different case head space measurements for my chamber ?

The thing that bumb's me out is I have to go bump 150 shoulders back another .002 to .003
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Old August 15, 2014, 10:36 AM   #2
F. Guffey
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http://www.saami.org/PubResources/CC...Winchester.pdf

I will assume we are talking about the 308 W.

There are gages that do not exist and at the speed we are going now we will not live long to get around to discussing them.

I am the fan of reloaders moving out ahead with new designs in tools. When I go help someone in our small circle of reloaders I bring my own dies. And! lube, I do not insist on being popular because I agree, if disagreeing upsets someone, they will be upset.

You are measuring from the datum/shoulder to the head of the case. You have not listed the distance from the datum/shoulder of the chamber to the bolt face. The first measurement I make is from the shoulder of the chamber to the bolt face. I do not have a head space for everything, my chamber has a head space length from the datum to the bolt face. my cases just have a length, that length is from the shoulder/datum to the case head. Nothing complicated about that, I have one standard, one measurement. After that everything else is compared to the standard.

Chamber gages, for me? not a problem. I have new barrels, take off barrels and I have worn out barrels, I do not need tomato stakes (cute saying) I do use chambers as gages, I can use the chamber from a new barrel, a take off barrel and I cut chambers off of worn barrels to save room.

there is an insistence a case is sized when the firing pin strikes the primer, big deal, if a case can be sized with the powerful firing pin it can be sized with a hammer, place the case in a chamber gage, hit the case head with the hammer (no primer, bullet or powder) and like magic the case will be formed to the chamber, do not forget to lube the gage if the case is to be removed.

I have used an arbor press, I have used round punches when checking Wilson case gages. the only reason for driving the case into the chamber or gage is to determine diameter.

If I was having your problem I would shim the case off the deck of the shell holder with a feeler gage, believe it or not, shimming the case off the deck of the shell holder reduces the length of the case from the shoulder to the head of the case and all of the diameters in thousands from the case body/shoulder juncture to the case head/case body juncture.

Problem, measuring the diameters. Feeler gages come in various thickness, some refer to the feeler gage as thickness gages.

F. Guffey

Last edited by F. Guffey; August 15, 2014 at 10:38 AM. Reason: remove 4
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Old August 15, 2014, 11:11 AM   #3
mehavey
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Not headspace, but base/web area diameter if fired from a machine gun.
See if you can scrounge up a small-base die and find out if that does it.
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Old August 15, 2014, 11:16 AM   #4
Brian Pfleuger
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Quote:
Not headspace, but base/web area diameter if fired from a machine gun.
See if you can scrounge up a small-base die and find out if that does it.
Yep. That extra 0.002 isn't about the shoulder, it's about the lower body of the case.
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Old August 15, 2014, 11:28 AM   #5
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sorry , yes this is a 308 Win

Quote:
You have not listed the distance from the datum/shoulder of the chamber to the bolt face.
right or wrong , the way I got my head space length was by measuring a case( neck sized only ) then fired from the rifle . I had a sticky bolt lift and could barely chamber the fire formed case ( very hard to close the bolt ) I measured five of these cases and came up with a head space of 1.6245.

I think what my real confusion is . It's the fact I have never had to size a case for this rifle as short as 1.620 in order for it to chamber freely . What I'd like to know is what has changed ? What am I doing different or what is going on with the components that is different ?

Quote:
If I was having your problem I would shim the case off the deck of the shell holder with a feeler gage, believe it or not, shimming the case off the deck of the shell holder reduces the length of the case from the shoulder to the head of the case
you mean like this

I've been doing this since you recommended it to me months ago . It is the very reason I can size all my cases to just about the exact same size , Thank you for that

I do know how to correct the problem . What I'm trying to figure out is why I have the problem
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Old August 15, 2014, 12:04 PM   #6
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What I'm trying to figure out is why I have the problem
The cases were fired either in a machine-gun, in a gun with a very generous chamber or possibly significantly over-charged. MG seems most likely.
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Old August 15, 2014, 12:28 PM   #7
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I'm confused about your .308 Win case headspace measurements. Having never measured a fired one outside of 1.629" to 1.635", your numbers below SAAMI new minimum case headspace of 1.627", something's out of kilter if you get readings below that.

What are you using to measure case headspace?

