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Old January 13, 2014, 01:12 PM   #1
rammerjammer
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300 win mag barrel swap, whats minimum headspace

New to the forum so Hello to all.

Just swapped the barrel on my 7 mag to 300 win mag on a Savage 110. I know case life is better with a tight Chamber, that being said I want to set my head space LESS than the .220 go gauge. I have several brands of brass none of which the belt to case head is thicker than .215 , so I don't want my headspace being say .224 which is between the go and the .227 no go. I made some beer can shims that are .0025 and set my headspace to the brass plus one shim as a go , and 2 shims as a no go. So if actual headspace is .218 would that be a problem? Im really just trying to eliminate so much unsupported case in front of the belt.

I know the possibility exits that some store bought ammo might not chamber ( i doubt it )but I will probably never shoot anything but hand loads. And I dont hunt dangerous game .this is mostly a target and deer rifle. Thanks, Mark
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Old January 13, 2014, 02:16 PM   #2
Dc777
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Beer can shims huh? Yep, your from Alabama. Lol
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Old January 13, 2014, 02:17 PM   #3
James K
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As long as the bolt closes on your ammo there is no minimum headspace. But by setting it to less than the GO gauge, you take a chance that some factory ammo will not chamber or will not chamber without excess force.

So unless you will use only your reloads or are willing to test factory loads in advance, it would be best to limit the rifle to the range.

(Note that with a belted case the belt is not intended to strengthen the case; it is at a thin part of the case. H&H intended it only to be a substitute for the rim to make feeding easier and provide case support for a cartridge with a shoulder too small for good support.)

Jim
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Old January 13, 2014, 06:42 PM   #4
rammerjammer
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Thanks, James that's what I thought. I know the short coming of the belted magnums that's why I wanted to keep head space at a minimum. Just wanted another opinion. If most brass is around .215 and you had a factory rifle that was at .227 that would be waaay more headspace than any bottle neck .
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Old January 13, 2014, 06:49 PM   #5
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.

BCS' (beer can shims) rule ! .


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Old January 13, 2014, 07:46 PM   #6
Clark
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I headspace my 7mmRM and 300WM rifles at .215" as I cannot find any brass longer than that.

SAAMI min is .220" which is hard on the brass on the first shot.
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Old January 13, 2014, 08:59 PM   #7
rammerjammer
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Clark, good to know it's worked for you im gonna go with it as is. As for the beer can shims i trust them more than the tape everyone uses.
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Old January 13, 2014, 09:41 PM   #8
Jimro
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Another option is to set your headspace to SAAMI minimum, then set up your reloading dies to bump the shoulder back 0.001" below that. Long brass life, tight chamber, and you can still use factory ammo should the need arise.

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Old January 14, 2014, 07:23 AM   #9
Bart B.
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RammerJammer, belted case life is more dependent on shoulder clearance than case headspace at the belt. It doesn't matter if the chamber headspace is .216" or .227" from the bolt face to the headspace shoulder in the chamber. As long as you full length sized fired cases such that their shoulder's set back a couple thousndths, there'll be about .003" clearance from a chambered round's shoudler to the chamber shoulder if the case head's on the bolt face. The case belt may well be several more thousandths back from the headspace ridge in the chamber.

When the firing pin strikes the primer, that drives the case forward those few thousandths such that its shoulder is driven hard into the chamber shoulder and stops there. The belt stops a few thousandths before contacting the chamber headspacing ridge; it doesn't touch it at all.

Doing this ends up putting a tiny ridge a few thousandths inch in front of the case belt but that's typically not a problem.
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Old January 14, 2014, 10:53 AM   #10
F. Guffey
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Quote:
"When the firing pin strikes the primer, that drives the case forward those few thousandths such that its shoulder is driven hard into the chamber shoulder and stops there. The belt stops a few thousandths before contacting the chamber headspacing ridge; it doesn't touch it at all"
Bart B., I would like to take you seriously but when I look thought the quote I can not see where you put much thought into your response.

I would suggest the belt be ignored and the reloader concentrate on the length of the case from the shoulder/datum to the head of the case.

