Ogives explained

A

Andy Cross

New member
The other day I set down at the loading bench to try and figure out the ralationship of ogive numbers and the lengths indicated by a comparator and a set of calipers. I checked 3 different ogive numbers in both .224 and .244 I gave up trying to sort it out. Would someone like to explain the ogive numbers and what they mean numerically.
Andy.
 
Both excellent answers but I really like the Mathscinote description...this is the first thorough, understandable explaination I've read since reading Powley's papers.

We are limited to what is available anyway unless you roll your own, so any number cruntching might be superfluous and might be caliber specific...

Anyone with a supercomputer might help out here...and could provide another advance in the level of attainable accuracy.

Absent that...at least ogives make setting up the seating depth much easier. :D

Luck
 
I've never seen a bullet being made but my understanding is that the lead core doesn't come all the way into the point. If true, it would make mass calculations based on bullet volume also pointless.

Good blog though, I knew about tangent ogives but not secant. Any BR bullets made with secant?
 
Secant Ogives out in the wild

On the second page of the blog, I mention the JLK, 7 mm, 180 Grain Bullet. It is a secant ogive.
 
TomD said:
I've never seen a bullet being made but my understanding is that the lead core doesn't come all the way into the point. If true, it would make mass calculations based on bullet volume also pointless.
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Tom,

Your statement is true for hollow point designs, but not for full metal jacket ones. And yes, there are full metal jacket match bullets available. Are some of these used for BR competition? I don't know.
 
And to add to Asa's post - there are also FMJ bullets where the core does not fill the point. Some leave an air space, some use a filler.

Al, if you count Long Range as part of Benchrest (it is and I do) there are a very few FMJ bullets used in BR, but most shooters who try them eventually come back to the hollow-points.

99% is a really big number. Any evidence to back that up? I'd venture to say that a goodly portion of "Match" rifles are capable of well under 1 MOA. ("Goodly" is not as big as 99%):p

Ray
 
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alinwa said:
In short ogives are measured in units of diameter. This way you can express or describe ANY caliber without hassle.

A 6 ogive means that the curved section of the tip is curved to match a hunk of a circle of 6 times diameter.

SOOOooooo, if you wanted to draw a tangent 6 ogive on a bullet 1 inch in caliber (diameter) you would stand off 6 diameters (6 inches) and swing a circle which intersects with the bullet "shank" such that it's essentially running parallel when it coincides with the shank.

hth

al
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That was actually very understandable!!
Thanks
Ted
 
i know of several bullets listed as "match" that are fmj's.....not even close to br, but some name makers....from the 50's there is a 6.5 fmj match from norma, form the us gov is the 173 fmj match for the 06 and maybe the m14, and hornady currently makes a 3105 dia fmj bt that is sometime listed as match...........
yep match and br are not necessarily the same...

mike in co
Asa Yam said:
Tom,

Your statement is true for hollow point designs, but not for full metal jacket ones. And yes, there are full metal jacket match bullets available. Are some of these used for BR competition? I don't know.
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Comparing "Match" and "Benchrest" is like comparing citrus and oranges. Benchrest is one of the disciplines of Match shooting. Benchrest is broken down into it's own unique classes but they are all considered Match shooting.

I'm 99% certain that I'm right about this.

Ray
 
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Hi all , Is there any of the CNC machined bullets being used to win LRBR matches in the US . I have to this day not heard of anybody even testing such a product here in Australia..JR..Jeff Rogers
 
Jeff - I've not heard of any, but that doesn't mean it hasn't happened. They do, of course, win a goodly share of the 50 BMG Benchrest matches but that is more because so many shooters use them, not that they are necessarily better than jacketed bullets.

Ray
 
Thanks for the explanation

Hi Guys,
Thanks for the explanation about the ogive numbers. As an optical engineer who knows something about geometry I got the drift right away. One other thing I would like to ask is how easy is it to alter an ogive when swaging your own. Is it just a matter of changing a punch or complete retooling.
Andy.
 
a.JR said:
Hi all , Is there any of the CNC machined bullets being used to win LRBR matches in the US . I have to this day not heard of anybody even testing such a product here in Australia..JR..Jeff Rogers
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Jeff, the last year he shot, Bill Sheheane was noticed at Hawks Ridge shooting some CNC solids. I *think* these were some of his customer's rifles, Bill was pretty close-mouthed about it. One was a .375 in some chambering. Anyway, he'd buy a target & shoot them on the last bench during the regular matches.

I notice that Sinclair's now offers the brand Cutting Edge Bullets for sale. They are not presented as benchrest bullets, rather "match grade target/hunting/tactical." http://site.cuttingedgebullets.com/ From their website, they seem to be aimed at competing with the Barnes, Nosler, Hornady, etc. bullets required in California. The claim is higher precision, and the price goes along with that.

We keep hearing of *world records* shot with CNC solids. "Europe," or the "UK." Can't remember if these were fullbore or BR records, I think fullbore. These were the U.S. $4.00+ each variety. Reminds me of the PRL bullets, which Bill did occasionally use in matches.

In spite of being quite mum about things, Bill did let on that whatever he was shooting worked best with a different kind of rifling, something Barney Lawton was working on before he died. If so, that could be one reason there is so little testing.
 
It is easy AND retooling to an extent. You just swap pointing dies if you have another on hand. As Al pointed out (none intended), a carbide pointing die was seven hundred to a grand years ago...

What do they cost these days?
 
Bearing surface is another bullet term

Folks reference the cylindrical portion of a bullet as the "bearing surface". That term implies the section of bullet that "bears" on the barrel. The actual bearing surface would be the length of the bullet that is equal to or greater than the land diameter (rather than the bore diameter). I'm trying to remember but I believe the land to land diameter of a typical 6mm barrel is .236 - could be off a bit but assume it is. In this case, the length of the bullet that is .236 or greater is the actual bearing surface.

It's perfectly fine with me to call it anything you like .... I'm just sayin'
 
OK, I'll call it "shank." As long as we're just sayin', "cylindrical portion" has some problems too -- double radius bullets being all the rage.
 
admin said:
It is easy AND retooling to an extent. You just swap pointing dies if you have another on hand. As Al pointed out (none intended), a carbide pointing die was seven hundred to a grand years ago...

What do they cost these days?
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It's expensive! Bumper to Bumper, probably $7500-$8000 or so I'm figuring. That would include lead, tumblers, jackets, dies, presses, etc.....
 
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