So I measued headspace on a bunch of fired cases and... You tell me.

2aBaCa

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Ill have to (find those cases) and check. Second firing. Last time I full length sized back to my pre-fired factory ammo measurement of 1.5560. My rcbs headspace mic has factory at spec so im basically comparing it to that even if the numbers dont exactly match saami.
 
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DaveM

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New factory brass is typically a few thousandths under minimum (“0” on your micrometer) to ensure it will work in all firearms. Resizing back to “zero” on your RCBS mic will drastically reduce the life of your brass. You will see case head separations after only a few uses.

For best results, resize your fired brass no more than .003”. This is plenty of clearance in a semi-auto or a bolt rifle and will yield the best brass life and function.

The only reason to re-size your brass back to “0” on the RCBS mic is if the ammo will be used in multiple firearms with different chamber dimensions.
 

2aBaCa

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You’re measuring wrong. Spin the case in the comparator to make sure everything is squared up.
I do. Being sure everything is seated and square. Anything extreme gets further inspected.

What he said. I've never seen variations like that in my brass.
I'm going to ignore the extreme outliers as it could be I picked someone else's case or it could be from another batch of brass. (I did find a 6mm and a 260 among them which I dont own either)

semi or bolt gun?
Bolt

6.5CM
New factory brass is typically a few thousandths under minimum (“0” on your micrometer) to ensure it will work in all firearms. Resizing back to “zero” on your RCBS mic will drastically reduce the life of your brass. You will see case head separations after only a few uses.

For best results, resize your fired brass no more than .003”. This is plenty of clearance in a semi-auto or a bolt rifle and will yield the best brass life and function.

The only reason to re-size your brass back to “0” on the RCBS mic is if the ammo will be used in multiple firearms with different chamber dimensions.
I was thinking of knocking them all back to 1.5585 to cover the bulk
 
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918v

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When I measure the shoulder on my brass using a .40 S&W case I see a max total variance of .001”

Sometimes when a case gets stepped on and squished the shoulder is no longer round and you get a false reading.
 

hookedonbrass

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what lube are you using?

is the brass coming out of the sizing die easily?

sometimes if you don't have sufficient lube, and the brass is hard to pull out of the sizing die - it will actually stretch the case back out.



ignore me - i can't read
 
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FLIGHT762

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Are you depriming your fired cases before you are measuring? Fired primers will crater on the firing pin strike and give false readings.

By the looks of your measurements, that seems to be the case. Gas guns will also swipe the case head leaving burrs that will throw off measurements.
 
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2aBaCa

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Are you depriming your fired cases before you are measuring? Fired primers will crater on the firing pin strike and give false readings.

By the looks of your measurements, that seems to be the case. Gas guns will also swipe the case head leaving burrs that will throw off measurements.
Deprimed and cleaned. Careful to not measure any bur or the occasional ejector print.
 

FLIGHT762

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After re reading your measurements, I would go with what shtrRdy said. Bump to 1.558". Make a couple of dummy rounds @ 1.558" and see how they chamber. They should chamber with no effort. If so, go from there. Shouldn't be a problem.
 
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Huskydriver

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Seriously way overthinking this. Will the fired unsized brass easily chamber? If yes then don't push the shoulder back. If no then push the shoulder back .001 or .002 done
 

Huskydriver

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Next time around you will probably need to set your die in a tad more if you don't anneal as the brass work hardens and doesn't spring back as much on the down stroke
 
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Sheldon N

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Strip the bolt (firing pin, ejector plunger removed) and see how they chamber. I like to find that sweet spot right where the bolt handle drops freely on its own weight. Usually happens around 2-3 thou shoulder bump but you don't know until you check.
 

2aBaCa

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Strip the bolt (firing pin, ejector plunger removed) and see how they chamber. I like to find that sweet spot right where the bolt handle drops freely on its own weight. Usually happens around 2-3 thou shoulder bump but you don't know until you check.
My bolt takes some effort to lock close without a case. Hard to tell exactly where the extra resistance starts. I'm sure its before I can actually feel it.
 

Max

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That is what I use. Love them......

Strip the bolt (firing pin, ejector plunger removed) and see how they chamber. I like to find that sweet spot right where the bolt handle drops freely on its own weight. Usually happens around 2-3 thou shoulder bump but you don't know until you check.
That’s how I check things.......I also check my lands this way with fired brass creeping down from a bolt that won’t drop to the ever so slightest resistance to free drop. Ever so slight is where I call my lands. Measuring CBTO as I go and writing it down.
 
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Sheldon N

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Ejector and spring YES, firing pin NO. Does it cause that much resistance?
Yes, the firing pin and firing pin spring is where all the resistance comes from.

Look up the "shoelace trick" for removing the rear shroud and firing pin assembly. I don't actually use my shoelace, just a piece of cord looped around something solid that you can pull on. Just hook the cord under the sear, pull the spring back and unscrew.
 
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2aBaCa

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Yes, the firing pin and firing pin spring is where all the resistance comes from.

Look up the "shoelace trick" for removing the rear shroud and firing pin assembly. I don't actually use my shoelace, just a piece of cord looped around something solid that you can pull on. Just hook the cord under the sear, pull the spring back and unscrew.
Hmm. I'll have to try this later.

