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Old July 30, 2016, 05:57 AM   #1
Duncan74
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What is the proper term for measuring from the bullet ogive?

I've been reloading for 7-8 years now. I know someone is laughing at me right now but what is the proper term for this measurement?

In my notes for my own personal info so I know what measurement it is I simply have been writing down B.S. O.A.L. for Bullet Shoulder(ogive) OAL.

But I know there must be a proper term for this measurement. What is it?

Thanks. Sorry for the dumb question.
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Old July 30, 2016, 07:24 AM   #2
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No help here but if there is a proper term I'd like to know too.
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Old July 30, 2016, 07:26 AM   #3
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Never a dumb question. When sizing the case, the distance from the shoulder or datum line to base of the case is headspace, its letting you know how much room is left between the head of the case & the bolt face. Over All Length, is the measurement from the head of the case to the tip of the bullet. Not the most accurate measurement but when loading into a magazine or chamber, its standard for the firearm to operate. Ogive measurement let's you know the amount or space to the rifling. Hope I helped.
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Old July 30, 2016, 07:38 AM   #4
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I believe the OP knows what it accomplishes and the proper use and technique. The question is - does't it have a special name?

This is the tool I use. It works for bullet seating as measured from the ogive and it is useful for determining exactly how much the shoulder is being bumped back.

http://www.midwayusa.com/product/746...28-30-calibers
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Old July 30, 2016, 07:50 AM   #5
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Maybe there is no proper term, in which case we can invent one.

I suggest calling it the Duncan measurement after the one who posed the question.
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Old July 30, 2016, 08:38 AM   #6
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If any thought had ever been put into a term to describe the distance from the rifling to the bolt face the information would be available from Sinclair and or Hornady. I make tools that allows me to transfer the measurement to a seating die, I call the tool a transfer; I know that is not very catchy but once I know the distance from the rifling to the bolt face I am not required to start over the next day.

We can talk about the tools that are made for measuring the distance from the beginning of the rifling to the bolt face. Most of the tools are made to be bullet friendly meaning the tools have radiuses instead of sharp edges. My tools imprint on the bullet.

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Old July 30, 2016, 08:52 AM   #7
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I saw in a publication stated as "Cartidge base to ogive" or "C.B.T.O." I've always used that to descibe it.
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Old July 30, 2016, 08:54 AM   #8
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BTO sounds pretty good to me.
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Old July 30, 2016, 09:15 AM   #9
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Good question.
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Old July 30, 2016, 09:45 AM   #10
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Berger calls it CBTO, which I have also seen elsewhere and use it in my reloading notes.

http://www.bergerbullets.com/effects...e-cbto-part-1/

I think CBTO is more descriptive and meaningful than labeling it with someone's name. ymmv
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Old July 30, 2016, 09:48 AM   #11
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Yeah, looks like Duncan is out of luck.
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Old July 30, 2016, 10:26 AM   #12
F. Guffey
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Quote:
BTO sounds pretty good to me.
Quote:
If any thought had ever been put into a term to describe the distance from the rifling to the bolt face the information would be available from Sinclair and or Hornady.
BTO is the measurement made by the Sinclair/Hornady tool because the ogive is on the bullet.

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Old July 30, 2016, 10:31 AM   #13
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BTR; case base to bullet contact with the rifling, then there would be BFtoR as in bolt face to rifling.

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Old July 30, 2016, 11:02 AM   #14
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I list both the case and chamber because that is what SAAMI does. Then there are reloaders that speak where SAAMI is silent. SAAMI does not identify head space for the case but reloaders managed to purchased case head space gages even thought 60 + years ago L.E. Wilson started selling case length gages complete with instructions dated 1954.

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Old July 30, 2016, 11:53 AM   #15
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Well, I ain't laughing! I started reloading in 1969 and I can't answer your question. I've done it a few times, and used the Hornady tools designed for the job, but I don't have a clue of the correct term...
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Old July 30, 2016, 12:02 PM   #16
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Actually base to ogive would be a comparative measurement dependent on the diameter of the measuring tool, i.e. The measuring tool diam. would have to be included in the specs.

Example: C.B.T.O. at .177 diam.
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Old July 30, 2016, 12:10 PM   #17
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Never liked using initials instead on of words. BTO, BTR or BTU's. Sorry, that one is National Security.
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Old July 30, 2016, 12:15 PM   #18
F. Guffey
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Quote:
Actually base to ogive would be a comparative measurement dependent on the diameter of the measuring tool, i.e. The measuring tool diam. would have to be included in the specs.

Example: C.B.T.O. at .177 diam.
Actually? I am the fan of transfers and standards.

