Ogive measurement
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Boyd Allen
Active member
Without spending a fortune, I would get as close as possible with a digital camera, crop, enlarge, print and compare with drawn overlays or templates.
Here's how I have it
Bullet die makers decided they needed a term to verbally reference bullet shape. The thinker in the crowd came up with "ogive" and the resultant definition. Everyone was happy for a while...until an industrious individual figured out a some method to dispute the "exactness" of a particular claim concerning the ogive of a bullet. That sent the thinker back to the drawing board and he returned with the additional terms "secant" and "tangent". Currently, a die maker makes a bullet in his finished die, holds it up to the light and declares the ogive. Based on the manner in which the curved part meets the straight part he may or may not add the additional term - but will in all cases if pressed.
This terminology and its use has satisfied the consumer for all this time....until now. We all knew it was sure to happen just didn't know when.
Bullet die makers decided they needed a term to verbally reference bullet shape. The thinker in the crowd came up with "ogive" and the resultant definition. Everyone was happy for a while...until an industrious individual figured out a some method to dispute the "exactness" of a particular claim concerning the ogive of a bullet. That sent the thinker back to the drawing board and he returned with the additional terms "secant" and "tangent". Currently, a die maker makes a bullet in his finished die, holds it up to the light and declares the ogive. Based on the manner in which the curved part meets the straight part he may or may not add the additional term - but will in all cases if pressed.
This terminology and its use has satisfied the consumer for all this time....until now. We all knew it was sure to happen just didn't know when.
C
Cheechako
Guest
Paul
I have measured ogives and shoulder angles using a digital photo print out. As Boyd said, enlarge it several times the original size, draw a center line, and then establish a measurement ratio using a caliper. Then use a drafting compass to try different ogive diameters until you hit the one that comes the closest.
An 8th grade geometry student can do it. Something much harder is trying to figure out Wilbur's post.
Ray
I have measured ogives and shoulder angles using a digital photo print out. As Boyd said, enlarge it several times the original size, draw a center line, and then establish a measurement ratio using a caliper. Then use a drafting compass to try different ogive diameters until you hit the one that comes the closest.
An 8th grade geometry student can do it. Something much harder is trying to figure out Wilbur's post.
Ray
I kinda like Wilbur's post,
Actually, I like all of Wilbur's posts,
Bullet die making is an Art, it is not an exact science. The bullet your die produces is subject to many variables, not just the cavity of the point die. From a consumer standpoint, the finished bullet you recieve from you bullet maker is an individual entity,the exact description of it's ogive will not aid you in discovering it's accuracy potential or seating depth/load preference. It's accuracy potential is subject to your reloading finesse/experience-- Art ? If you are a one powder, one neck tension,one seating depth kind of reloader you may never experience your bullets full potential.
Joel
p.s. Trasch,if you are trying to duplicate a bullet that you have,you can send a couple to Brian Niemi or other die makers and they can get a new die close, but chances are it won't be an exact duplicate. Best bet would be to cut Brian Niemi or David Detsch or George Ulrich loose and request a good shootin' set of bullet dies for your application ( 100-200 br,etc.) These guys know what works ( for them and for you), and they are all very good at their art.
Actually, I like all of Wilbur's posts,
Bullet die making is an Art, it is not an exact science. The bullet your die produces is subject to many variables, not just the cavity of the point die. From a consumer standpoint, the finished bullet you recieve from you bullet maker is an individual entity,the exact description of it's ogive will not aid you in discovering it's accuracy potential or seating depth/load preference. It's accuracy potential is subject to your reloading finesse/experience-- Art ? If you are a one powder, one neck tension,one seating depth kind of reloader you may never experience your bullets full potential.
Joel
p.s. Trasch,if you are trying to duplicate a bullet that you have,you can send a couple to Brian Niemi or other die makers and they can get a new die close, but chances are it won't be an exact duplicate. Best bet would be to cut Brian Niemi or David Detsch or George Ulrich loose and request a good shootin' set of bullet dies for your application ( 100-200 br,etc.) These guys know what works ( for them and for you), and they are all very good at their art.
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OK, ogive. It ain't a guess.
Ogive is expressed in diameters. Not calibers, diameters. A 7 ogive on a 30 IS NOT the same curve as a 7 ogive on a 6mm.
Here's a way to describe the ogive. We'll draw a bullet ogive on the wall.
