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Measuring Base to Ogive Length w/ Hornady OAL Gauge

 
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  #15  
Old 06-02-2013, 05:04 PM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Quote:
Originally Posted by woods View Post
So you're saying that if you set your FL die to size the case body and push the shoulder back, lock it down and size your cases, that there will be a "few" thousandths (in normal conversation construed to be >.002" & <.006" or so) difference between the dimension between the case head and shoulder??!!

Uhhhh in what press?
Every RCBS, Pacific and Lyman press I've full length sized cases on setting fired case shoulders back a thousandth or so average. The FL die's set so there's a few thousandths clearance between the shell holder and die's bottom at the top of the ram's stroke.

How much spread (case head to shoulder datum measured with case headspace gauges) is determined on how uniform the case lube's on the cleaned case as well as the amount of spring the press has. The type of case lube also effects the exact amount of shoulder setback in the FL die.
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  #16  
Old 06-02-2013, 06:25 PM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

It is important to headspace consistently. And I agree about the affects to this described.
But I don't agree with ogive to shoulder as a reference of measure to fiddle with.

Ultimately, with consistent HS, all that matters is the seating that produced best accuracy.
It is far easier to measure and make reference of this via casehead/boltface to ogive(OgvOAL), than ogive to shoulders.

Our ABILITIES to measure, log, & replicate, is very important with seating.
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  #17  
Old 06-02-2013, 07:20 PM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Quote:
Originally Posted by Bart B View Post
Every RCBS, Pacific and Lyman press I've full length sized cases on setting fired case shoulders back a thousandth or so average. The FL die's set so there's a few thousandths clearance between the shell holder and die's bottom at the top of the ram's stroke.

How much spread (case head to shoulder datum measured with case headspace gauges) is determined on how uniform the case lube's on the cleaned case as well as the amount of spring the press has. The type of case lube also effects the exact amount of shoulder setback in the FL die.
Odd. Instructions with dies typically say to raise the ram and adjust die down to contact with the shell holder, then lower the ram and adjust down an additional 1/4 turn for full length sizing. Creates "cam over". NO space between shell holder and bottom of die, in fact compression.

Leaving space between the shell holder and bottom of the die typically means only part of the neck is sized, the amount depends upon the amount of gap between the shell holder and die. So in full length sizing there is no gap between the shell holder and bottom of the die.

You put lube on the shoulder??!!

If the die is locked down on similar cases then the amount of takeup on the press linkages will be the same with each stroke.

I have full length sized 25, 50 or 100 cases at a time, checking the measurement between case head and shoulder datum continuously and have NEVER noticed a "few" thousandths variation, ever. Maybe .001" very occasionally (read RARELY) but never that much variation

Odd, are you really meaning this?
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  #18  
Old 06-02-2013, 10:32 PM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Great info!
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  #19  
Old 06-03-2013, 07:12 AM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

In response to my comments:

Quote:
Originally Posted by Bart B View Post
Every RCBS, Pacific and Lyman press I've full length sized cases on setting fired case shoulders back a thousandth or so average. The FL die's set so there's a few thousandths clearance between the shell holder and die's bottom at the top of the ram's stroke.

How much spread (case head to shoulder datum measured with case headspace gauges) is determined on how uniform the case lube's on the cleaned case as well as the amount of spring the press has. The type of case lube also effects the exact amount of shoulder setback in the FL die.
Woods replies:

Quote:
Originally Posted by woods View Post
Odd. Instructions with dies typically say to raise the ram and adjust die down to contact with the shell holder, then lower the ram and adjust down an additional 1/4 turn for full length sizing. Creates "cam over". NO space between shell holder and bottom of die, in fact compression.
Yup; that’s what the instructions typically say. The reason is the die company wants reloaders to full length sized fired cases enough so they’ll fit easily in the chamber of the rifle. Die companies do not know the dimensions of the fired cases reloaders use. Nor do they know the chamber headspace (bolt fact to chamber shoulder) in the rifle barrel those reloads will be used in. Full length sizing dies for bottleneck cases set in the press to “cam over” when the case is full into it typically have their shoulders set back to about SAAMI minimum case headspace. (Example; SAAMI .308 Win. case headspace = 1.627" minimum, 1.634" maximum.) If one shoots a rimless bottleneck round with too much head clearance (bolt face to case head when fired), incipient head separation is starting and, if excessive, will happen on the first firing.

Quote:
Originally Posted by woods View Post
Leaving space between the shell holder and bottom of the die typically means only part of the neck is sized, the amount depends upon the amount of gap between the shell holder and die. So in full length sizing there is no gap between the shell holder and bottom of the die.
I and most full length sizing die makers consider this a common belief as well as a popular myth. Years ago, I had a long discussion with RCBS about this very thing at a Shot Show in Las Vegas. We both agreed that FL sizing dies have less “die” headspace (bottom of shell holder to die shoulder datum when holder’s touching die bottom than SAAMI specs for GO headspace gauges. In order for your comment to be true, every fired case would have to have the same case headspace, all FL die's chambered exactly the same and all barrel chambers having the same headspace. That's not going to happen as there's a large spread in chamber headspace across all the barrels chambered for a given cartridge and a smaller one across all the die's headspace.

For example, of the several .308 Win. FL dies I have, each one set in the press with the ram/shellholder at the top and screwed down just barely snug on a .308 Win. 1.630" GO headspace gauge, FL sizing fired cases from a 1.630" headspaced chamber ends up pushing the shoulder forward a few thousandths past 1.630" case headspace. Cases so sized will not let the bolt close on them when chambered. Proof the fired case shoulder gets pushed forward as the case body gets sized down. I measured case headspace with a gauge custom made back in the ‘70's long before the Hornady LNL (old Stoney Point) case gauge and RCBS Precision Mic’s were available to do this. I use the RCBS Mic now; works great for belted magnums, too.