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Old July 30, 2016, 12:26 PM   #19
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What SAAMI does not use is the ogive for any measurement. OAL is measured from the pointy bit to the flat bit of the cartridge.
The ogive is on a different part of nearly every bullet type with the same weight. Look at the .224" 55 grain bullets from Sierra.
https://www.sierrabullets.com/produc...lets/rifle.cfm
"...C.B.T.O. at .177 diam..." Is at least a standard. Isn't used by anybody, but it's a standard.
"...SAAMI does not identify head space for the case..." That's because headspace is a rifle manufacturing tolerance only. Cartridges do not have headspace.
"...60 + years ago..." 62. Last March. snicker.
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Old July 30, 2016, 10:31 PM   #20
Duncan74
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Well this turned into a good thread. Someone was explaining all the measurements. I appriciate the time you took to do that but I completely understand all the measurements and how they are taken and I have all the tools to take the measurements.

I use the Hornady bullet comparator that goes on your calipers to take this measurement and the Hornady headspace comparator to check my head space. I use the Hornady OAL gauge to find my max OAL length and use the bullet comparator to take the measurement.

Then when I start working up loads for a gun I will then step back and load 5 shells to test at each length off the lands in .005" increments. .005", .010", .015", .020", and .025" to find out if the gun likes the bullet close to the lands or more bullet jump. Although a lot of bolt action rifles with a lot of throat wear the max OAL won't actually be the real max OAL because the cartridge won't fit in the magazine because the actual OAL is to long. So sometimes my max C.B.T.O. for certain rifles is simply the max length that the magazine will function with.

I was just curious if there was a proper term for this measurement from the back of the case to the bullets Ogive. As I said I personally for my own notes write these measurements down as B.S.O.A.L. For what I call the Bullet Shoulder(ogive) O.A.L.

I was just curious if there was a actual universal term for this measurement so that when discussing bullet seating lengths on this forum with everyone; people would know what I was talking about. I assumed or thought for sure their would be a definite term for this. It sounds like maybe the actual term is C.B.T.O for Cartridge Base To Ogive?!?

Thanks fellas. Good discussion!

Last edited by Duncan74; July 30, 2016 at 10:44 PM.
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Old July 30, 2016, 10:54 PM   #21
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SAAMI gives maximum and minimum measurements for case manufacture. That is all chamber specs do. I consider headspace the matching of the two. Without the standardization of the cartridge case, chamber headspace would be meaningless. The chamber specs actually dictate where the ammunition manufacturers place the ogive of the bullet. Some may fall way short of the rifling, but no loaded SAAMI spec ammo will exceed that point. You will just have a lot of "Freebore".
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Old July 30, 2016, 11:44 PM   #22
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Duncan74
Looks like no one really answered the question. I guess what ever works for you to reference your notes is best. For me when I read just the initials, its like trying to figure whats on car vanity plates. I just wright the whole thing out. If it doesn't rain in the morning, I'll be trying some jump rounds. Be Safe. Chris
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Old July 31, 2016, 05:27 AM   #23
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Quote:
What is the proper term for measuring from the bullet ogive?
From the bullet ogive TO WHERE????

Ogive is the curve of the bullet's forward portion. Hornady defines both a tangent and a secant ogive.

Your question is unclear to me, exactly what you are measuring, from where to where??
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Old July 31, 2016, 09:17 AM   #24
F. Guffey
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Quote:
C.B.T.O for Cartridge Base To Ogive?!?
The bullet has an ogive, somewhere along the ogive the bullet contacts the rifling meaning the chamber does not have an ogive.

Quote:
I use the Hornady bullet comparator that goes on your calipers to take this measurement and the Hornady headspace comparator to check my head space. I use the Hornady OAL gauge to find my max OAL length and use the bullet comparator to take the measurement.
Back to calling everything a head space tool and everything having head space. The Hornady tool is a comparator, if you measure before and again after you have just about mastered the comparator. The case does not have head space. Back to the Wilson case gage, it is a datum based tool, the complicated part about the Wilson case gage with a datum is the way they ZEROED the tool; Hornady has never caught on to that concept, the same goes for reloaders.

You are missing a measurement; I am the fan of transfers, I transfer the measurement from the chamber to the seating die. I know that makes no sense to anyone but I do not need the Hornady tool nor do I need to measure the length of the case from the rifling contact point on the bullet to the bolt face.

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Old July 31, 2016, 09:51 AM   #25
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The case has the chamber's specs as a dimension guide line. You could load a few of the wrong cartridges in a rimmed chamber and still pass the chamber headspace specs. The chamber DOES have a dimension to agree with the ogive on a bullet and bullet diameter. That little angle you grind on forward of the freebore varies with different cartridges. I suspect the angle helps the bullet stay concentric with the barrel because it agrees with the curve of the ogive.
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