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Old January 14, 2014, 12:16 PM   #11
Bart B.
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Guffey, I put more thought into it than you might think.

Doing what I suggested will eliminate the case from headspacing on its belt after its first firing and setting the fired case shoulder back a couple thousandths. After that, with a new case's shoulder clearance to the chamber being less than the new case's head clearance when first fired, the resized case will headspace on its shoulder when fired and the case belt will be a few thousandths short of contacting the chamber headspace ridge.

Some folks have been doing that for decades. It's easy to see making the right measurements in all the right places as RCBS makes its .300 Win. Mag. Precision Mic measure the case head to shoulder datum so fired cases can be compared to new or resized ones. And measuring a belted case's head to belt dimension is easy, too.

When doing all of this, the belt is ignored and the reloader concentrates on the length of the case from the shoulder/datum to the head of the case.
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Last edited by Bart B.; January 14, 2014 at 04:32 PM.
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Old January 18, 2014, 10:42 PM   #12
rammerjammer
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Ok, got to fire the new barrel today. Even with my tighter than specs .218 headspace the fired cases still stretched .015 on the first firing per my hornady headspace gauge . If I had set it with the go/no go and ended up with say a .224 headspace the brass would have stretched .021 . Now i plan to neck size until it gets snug then bump the shoulder back .002 and go again. Even though this takes the belt out of play since I will now be essentially headspacing on the shoulder, I feel I kept the initial case stretch to a minimum adding life to my brass and reducing the chances of case head seperation.
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Old January 19, 2014, 10:02 AM   #13
Bart B.
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As the head to shoulder dimenson on belted cases after their first firing is typically .001" shorter than the chamber's bolt face to shoulder dimension, I don't think it matters what the difference is between chamber headspace in the .215" to .227" range and case belt headspace is somewhere under .220". When the round fires, peak pressure pushes the case head hard against the bolt face and the case shoulder is pressed hard against the chamber shoulder; then that case dimension shrinks about.001" or so after the bullet leaves.

What was the average case head to its shoulder dimension on new, unfired cases as measured by your Hornady gauge? What was that dimension after they were first fired?
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Old January 22, 2014, 10:06 AM   #14
F. Guffey
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Quote:
Ok, got to fire the new barrel today. Even with my tighter than specs .218 headspace the fired cases still stretched .015 on the first firing per my Hornady headspace gauge . If I had set it with the go/no go and ended up with say a .224 headspace the brass would have stretched .021 . Now I plan to neck size until it gets snug then bump the shoulder back .002 and go again. Even though this takes the belt out of play since I will now be essentially head spacing on the shoulder, I feel I kept the initial case stretch to a minimum adding life to my brass and reducing the chances of case head separation.
rammerjammer, Outside of reloading but with related tools there is case forming, the initial shock of the first firing can be avoided by forming cases. Even though the person forming the cases may have no intentions of firing the formed cases. The length of the chamber can be known without leaving the shop. I form cases, the last round of forming involved a magnum wildcat, I used 8mm Remington Mag, 300 Weatherby, 300 Winchester, 300 H&H etc.. I formed all of the cases to the same length from the shoulder to the head of the case because all of the rifles have the same length chamber from the shoulder back to the head of the case.

Quote:
Now I plan to neck size until it gets snug then bump the shoulder back .002 and go again
That procedure has too many words in it to work.

Quote:
If I had set it with the go/no go and ended up with say a .224 headspace the brass would have stretched .021
http://www.saami.org/PubResources/CC...r%20Magnum.pdf

It is assumed the case stretches, a case former does not assume, they know. That is the reason they want to know what receiver and chamber. There are limiting factors on some designs and limits on belted cases.

That being said, let us start with your "brass would have stretched .021" " If in fact the difference in length between a minimum length/full length sized, factory, over the counter new case was .021" you could adjust the die off the shell holder .019", You could make the adjustment of .019" with a feeler gage. When using the feeler gage secure the die to the press with the lock nut, do not secure the lock nut to the die, and as a bonus you could verify the measurement with another leaf/feeler gage that has a thickness of .020" for tight and another leaf with a thickness of .018" for loose. I am the fan of verifying adjustments. That makes me the fan of transfers and standards.

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