More headspace understanding needed

Lead hammer

Lead hammer

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New Horndy brass neck sized, trimmed to 1.914", de burred, chamfered, measures 1.533".
Above brass once fired. -----------------------------------------------------measures 1.538"

I have the Hornady Headspace bushings and used D400 bushing.
As I mentioned in another post, I am loading 5 rounds to shoot as the second firing, to see is the case has finished stretching yet or not. I made a dummy round and put sharpie on the shoulder but did not notice anything. (maybe soot only works for this?) The bolt easily closes on the dummy round.

Now looking at the Saami pics, 1.5438"-.0070. What does this represent? 1.5368"
 
What i can say for myself, when i was using a headspace tool without an actual gauge to compare, it was tough to know what was my actual headspace.
Once i got headspace gauge ( forster GO gauge in my caliber), i could insert it in my tool and compare readings.
Your tool may give you a reading, but it’s a good idea to compare it with something true and consistent (headspace gauge)
 
I'm thinking that the SAAMI spec for max length is between 1.5438"-1.5368"????? My brass after firing is at 1.538" and my brass could stretch 0.0012" -0.0058" more depending on where my chamber fits in SAAMI's specs.???
 
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You are looking at the manufacture specifications for the cartridge case, meaning the maximum cartridge headspace is 1.5438" and minimum is 1.5368 for a newly made case.

And this is not chamber headspace which is minimum 1.441 and maximum 1.551. And a GO gauge would be 1.441 and NO-GO would be 1.444

The SAAMI gives you .010 (ten thousandths) between min and max headspace and to set the rifle up the preferred headspace is between 1.441 and 1.444. Meaning a new rifle has .003 between GO and NO-GO for setup to be OK.

All this means is your Hornady gauge is not calibrated to a real headspace gauge and your once fired case at 1.538" is a "comparison reading. Meaning you need a real headspace gauge to compare your 1.538" reading to and get a close chamber headspace estimate. The brass springs back after firing and if you do not feel resistance when closing the bolt the case is still shorter than the chamber.

Example below.

Below a Colt 5.56 Field gauge or max headspace at 1.4736

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Below the same gauge in my "calibrated" Hornady cartridge case headspace gauge.

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Below a fired Lake City 5.56 case in my Hornady gauge, and .006 "under" max headspace.

OJqNmQH.jpg
 
Ok, so what I have is not accurate enough to use against the SAAMI specs, only to compare between new and once/twice fired, or when my brass gets to long and I can compare the bump.
If I Sharpie the shoulder, and my shoulder was too long, would it remove the Sharpie? I assume if I loaded the dummy round several times it would show?
 
biged, illustrated what I meant to say.
You ''calibrate'' your headspace measuring tool with a gauge.
Speaking 308 here, my measurement on tool is not the same reading as it actually should, a gauge helped me know the difference.

What if you bumped every firing?
In some king of way, no matter what saami says (commercial rifles should be in spec anyways), measure fired case, bump 2 thou (bolt action), fire, repeat.
So you are in an endless cycle of 2 thou bump, 2 thou stretch, 2 thou bump, 2 thou stretch.....
 
SAAMI gives a range of dimensions... it doesn't tell you what your rifle IS... only the range it should fall in.

Like shoe size... not all size 10 shoes are the same or fit the same... but we know that they will be larger then size 9.

Size your brass for YOUR rifle... whatever that dimension is, that is the "right" dimension.

Your current FIRED case headspace is awfully close to the actual chamber dimensions. There were 60,000 reasons why that brass expanded to fill the available space. Minus spring back, you have a near mirror image of what the chamber in your rifle is. As you fire that piece of brass, it will work harden and spring back less... at some point, it simply will not and extraction will be tough... this is a bad thing.

having a body die to bump the shoulder is an excellent way to maintain proper chambering, long brass life and best fit in the chamber which can lead to best accuracy.

Jerry
 
First off thank you all for your replies.

Marty, thats what my intensions are, fire, bump, repeat. However if my once fired case was already still 0.002 off the lands, and I bumped it 0.002, well then that would suck.
Jerry, and Marty, is one firing enough to size to the chamber? I guess it confuses me when I read some shoot several times until closing the bolt is hard, then bump the shoulder back.
 