How did you calibrate it so it'll read 1.630" if you measured a GO headspace gauge?
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Old August 15, 2014, 12:34 PM   #8
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I was thinking that same thing but the diameter of the cases seem to be the same from cases that chamber fine and ones that don't , at all areas of the cases .

Here's a pic that seems to show the cases hitting the chamber shoulder and no real scraping along the body .


Direct link to click and zoom WAY in
http://imageshack.com/a/img909/3659/3Du1S6.jpg
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Old August 15, 2014, 12:44 PM   #9
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This case was loaded 5 times and fired from the same rifle every time . The last loading was hot resulting in a sticky heavy bolt lift . That case is in the pic below .
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Old August 15, 2014, 01:06 PM   #10
Bart B.
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Corrected instructions

I'd borrow a .308 Win GO headspace gauge, put the gauge on it then zero the caliper on that headspace gauge. Then measure fired and sized cases with it to see their difference from the 1.6300" standard the headspace gauge has.

Last edited by Bart B.; August 15, 2014 at 03:37 PM.
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Old August 15, 2014, 01:31 PM   #11
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I will throw my 2 c worth in here.

Using a collet case length cutter, I run into the same thing.

You would think once you set the COAL, it would work very close each time.

On the one I was given (fortunately I did not pay for it) some came out way short when done, had to keep repeating checking which was a pain.

The Little Crow Gun works drill cutter that indexes off the shoulder, always has it within the right range (not perfect but it average right around the cut to length).

So, how can the collet COAL cutter now work? Obviously the web thickens is a factor, but its a COAL measurement, no matter what change when its set at xxxx.xx it should quit cutting.

Seems like this is one of those but not a clue as to why.
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Old August 15, 2014, 01:39 PM   #12
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Quote:
the way I got my head space length was by measuring a case( neck sized only ) then fired from the rifle .
I had a sticky bolt lift and could barely chamber the fire formed case ( very hard to close the bolt )
I measured five of these cases and came up with a head space of 1.6245.
What tool are you using to measure this distance [1.6245"] with? Some kind of commercial/homemade comparitor?
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Old August 15, 2014, 02:07 PM   #13
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Measured using the comparator in pic above

I just ordered a Forster headspace go gage . Should be here early next week .
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Old August 15, 2014, 02:50 PM   #14
Bart B.
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Do you zero that digital caliper on a fired case each time before you use it?

What's the label on that silver colored gauge in the red holder clamped onto the caliper jaw?

I ask because Hornady's instructions says "Most handloaders prefer to'zero' the caliper's indicator on the longest fire formed case." That reading is usually the reference and will read.001" to .002" less or more on sized cases. All of which is why I'm not understanding where your posted reading's are coming from.

I corrected my earlier post on the headspace gauge. Using it will be a good standard to base your other measurements against. If it chambers easily in your chambers, they are at least 1.630" in headspace; fired cases are typically .001" less than chamber headspace.

Last edited by Bart B.; August 15, 2014 at 03:41 PM.
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Old August 15, 2014, 03:36 PM   #15
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No I don't zero it every time I use them but do zero it each time I pull them out to use . While in continues use I close them often to make sure they are still zeroed .

The # is D400
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Old August 15, 2014, 07:06 PM   #16
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Two of my buddies and I use the Hornady bushing headspace gauge and none of them match up to each other. Mine is the oldest and heavily used by far and mine has the greatest difference in readings. So my feeling is that the Hornaday gauge is not an absolute compared to a spec. It's fine if you use on it on your brass, and on your press and always using the same gauge bushing.

Sinclair makes the same inserts out of stainless steel.

Just something to consider.
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Old August 15, 2014, 07:34 PM   #17
243winxb
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Bolt face not square to the chamber?

The LC-10 brass may have been fired in a rifle where the bolt face is not square to the chamber. Thats my guess.
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Old August 16, 2014, 08:11 AM   #18
F. Guffey
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Quote:
The LC-10 brass may have been fired in a rifle where the bolt face is not square to the chamber. Thats my guess.
If I was guessing I would guess the case would be leaning if the case body was not square with the case head, out side of reloading there is a tool designed to check for leaning anything.

F. Guffey

Last edited by F. Guffey; August 16, 2014 at 08:35 AM. Reason: change put to out
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Old August 16, 2014, 08:24 AM   #19
F. Guffey
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Quote:
you mean like this
Yes, after raising the deck height with the feeler gage make sure the die is contacting the shell holder. If the die is not contacting the shell holder the case has more resistance to sizing than the press can overcome.

