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Pulling bullets / Reseating / Neck Tension

 
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  #15  
Old 05-29-2013, 03:23 PM
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Re: Pulling bullets / Reseating / Neck Tension

Quote:
Originally Posted by X-man View Post
I don't think case neck spring back has much to do with case hardness.
Sure it does, you only need to examine the test for validity.

Quote:
Originally Posted by X-man View Post
benchresters used to turn their brass (tight neck chamber) so they didn't have to re-size the neck until they needed to move the shoulder back. I know for a fact the case neck is a lot harder after 5 plus firings yet the neck spring back was the same.
How do you know the case necks were 'harder'? I personally doubt it.
I currently run with tight clearances on a couple cartridges(one is fitted), and I also measure seating forces with an instrumented mandrel. What I see is that necks that do not require neck sizing to reload(they spring right back to dimension), never change in hardness.

Quote:
Originally Posted by X-man View Post
What tends to complicate the issue is the neck thicken over several firings and this will start creating different spring back until the necks are turned back to spec.
Necks do not thicken with firing, but with your FL sizing.
Stop FL sizing, and necks remain stable in thickness. No donuts forming, no reaming needed, and no more trimming.
I've burned out a couple barrels now with a small lot of brass(>30 reloads) and my originally turned necks have never changed a bit. This in 6.5WSSM. I've never had to re-turn necks in 223, 6br, or 6xc either.
It's because I don't ever FL size.

How do I do this when seemingly everyone says I have to FL size?
They're wrong.

Last edited by Mikecr; 05-29-2013 at 05:44 PM.
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  #16  
Old 05-29-2013, 07:59 PM
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Re: Pulling bullets / Reseating / Neck Tension

Quote:
Originally Posted by Mikecr View Post
It's because I don't ever FL size.

How do I do this when seemingly everyone says I have to FL size?
They're wrong.
Mike,
Do you ever have to bump shoulders back? How do you avoid having to do that? Sorry if it was in one of your post and I missed it.
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  #17  
Old 05-29-2013, 08:48 PM
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Re: Pulling bullets / Reseating / Neck Tension

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Originally Posted by Mikecr View Post
Now once you size down the normal neck to ~1-2thou under cal, you have completed one hardening cycle, and the case neck should spring back outward from whatever sizing needed to leave you with ~1-2thou under. It's typical to need 3-4thou under cal worth of sizing to be left with 1-2thou under cal after springback.
If you sized down more than 3-4thou under cal, you should expand necks to cal, leaving 1-2thou under after springback(inward). No good in going overbored, and bushings can only produce predictable result with 5thou or less of sizing.
So if you want .003" bullet grip with a Lee Collet or a bushing then you size down to .004" below and it will springback to .025" to .003" under caliber

But with an expander ball you want an expander that is .001" below caliber and it will springback in to .025" or .003" bullet grip

Or will springback only occur with the expander ball since you are sizing both way, down and back up?
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  #18  
Old 05-29-2013, 10:15 PM
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Re: Pulling bullets / Reseating / Neck Tension

Found this post by boomtube which may add some information and understanding on this topic:

Neck tension-- how much ???


"Basically, Mikecr is absolutly correct, "best" "tension" is 1 to 1.5 thou. In fact, it isn't physically possible to even have more than about 1.5thou.

What most people call "tension" isn't. What they mean is how much smaller the neck ID is than the bullet, that's what machinests call an "interference fit", a jam-fit actually. Tension is NOT properly the amount of force needed to jam the bullet in, it's really the amount of pull required to take it back out.

Our cases have enough elasticity, or spring, in them to allow them to retain a springyness that holds the bullets in place. But, if it's stretched too far the elastic of limit of the brass is exceeded and it just permantly stretches/expands. (That's what happens when we fire the rounds, the neck is "permanently" stretched too large to hold another bullet until we "permanently" squeeze it back smaller.)

The elastic limit of common case neck brass is about 1 - 1.5 thou, rarely as much as 2 thou (it does vary a little by the physical size of the neck). If your .338 neck was sized and ball expanded to .330 your bullets will have to stretch it to .338 during seating. That much difference requires a noticible force to push them in and some feel that means it will hold the bullets tighter; it doesn't. You can prove that by seating, measuring the neck diameter, pulling the bullet and measureing it again; it will likely spring back only 1-2 thou from loaded diameter. Proving that no matter the neck diameter before seating, the permanent difference will only be 1 or 2 thousants (depending somewhat on how and where the measurements are taken and the original diameter of course). Thus, we can permanatly expand with an expander OR with a bullet but the end tension will be the same in either instance. There is no bullet tension value to expanding a neck to less than about 2 thou under bullet diameter.

One significant factor in having lower seating tension (in your case that would ideally mean an expander of .336"- .337") is that less force needed to push the bullets in so they will enter more easily and, from that, tend to go in straighter.

One rarely understood value of the Lee collet neck sizer die is it frequently achieves a proper REAL bullet tension fit. "
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  #19  
Old 05-30-2013, 02:23 AM
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Re: Pulling bullets / Reseating / Neck Tension

Quote:
Originally Posted by X-man View Post
I don't think case neck spring back has much to do with case hardness.