My personal case, experience is 1 year reloading rifle 1200 rounds, moderate loads as in not hot, 308.
Before buying body die from Jerry and speaking proper reload practices with him, my FLS die was bumping back 4 thou like for a semi auto.
Every firing, my brass would stretch 4 thou. I am using bolt action.
Same thing in my 2 thou bump cases, once i learned better and got proper die.

In your case, assuming you are a bolt action, test the following with a limited amount of rounds and you'll see.
Measure headspace from fired casing, this is your chamber, brass has stretched already to your chamber.
Take that measurement, remove 0.002'', this is the measurement your resized brass should be at.
Fire it again, you will see it will have stretched back to your chamber dimensions when you measure it.

Don't know for 6.5CM but .308 should be close, it doesn't take multiple firings to stretch brass. Brass fireforms quite rapidly to chamber dimensions.
Have experienced this first hand, i am not of the group of people that would neck size only. I body size every firings.

for have learned terminology myself lately, which is confusing at first, lands are where the bullet touches the rifling, not related to headspace.
I don't know the term for headspace, it's where the shoulders touch the chamber.
 
Whoops sorry Marty, I did not mean lands there, my bad. Since my first firing was a growth of 0.005", I will just use my FL die for now and bump 0.002", and make up 5 rounds. If I had more headspace length left, the 2nd time fired brass should be longer than the 0.002" growth. Maybe lol
I am loading for my Savage Stealth.

One thing I just tried is I set my calipers to .400" ( datum line for 6.5 I think what its called ) and scribed straight as I could on the Sharpied shoulder on both factory new loaded ammo, and again on the once fired. Even though its tough to be perfect measuring this way, it appears the factory rounds are in the 1.54" territory, and the once fired is in the 1.55" territory, as per the SAMMI info I posted at the start, that is at my chamber cut max length. Saw some guy on youtube do this type of measurement.
 
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Lead hammer said:
First off thank you all for your replies.

Marty, thats what my intensions are, fire, bump, repeat. However if my once fired case was already still 0.002 off the lands, and I bumped it 0.002, well then that would suck.
Jerry, and Marty, is one firing enough to size to the chamber? I guess it confuses me when I read some shoot several times until closing the bolt is hard, then bump the shoulder back.
Click to expand...

For most brands of brass under typical load pressures... YES

Case expansion has as much to do with the assembly of the action/barrel/chamber/brass as it has to do with overall load pressure. There are some situations where you can run silly high pressures with no discernable change in case dimensions (dangerous for sure but possible with todays custom stuff).

However, the average factory action has enough give in the lock up that with repeated firings, cases will expand to a point they are stiff to rechamber.

Simple test... new brass, fire it at whatever your typical load is. Eject... rechamber. Does it go in easily? Does it go in in any orientation or just one?

If it rechambers in any orientation easily, then you have a good lock up and likely, true chamber to bolt face. I would set my body die to just touch this dimension. I know the cases will chamber cause I just tested it.... now after firing any case, I size with the body die. Anything long gets a bump. I never have to worry about a sticky case.

Jerry
 
Mystic Precision said:
For most brands of brass under typical load pressures... YES

Case expansion has as much to do with the assembly of the action/barrel/chamber/brass as it has to do with overall load pressure. There are some situations where you can run silly high pressures with no discernable change in case dimensions (dangerous for sure but possible with todays custom stuff).

However, the average factory action has enough give in the lock up that with repeated firings, cases will expand to a point they are stiff to rechamber.

Simple test... new brass, fire it at whatever your typical load is. Eject... rechamber. Does it go in easily? Does it go in in any orientation or just one?

If it rechambers in any orientation easily, then you have a good lock up and likely, true chamber to bolt face. I would set my body die to just touch this dimension. I know the cases will chamber cause I just tested it.... now after firing any case, I size with the body die. Anything long gets a bump. I never have to worry about a sticky case.

Jerry
Click to expand...

Ok, I found some once fired, not cleaned or messed with brass. ( primers still in ) I took several of them and repeatedly chambered them, no troubles whatsoever. My load is 41.5 H4350 with 143 ELDx. So not super hot but decent. 2695fps, no pressure signs. excellent accuracy. This rifle is supposed to be blueprinted, maybe it's actually a good fitment.
Jerry, when FL bumping, do I take the expander rod out? I have been neck sizing, so FL size, no expander assembly, then neck size? Or does the FL die do enough of the neck when it's set up to just bump?

edit
Ok, I took the expander out, set the FL die down enough to bump 0.002", then I was worried as the neck was undersized lol, but the neck die still worked and everything seems ok except the case length grew slightly from 1.914 to 1.916. I could not get the shoulder to bump unless I set the die to touch the shell holder with the ram all the way up. Body die will be much easier if I still neck size.
 