Case head preventing chambering? Remember the bottom .125" can not be sized because of the deck height of the shell holder then a reloader should add the radius at the opening of the die. It is possible to go up to as much as .012: when using a RCBS shell holder. For me I can not miss, I use the feeler gages to size cases for short chamber, it woks. The same could be said for sizing long cases for standard cases.

Length of the chamber from the shoulder to the bolt face. I am the fan of zero.
I do not have a zero for the chamber length, I do not have a zero for the case length, I have one for both, that leaves me with + and or -.

I have suggested the reloader use the die as a gage for the diameter of the case head. All of my case heads can be checked with a Wilson case gage because the Wilson case gage is generous. Most of my case heads will fit into a full length sizing die, when checking case head diameters I am looking for upset case heads, OR! full length sizing dies that could double as a small base die.

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Old August 16, 2014, 09:42 AM   #20
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Quote:
fired in a rifle where the bolt face is not square to the chamber...
Interesting... and one that fits all the symptoms.

EZ to prove out as well.

- Size one to chamber (whatever dimension req'd)
- Fire it (thereby squaring op the head again)
- Confirm that the case will now fit when sized to "normal" dimensions

Rocket science at its best.
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Old August 16, 2014, 01:23 PM   #21
Bart B.
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Goodness, mehavey, that's interesting.

I've never seen an out of square case head square up when fired in the chamber whose out of square bolt face unsquared it the first time. But they tend to square up after a couple firings with a squared up bolt face behind them.
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Old August 16, 2014, 05:21 PM   #22
mehavey
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Quote:
when fired in the chamber whose out of square bolt face unsquared it the first time...
We're talking the (probable machine-gun fired) LC brass. Did I miss that the OP had
subsequently fired it in his own rifle and it then still failed to size to common dimensions?
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Old August 16, 2014, 09:29 PM   #23
Metal god
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No nothing missed . I've been talking about once fired LC-10 brass I bought from my range . I have not shot any of it .

Although I've been using feeler gages when sizing brass . They all have been .001 to .0025 . I never thought about lifting it up as far as I could in the shell holder like Guffey says . That sounds like a good idea . I'll need to adjust the die but that will size the case closer to the head . I'll give that a try tonight .
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Old August 16, 2014, 10:41 PM   #24
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Don't sweat the feeler gauge just yet. That's for sizing to a known dimension "less than "lull length."
Since you are already using the Hornady comparitor, you are sizing to an exact dimension, not a ram gap..

See if a firing results in a normal sizing operation next time around.
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Old August 17, 2014, 08:11 AM   #25
Bart B.
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'Tis my opinion feeler gauges are used to size fired .308 cases enough that their headspace is less than the SAAMI minimum of 1.627".

If you compare a full length sizing die to the chamber end of a barrel, they both have a dimension from their shoulder to where the case head is when the case is under pressure. Bolt face behind the barrel's chamber, shellholder face below the die's chamber. A barrel chamber's headspace at GO gauge minimum (with the barrel hard against the receiver) is 1.630". Virtually all full length sizing die's minimum dimension (with the die hard against the shellholder) from its shoulder to the shellholder face is several thousandths less than 1.630"; usually about 1.625" so after case body and neck springback happens, the sized case headspace is at industry minimum. It will be more or less depending on die and shellholder tolerances.

My Forster GO gauge head sticks out of my RCBS .308 FL die bottoms .129" to .135". Some were bought at gun shows and had their bottoms ground back a little. A Lyman FL die in new condition has the gauge head .138" past its bottom. If it's set in the press to be hard against the shellholder at the top of its stroke, cases are sized too much and have about 1.622" headspace. Way too short for safety.

All of which means the much-used way of setting a die to touch a raised shellholder then screw it down .018" (1/4th turn) can end up sizing fired cases way too much. Use a GO headspace gauge with a caliper to measure its head protrusion from a die's bottom. If it's more than .130", that die will probably full length size fired cases too much for safety. The proper use of a case headspace gauge will help you set the die in the press so fired case headspace is set back only a few thousandths of an inch, 1 to 2 for bolt action rifles, 3 to 4 for semiautos and lever actions.
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