Backing the die up further results in FL sized case shoulders moving more forward.

Quote:
Originally Posted by woods View Post
You put lube on the shoulder??!!
Yes. Why not?

Quote:
Originally Posted by woods View Post
If the die is locked down on similar cases then the amount of takeup on the press linkages will be the same with each stroke.

I have full length sized 25, 50 or 100 cases at a time, checking the measurement between case head and shoulder datum continuously and have NEVER noticed a "few" thousandths variation, ever. Maybe .001" very occasionally (read RARELY) but never that much variation.
This is normal when the shell holder stops against the die’s bottom. More often than not, this usually sets the fired case shoulder back too far for best performance in the chamber it came out of. If the rifle’s chamber is on the long end of specs, there’ll be way too much head clearance for long case life and best accuracy. And this problem’s compounded by how much the case shoulder gets set back by firing pin impact when its fired.

And this is the reason why folks years ago used to face off the bottom of shell holders so their “height” could be made higher and end up sizing fired case shoulders not as far back using holder-to-die contact when sizing. Redding finally made shell holders in .002" height increments to do the same thing. It’s long been a practice by folks to full length size bottleneck cases setting the shoulder back 1 to 2 thousandths for best accuracy. But you’ve got to set the FL die in the press correctly to do it. Using the labels in the following link will help set the die correctly when using a case headspace gauge:

http://i860.photobucket.com/albums/a...justment-1.jpg

Quote:
Originally Posted by woods View Post
Odd, are you really meaning this?
’Tain’t odd. It’s normal. All it takes to learn exactly what happens is proper use of the right measuring tools on cases and die setup in the press then correctly interpreting the numbers. Many folks have known this for decades.

Meanwhile, I agree with mikecr; all that matters is the seating that produced best accuracy. There can be a few thousandths spread in jump distance to the lands and accuracy will rarely suffer any signifcant amount. Or, soft seat bullets in case necks so they push back a few thousandths as they contact the lands when chambered. This is often the best way to seat bullets for best accuracy; it very well centers them in the bore.

Last edited by Bart B; 06-03-2013 at 08:52 AM.
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  #20  
Old 06-04-2013, 01:50 AM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Quote:
Originally Posted by Bart B View Post

For example, of the several .308 Win. FL dies I have, each one set in the press with the ram/shellholder at the top and screwed down just barely snug on a .308 Win. 1.630" GO headspace gauge, FL sizing fired cases from a 1.630" headspaced chamber ends up pushing the shoulder forward a few thousandths past 1.630" case headspace. Cases so sized will not let the bolt close on them when chambered. Proof the fired case shoulder gets pushed forward as the case body gets sized down.

Backing the die up further results in FL sized case shoulders moving more forward.
Proves my point. Your words. A die

"screwed down just barely snug"

"ends up pushing the shoulder forward"

"past ..... case headspace"

"fired case shoulder gets pushed forward as the case body gets sized down"

SO A DIE SNUG TO THE SHELLHOLDER IS NOT ADJUSTED FAR ENOUGH DOWN TO PUSH THE SHOULDER BACK

WHERE'S THE GAP BETWEEN THE SHELL HOLDER AND BOTTOM OF DIE NOW??

Lube is to prevent the case from binding in the die, NONE NECESSARY ON THE SHOULDER
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  #21  
Old 06-04-2013, 06:04 AM
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Re: Measuring Base to Ogive Length w/ Hornady OAL Gauge

Woods, those FL dies all had a gap between their bottom and the shell holder when their shoulder was snug against the headspace gauge's shoulder; different amounts for each one. It was the spring of the press that let them move up when sizing cases so the shoulder was pushed forward. The term "press headspace" was given to me by an RCBS rep back in the 1960's referring to the distance between the shell holder bottom and die shoulder. It has a static number when the ram's at the top of its stroke without a case and a dynamic number when a lubed case is in the press. The difference between them is the amount of spring the press frame has.

If all those .308 FL dies were set so the shell holder stopped against them with the ram at the top of its stroke, all of them would push the fired case shoulder back a few thousandths and case headspace would be close to SAAMI minimum. Head clearance on the cases would be too much for best accuracy and case life. I prefer sized case headspace to be no more than 2 thousandths less than fired case headspace. So I set all my FL dies to have a few thousandths clearance to the shell holder when the press is in a dynamic condition with a lubed case in it.

To keep FL sized case headspace at the same amount after sizing, all those dies need a few thousandths clearance to the shell holder. Each one has a different dimension from the die bottom to the shoulder reference; they're just like chambers in barrels. If the shell holder bottom distance to the die shoulder could be measured, it has to be less than the desired case headspace in a static condition of the press if case headspace after sizing needs to equal or be less than fired case headspace due to the spring of the press. Same thing with my FL dies for several rimless bottleneck cartridges. This is why I mentioned the Redding competition shell holders with different heights above the standard .125" so dies could contact them and set fired case shoulders back as desired or even not at all.

Have you measured case headspace on fired rimless bottleneck cases before and after FL sizing with the shell holder stopping against the die's bottom? All of my FL dies set the shoulders back a few to several thousandths.

I tumble a few dozen decapped and cleaned cases in a foam lined tumbler with a few drops of case lube sprinkled on the foam. That uniformly lubes all the case exterior areas so the friction each has in the die is uniform and sized case headspace has a 1 to 2 thousandths spread across a batch of cases. I tried lubing only the case body decades ago, but got more consistant sized case headspace lubing cases' body, shoulder and neck.

You don't need to "shout" at me using all capital letters in your comments. It's a lot easier for everyone to read lower case letters in sentences.

Last edited by Bart B; 06-04-2013 at 06:36 AM.
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