The reason I think this is back in the day some benchresters used to turn their brass (tight neck chamber) so they didn't have to re-size the neck until they needed to move the shoulder back. I know for a fact the case neck is a lot harder after 5 plus firings yet the neck spring back was the same.

What tends to complicate the issue is the neck thicken over several firings and this will start creating different spring back until the necks are turned back to spec. If I remember right the spec was 1-1.5 thou over all...very tight! Rifles set up this way shot well enough, but the slightest bit of carbon or whatever in the neck area caused significant fliers and pressure spikes.

I never re size brass after pulling a bullet.
I got out of BR just after Lapua brass arrived so most of my experience was shooting the old
Sako 220 Russian brass. I had one of those BR rifles your posting about back in them days we called them zero neck clearance. My Henriksen reamer came from Lester Bruno when he was back east and there was few like Speedy,Hammond,Jones etc making shoulder bumping dies.

The standard tight neck at that time was .262 few were at .260 zero clearance start about .258 and pretty thin necks. I don't remember the necks getting harder as much as trying to keep the necks and the chamber clean. I know lot won't shoot them for that reason and after shooting one I had to agree.

I've still have some Sako 220 Russian brass and primer pocket bushed by Skip Otto and there for a .262 neck 6ppc. I'm little over 30 firing on each cases never been annealed they lost little spring back not much.

I'm not posting this to agree/disagree with anyone just kind of nice that someone remembers those old BR rifles.
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  #20  
Old 05-30-2013, 11:15 AM
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Re: Pulling bullets / Reseating / Neck Tension

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Originally Posted by 375fan View Post
Mike, Do you ever have to bump shoulders back? How do you avoid having to do that?
The steepest shoulder angle I'm running right now is 35deg. With this, I do eventually have to bump shoulders, and forever more once I do.
But shoulder bumping in itself is nothing like FL sizing.

FL sizing begins near the webs and works it's way up a case as it enters further in the die. It's like squeezing a toothpaste tube, moving brass up toward/into the necks, lengthening them, causing a need to trim. FL sizing is re-forming.
Shoulder bumping with ~30deg and better angles, does not roll brass, it just pushes it inward.

The reason cartridges with low shoulder angles and high body tapers grow so much in firing(even with tight headspace), is wedging, as THIS chamber presents no hard stopping point for case dimensions. A perfect example of such a terrible design(w/resp to reloading) is the 30-06.
'Improved' cartridge really means improved over any 30-06 baseline design(ex; 243Win to 243AI, or 6XC, etc). These are easier to hold in a stable performing condition, reload after reload.
Something like a 30-06, 270, etc, grows on each firing, and has to be FL sized to rechamber(not just bumped).

WOODS:. Springback always occurs opposite the last action. It doesn't all occur at once though, but maybe 85% of it right away. The rest occurs further in the springback direction -over time. Springback happens everywhere brass is squeezed or expanded including primer pockets.
So for hunting ammo, I let sized/primed brass set for 2wks before testing/setting seating forces, resetting primer crush, and loading. Then I test a sample of this to be sure I'm right for the trip.
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  #21  
Old 06-02-2013, 03:42 AM
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Re: Pulling bullets / Reseating / Neck Tension

Quote:
Originally Posted by Mikecr View Post
Sure it does, you only need to examine the test for validity.


How do you know the case necks were 'harder'? I personally doubt it.
I currently run with tight clearances on a couple cartridges(one is fitted), and I also measure seating forces with an instrumented mandrel. What I see is that necks that do not require neck sizing to reload(they spring right back to dimension), never change in hardness.

Necks do not thicken with firing, but with your FL sizing.
Stop FL sizing, and necks remain stable in thickness. No donuts forming, no reaming needed, and no more trimming.
I've burned out a couple barrels now with a small lot of brass(>30 reloads) and my originally turned necks have never changed a bit. This in 6.5WSSM. I've never had to re-turn necks in 223, 6br, or 6xc either.
It's because I don't ever FL size.

How do I do this when seemingly everyone says I have to FL size?
They're wrong.
How can brass not work harden after each firing? The neck expands to the chamber and then retracts to what you see....Unless your chamber is set up for a zero sizing, but we aren't talking about that here.

So your brass does not flow....Ever?

I have a K&M inline seater with the "force gauge" (somewhat accurate) and also a custom built seater with a piezo sensor (extremely accurate) to measure the bullet seating force.
You are suggesting you never saw any difference in 40 firings?
You put over 40 firings on a case and never had to touch the necks it in that entire time?
Can I assume that since your brass doesn't work harden you never had to anneal them either?
I must be misunderstanding you?


I did not start out FL sizing everything.
I notice an consistent accuracy improvement when I started Fl sizing in my 6mmbr so I made a few phone calls to Bruce Baer, George Gardner, and a few other of the top gunsmiths around an asked their input. If you have a problem with that talk to them and tell them how to do it right...

This is Long Range Hunting and we don't run chambers that tight because the guns stop working. I have been to a few Sniper's Hide Cups (didn't make this year) and the field is full of guys with precise rifles that wont run. Are you suggesting otherwise to the OP?
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