- take a soup can and nail it to the wall laying "flat." (or you can just draw a soup can if'n you're artistically inclined and don't want nailholes in your wall....just don't get mixed up and draw a soupcon, wouldn't be prudent)
- now measure the diameter of the soupcon (ooops, soup can) let's just say it's 2 inches.
- now reach up a couple feet above the can and hang a plumb bob on the wall so it comes down in line with the end of the can (oops, there's a nail-in-the-wall!) Now you've got a layed down soup can with a vertical string hanging down juuust in line with the end.
Now comes the tricky part.
- measure up the string 6 diameters from the bottom of the can, in this case that will be 12 inches (6 diameters times 2 diameters) above the bottom or 10" above the top of the can.
- now DRIVE ANOTHER NAIL! (get used to it)
- hook a string to the nail, grab a pencil or a scribe (or even a sawzall if you want a permanent record) and draw an arc from the bottom of the can extending out like the bottom half of a bullet. If you want BOTH sides so's it looks like a bullet then repeat the procedure from the bottom side. (Just don't use the sawzall for this mark unless you want a sheetrock "bullet" to carry in your pocket.......)
- you've just described a tangent ogive.
You'se can do these all over the walls if you want to describe different ogives.
NOW, secant ogive. Move the nail..... keep the length of the string the same but move the nail so that it still intersects at the same point, the corner of the can (not con, no)
- you've just described a secant ogive.
useta'could you could search "ogive definition" on the WWW and get some good pix.
no longer, all pix I found were flawed
hth
al
BTW, the way the realio-trulio dudes do the deed is using a cool device called an Optical Comparator which projects a hunnerd times enlarged image on the wall (no nails) for most 'scruciatin' accuracy. Said image is projected onto a grid........Cool tools indeed optical comparators, definitely better than sliced beets.
Ogive is expressed in diameters. Not calibers, diameters. A 7 ogive on a 30 IS NOT the same curve as a 7 ogive on a 6mm.
Here's a way to describe the ogive. We'll draw a bullet ogive on the wall.
- take a soup can and nail it to the wall laying "flat." (or you can just draw a soup can if'n you're artistically inclined and don't want nailholes in your wall....just don't get mixed up and draw a soupcon, wouldn't be prudent)
- now measure the diameter of the soupcon (ooops, soup can) let's just say it's 2 inches.
- now reach up a couple feet above the can and hang a plumb bob on the wall so it comes down in line with the end of the can (oops, there's a nail-in-the-wall!) Now you've got a layed down soup can with a vertical string hanging down juuust in line with the end.
Now comes the tricky part.
- measure up the string 6 diameters from the bottom of the can, in this case that will be 12 inches (6 diameters times 2 diameters) above the bottom or 10" above the top of the can.
- now DRIVE ANOTHER NAIL! (get used to it)
- hook a string to the nail, grab a pencil or a scribe (or even a sawzall if you want a permanent record) and draw an arc from the bottom of the can extending out like the bottom half of a bullet. If you want BOTH sides so's it looks like a bullet then repeat the procedure from the bottom side. (Just don't use the sawzall for this mark unless you want a sheetrock "bullet" to carry in your pocket.......)
- you've just described a tangent ogive.
You'se can do these all over the walls if you want to describe different ogives.
NOW, secant ogive. Move the nail..... keep the length of the string the same but move the nail so that it still intersects at the same point, the corner of the can (not con, no)
- you've just described a secant ogive.
useta'could you could search "ogive definition" on the WWW and get some good pix.
no longer, all pix I found were flawed
hth
al
BTW, the way the realio-trulio dudes do the deed is using a cool device called an Optical Comparator which projects a hunnerd times enlarged image on the wall (no nails) for most 'scruciatin' accuracy. Said image is projected onto a grid........Cool tools indeed optical comparators, definitely better than sliced beets.
R
Roy Allain
Guest
Wilbur, what?
C
Cheechako
Guest
The guy didn't ask for a tutorial on bullet making or on ogives, he simply asked if tools were available to measure an ogive.
Ray
Ray
C
caroby
Guest
"BTW, the way the realio-trulio dudes do the deed is using a cool device called an Optical Comparator which projects a hunnerd times enlarged image on the wall (no nails) for most 'scruciatin' accuracy. Said image is projected onto a grid........Cool tools indeed optical comparators, definitely better than sliced beets. "
Yes....
Mind bending thread fer sur...
I know of no device to measure an ogive >>accurately<< other than the Optical Comparator the die makers use.....
cale
Yes....
Mind bending thread fer sur...