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Mystic Precision said:
For most brands of brass under typical load pressures... YES

Case expansion has as much to do with the assembly of the action/barrel/chamber/brass as it has to do with overall load pressure. There are some situations where you can run silly high pressures with no discernable change in case dimensions (dangerous for sure but possible with todays custom stuff).

However, the average factory action has enough give in the lock up that with repeated firings, cases will expand to a point they are stiff to rechamber.

Simple test... new brass, fire it at whatever your typical load is. Eject... rechamber. Does it go in easily? Does it go in in any orientation or just one?

If it rechambers in any orientation easily, then you have a good lock up and likely, true chamber to bolt face. I would set my body die to just touch this dimension. I know the cases will chamber cause I just tested it.... now after firing any case, I size with the body die. Anything long gets a bump. I never have to worry about a sticky case.

Jerry
Click to expand...

Very good explanation.
 
Lead hammer said:
Ok, I found some once fired, not cleaned or messed with brass. ( primers still in ) I took several of them and repeatedly chambered them, no troubles whatsoever. My load is 41.5 H4350 with 143 ELDx. So not super hot but decent. 2695fps, no pressure signs. excellent accuracy. This rifle is supposed to be blueprinted, maybe it's actually a good fitment.
Jerry, when FL bumping, do I take the expander rod out? I have been neck sizing, so FL size, no expander assembly, then neck size? Or does the FL die do enough of the neck when it's set up to just bump?
edit
Ok, I took the expander out, set the FL die down enough to bump 0.002", then I was worried as the neck was undersized lol, but the neck die still worked and everything seems ok except the case length grew slightly from 1.914 to 1.916. I could not get the shoulder to bump unless I set the die to touch the shell holder with the ram all the way up. Body die will be much easier if I still neck size.
Click to expand...

Why not just purchase a body die at this point?
Really inexpensive and Jerry sells them, he could point you towards the right one
 
My plan is to buy a body die, and also buy a Lee collet neck die, ( not available yet separately??) but I’m trying to use what I have at the moment. I also see lots of people are claiming online, that setting your FL die to bump is also effective and may be better. Just not sure if they are using FL bushing dies and turning necks.
 
Myself had purchased LEE ultimate 4 die set die when i started.
Then when i learned about runout, i checked my ammo the cheap way, rolling them on a mirror.
Using my FLS die, i could see a tiny tiny amount of wobbling, which wouldn't happen when i used my collet die.
Since then i have been using body + collet combo.

And mind you, i was using a cheap FLS die (LEE), and maybe, the premium forster ones, do not produce runout.
For have recently purchased a concentricity gauge, and saw that i don't have any runout (most of my ammo is within or under 1 thou), it means my setups works for me.
Redding body die and Lee collet die are really cheap, both combined are cheaper than a premium FLS die, and do not produce runout.

I am turning necks, which have given me problems at some point, which now seems to be solved.
Edit : yes these 2 dies are available separately.
 
Thanks again Marty, the dies I am using are Redding premium 3 die set, mic seating die, standard FL die with carbide button, and neck die. It looks like most people that are using the FL die for bumping are using a Redding S bushing die, BUT it's my understanding that you then need to neck turn. With the Lee collet neck die, you don't have to neck turn do you??
 
In theory no.
My first 200 brass casings i was cycling no.
They we're FC, 15 thou thick necks, and we're very malleable.

Once I had purchased my 300 Lapua brass cases, they we're also 15 thou thick, but they we're stiffer.
At first i had to lube necks (which Lee says is not needed for their collet die) as casings could get stuck in die.
Since turning necks to 13-13.5 thou (for a factory rifle), necks glide in without lube or resistance as previous with my FC.

Brass is dry tumbled, if you wet tumble (which i used to do and sold it all), you'll need some extra process to lube or dry lube of some sort, as they will be harder to work with.

Edit : just a reminder, i am speaking 308 once again, maybe some numbers do not relate to 6.5CM that's where you'll have to do some homework.
Edit #2 : Also just read it's savage stealth, from many forum reads and from personnal experience on 2x savage model 10 rifles, Savage have got their headspace pretty tight on the GO gauge reading, due to their easy barrel installation/headspacing system.
 
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