What type of calipers are you using, just curious.
A decent set of digital Mitatoyo
 

Horns8491

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I find the Hornady gauges can lead to inconsistent results.

Try this. Number some cases with a sharpie, and then measure with the Hornady. Then sort the cases and measure again, without looking at the number. The goal is to NOT know the measurement you got before for each case. Then compare the first measurement to the second. If the gauge is precise and accurate, you should get the same measurement for each case, on both the first and second try. I found that I was getting inconsistent results, even being really careful.

Then I switched to the LE Wilson micrometer to measure headspace and get precise reading to bump the shoulder back.


This gives me the same reading for a case, no matter how many times I measure it. One problem that the LE Wilson gauge eliminates is what I call "goal seeking." If you are expecting a measurement, the tendency is to fiddle with the case until the calipers show you the measurement you expected, and then call it good.

With the LE Wilson, you complete the measurement by adjusting the micrometer, and only after you've stopped turning the micrometer do you then look to read the measurement. This eliminates goal seeking. And the precise nature of the tool means you get the same reading for a case, every time.

The down side: this sucker is expensive and you have to get the LE Wilson case gauges for each cartridge. But, I think it's worth the dough at least for me.

Bottom line is this. If you arent getting accurate readings from your Hornady tool, then you are chasing ghosts trying to get exactly .002 of bump. You would be better off just using trial and error with the die. Screw it out so that lots of cases are too long and you can feel the bolt heavy to close. Screw it in a bit, and resize. Eventually you'll get to a point where all cases are resized without a heavy bolt to close, and stop there.
 
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spife7980

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^^ If you arent getting repeatable results with the hornady comaprators then you need to work on your fingers, not a new tool.

Hmm. I'll have to try this later.
For convenience on stripping the bolt, if you dont have the coin slot then just keep pressure back on the firing pin with the string until it spins freely.
 

Precision Underground

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Measuring ten thousandths is futile and will drive you nuts. Drop 3 cases of that batch and the spread looks pretty normal. Don’t over analyze it. If the bolt closes on 1.558 easily do that and move on.
 
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TheGerman

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Get a Redding Instant Indicator.

Even with the Hornady guages and a Mitoyoyo caliper, I realized I wasn't anywhere as consistant/accurate with measuring the shoulder as I thought I was. Way too much variable in the guage/caliper.

The instant indicator is amazing.
 

Horns8491

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Ya I agree with Spife. But I found that my technique was not good enough to overcome the deficiencies in the Hornady tool, so I opted for an immediate fix. I like the Redding product too but my recollection is that it doesnt work with a co-ax.
 
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Sheldon N

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No issues with my Hornady gauges here... very repeatable measurements. Apply comsistent pressure on the calipers, make sure the case is seated square on the jaws, measurements come out the same every time. I've got notes on barrel/brass headspace going back years and can still revisit those old barrels with exact same spec headpsace brass.
 
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Max

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Get a Redding Instant Indicator.

Even with the Hornady guages and a Mitoyoyo caliper, I realized I wasn't anywhere as consistant/accurate with measuring the shoulder as I thought I was. Way too much variable in the guage/caliper.

The instant indicator is amazing.
I have the same setup and have the same damn problem of my inconsistent readings. I thought it was just me.
 

Max

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^^ If you arent getting repeatable results with the hornady comaprators then you need to work on your fingers, not a new tool.


For convenience on stripping the bolt, if you dont have the coin slot then just keep pressure back on the firing pin with the string until it spins freely.
Well damn. I use a loop of paracord that I put my boot through but the coin trick is slick!
 

2aBaCa

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Yes, the firing pin and firing pin spring is where all the resistance comes from.

Look up the "shoelace trick" for removing the rear shroud and firing pin assembly. I don't actually use my shoelace, just a piece of cord looped around something solid that you can pull on. Just hook the cord under the sear, pull the spring back and unscrew.
Ok so I tried this and...
None of my once fired would fall freely on close so I started resizing.

1.5570 falls freely closed and when lowered gently.
1.5575 falls freely closed, will stop 1/4" from closed if i lower it gently but will close with almost no pressure.
1.5580 falls about 1/3 of the way.
 

Sheldon N

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Ok so I tried this and...
None of my once fired would fall freely on close so I started resizing.

1.5570 falls freely closed and when lowered gently.
1.5575 falls freely closed, will stop 1/4" from closed if i lower it gently but will close with almost no pressure.
1.5580 falls about 1/3 of the way.
Nice, so anywhere between 1.557 and 1.558 would be a good shoulder bump, depending on how easy you want the bolt to run when cycling the gun.

It's also a nice diagnostic tool, you can take one of the 1.557 pieces of brass where the bolt falls freely and see if you can "feel" the bullet touching the lands or sticking when you lift the bolt. It's another way to find exactly where the rifling lands are as the throat erodes.
 
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Huskydriver

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That's okay they are not all going to stretch to the exact dimensions. Brass grain structure and a dozen other variables play into it. I usually take 5-10 cases and then size just like described above like @Sheldon N says with the bolt falling freely on them all with my firing group removed. Whatever measurement that ends up being is what everything gets bumped to. This usually works out to about .002 but some it's as much as .004. it's in the noise. Just watch your neck tension and spring back that starts to increase after the 3rd firing usually.
 
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