I know of no device to measure an ogive >>accurately<< other than the Optical Comparator the die makers use.....
cale
M.D.Spencer
New member
the Optical Comparator is what I use. An it's a Lufkin. Not that it's important.
Boyd Allen
Active member
Al,
Although a picture is undoubtedly worth a thousand words, evidently the reverse is not always true.
Although a picture is undoubtedly worth a thousand words, evidently the reverse is not always true.
C
Cheechako
Guest
Al - My post was not aimed at you or anyone else in particular. It was just an observation.
I always enjoy your posts no matter what the subject is.
I have been know to stray off the subject from time to time, and even go so far as to hijack a thread.
It would be a dull Forum if we never did that. I belong to a couple of Forums that are very strict and they are not near as much fun as BR Central.Ray
Boyd Allen
Active member
Al,
A couple of other things... According to Hornady, for their secant ogives, the string is twice as long. And according to Dan Lilja, locating the nail gets a bit complicated. Hornady's drawing is a bit sketchy. If you draw a bullet that has a truncated cone for the ogive (straight line from end of shank to edge of meplat), whatever radius that you use for a secant ogive can be used to draw arcs that have pivot points where the profile of the cone intersects those of the shank and the meplat. Where these arcs cross is the the pivot point for laying out the curve of the secant ogive. (pictures would still be a lot better)
A couple of other things... According to Hornady, for their secant ogives, the string is twice as long. And according to Dan Lilja, locating the nail gets a bit complicated. Hornady's drawing is a bit sketchy. If you draw a bullet that has a truncated cone for the ogive (straight line from end of shank to edge of meplat), whatever radius that you use for a secant ogive can be used to draw arcs that have pivot points where the profile of the cone intersects those of the shank and the meplat. Where these arcs cross is the the pivot point for laying out the curve of the secant ogive. (pictures would still be a lot better)
geo.ulrich
Member
o.k. let me try to explain and sort through some of what we have here.the ogive number times the caliber will give you the radius of the ogive,example 7 ogive x.308=2.156 radius.this system works fair as nobody really cares if radius is alittle larger or smaller.this is also the simpler way to check with an optical comparater.heres the catch when checking with a comparater you can get close but not always perfect,you can have a small amount of light to the overlays used.a cmm can be used and would check a whole bunch closer.i use the comparater with 40x lens with overlays.now the ammuntion mfg's thsat i've worked with use a more complicated dimensioning system they work from base and every .050-.100 up give a diameter to hold this is a whole bunch more precise but i really don't believe its needed.now for the tangent ogive part actually there are few true tangent ogive dies being made, thats made from carbide.by the time you edm the cavity with the electrodes being consumed as they burn and final lapping and polishing there is to much hand work to hold all dimension's perfect.also with the different diameters that everybody wants this changes the length of the bearing surface quite alot.(.0001 will change bearing length sometimes .010 in length)i hope this sheds some light on this subject. george
M
mks
Guest
While the optical comparator is a fine tool, and enlarging a picture will work too, one can calculate the ogive with two measurements. Just measure the base to ogive distance at two points of known diameter both smaller than the bullet being measured. (The 0.224 and 0.284 bullet comparator inserts for a 0.308 bullet, say.) You will also need to know the standard base to ogive distance (the length of the cylindrical base part of the bullet.) Plug these measurements into the profile equation (the second equation in the tangent ogive section at http://en.wikipedia.org/wiki/Nose_cone_design) and solve for ogive radius. If it's a secant ogive, you'll need three measurements.
There's also a classic NASA paper with a drawing and equations in the appendix at http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650020584_1965020584.pdf
Cheers,
Keith
geo.ulrich
Member
Kieth, a cmm uses at least three points to check a radius otherwise it could be a angle or a radius.i wonder how equation would figure a double or triple radius ogive that alot are using now. hope you can shed some light on this.as i said before the factories use a print that gives diameters every .050- .100 up from base this includes bearing surface and ogive section. george
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M
mks
Guest
George,
Two measurements only work if you know for sure that its a single tangent ogive, and three if you know its a secant ogive. If it has multiple radii, then you need two or three measurements per radii, and each set of measurements must be from that part of the profile. With an unknown double or triple radius bullet, it could be difficult to figure out where one radius starts and another begins so that you got the necessary number of measurements from each section. I haven't seen a factory print before. That would be interesting if you could post one of the latest designs.
Cheers,
Keith
geo.ulrich
Member
Keith, i would love to do that BUT you know the deal with all being proprietary and know allowing use without consent is a pretty big deal to mfg's. george