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Old November 3, 2013, 11:55 AM   #26
tangolima
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I simply don't let the rim to headspace in my SMLEs. I only partial length resize the brass after the first shot, so that the cartridge is always headspaced by the shoulder, instead of the rim. I just retired a batch of .303 Brit brass after no less than 20 firings. So why do we worry about rim thickness?

-TL
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Old November 3, 2013, 04:39 PM   #27
wogpotter
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Because that's where headspace is measured on a rimmed case such as the .303. There are 2 separate & distinct, but interconnected problems here & to get the best results we need to fix any problem with both of them.

Let me try & explain differently. Take a look at these 4 "cases"



Top is the whole ding, dang doodle loaded round, lets assume its all within spec & works as we're going to use it a a reference.

It breaks into 2 sections, the rim, which is also the headspace, & the body, which is the chamber dimensions. (we're assuming a fired neck resized case for the sake of argument.)

Now lets have some excessive headspace, but with a normal chamber. What happens?

Well the normal body is pushed forwards by the excessive headspace, so to fix the problem we need to fix the cause of it, the headspace. If we fix the headspace by changing the (perfectly good) chamber dimensions we've just compounded the error.

Lets look at the other problem, "generous chamber".

Its the wrong length & size in the body of the case, but the rim (where we headspace) is fine. Can we fix this with headspacing? Nope, this is where we fix the chamber dimensions to be correct.

So what's the "right" way?

Step 1: Fix any headspace issues by changing the bolt head. Why? well, because if we can't hold the rim in place everything else is moving with it causing all sorts of false readings.

Step 2: Now we KNOW the headspace is correct & the round is immobilized we can see (for the first time) how much of the problem is headspace & the case flopping back & forth & how much is an over sized chamber.

OK, so what does this do for us?

It works the brass less.

It is more consistent, because its always in the same place (don't forget the bullet is moving back & forth as well, changing the jump to the lands)!

It fixes the 2 problems independently, actually fixing the problems instead of coming up with a "fix" that just hides them.
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Old November 3, 2013, 04:47 PM   #28
wogpotter
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If you're getting 20 reloads then keep on doing exactly what you're doing because you're doing something right!
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Old November 3, 2013, 05:32 PM   #29
chiefr
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I have been using PPU brass in 8-lebel, 6&7 Carcanos, 7x53, 7&6 Jap, 303Br, and 8x57. For some milsurps, PPU is all you can find.
Over several years of using their brass, I find it far superior to all domestic brass and almost as good as Norma and Lapua, especially when case life is important. I find it does not stretch much.

I think one poster already mentioned the problem with generous chamber dimensions so common in Brit surp rifles. The only way one can get decent case life is to NSO and dedicate their brass to a specific rifle. I know first hand this can be a PITA if you have more than one 303.
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Old November 4, 2013, 10:06 AM   #30
F. Guffey
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Quote:
head space is the length of the chamber

I disagree.

Wogpotter, I do not trust you, I question your motives.

What purpose are you serving when you omit:

"from the datum to the bolt face".

Head space is the length of the chamber from the datum/shoulder to the bolt face.

Before the Internet, any one that purchased a catalog from Santa Fe Arms received, in the catalog, a glossary of terms, my catalogs from Santa Fe Arms were published in the mid 50s. Back then a case did not have head space. Included in the glossary of terms covering head space they included head space as it applied to the belt and rim.

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Old November 4, 2013, 10:37 AM   #31
F. Guffey
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“So why do we worry about rim thickness?”

From post#12 Mike40-11,

“I have also had case head separations with S&B, even S&B factory loads. Twice! Happened in one day with one batch but, still, I won't even bother reloading it”

Reloaders are happy with suppliers that do not offer options, not me, problem, I want cases that do not fit, I want cases that are too long, I want cases with thick rims, I want belted cases that are long from the front of the belt to the case head. About the the time it was too late, R-P offered cylinder brass, a 30/06 type case with a 35 Whelen head stamp with a straight wall, the case was 2.650 long from the mouth of the case to the head of the case. HOW COULD A RELOADER MISS?!!

Just an observation but I believe suppliers would have trouble finding reloaders that would know how to take advantage of the added material. I have purchased cases from shooting ranges. Before purchasing I have measure the cases for length from the shoulder to the head of the case, WHY? I was looking for cases that had been fired in trashy old chamber that were long from the shoulder to the bolt face as in chambers with excessive head space.

http://www.z-hat.com/Cylinder.htm

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Old November 4, 2013, 12:09 PM   #32
wogpotter
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Quote:
Wogpotter, I do not trust you, I question your motives.
I omitted exactly nothing, I simply disagree with you & it was your post I was quoting word for word.
Here is the entire paragraph. I have underlined the part I quoted.

Quote:
I have no ideal what you know, head space is the length of the chamber, it is a ‘from’-‘to’ concept as in from A to B. I have no ideal what you know, but, if I had the chamber that caused case head separation with new ammo I would ignore the rim and form cases that seated against the shoulder of the chamber and bolt face. Chamber shape, in the beginning the belt and or rim held the case to the rear, problem, in the beginning the case had a lot of taper, things did not get much better when it got to the shoulder, meaning P.O, Ackley was the best thing that ever happened to old cases with long tapers.
I have no motive except to stop the spread of incorrect information on reloading forums.

If you were to say "Some cases have head space measured from the case rear to the datum line & others are measured differently, from the front to the back of the rim exclusively" I'd not be disagreeing with you. Nor would SAAMI, the British War Office & the European equivalent of SAAMI!
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