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Different types of ojives, how are they relavant?

Wheres-Waldo

Gunny Sergeant
Full Member
Minuteman
Nov 2, 2008
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Ive heard of two types of ojives/ ogaves.....Tangent and Secant.

What is the difference in the two, and are they important to the reloader?

I have heard one type doesnt mind being jumped into the lands, while the other prefers being into the lands...?
 
Re: Different types of ojives, how are they relavant?

It's been about 25 years since I took Trigonometry and calculus, and I was no star in the classroom (!), but, an Ogive is the position on the bullet where it becomes full calibre. A bullet with a secant ogive is sharper or more acutely curved from the tip (meplat) to that portion of the bullet where it is the nominal calibre diameter.

The secant ogive, as the flatter curved of the two, would travel (jump) farther to hit the lands, than the tangent ogive bullet, all other things equal.
 
Re: Different types of ojives, how are they relavant?

Secant ogive bullets become longer for the weight, making them more difficult to staballize than a tangent ogive of the same weight. Secants tend to benefit more from controlling freebore than tangents. Many people find slightly better accuracy with a secant ogive bullet, although certainly not always the case.

The curve of a bullet is a section of a circle, most commonly in a tangent ogive that circle is 6 times the diameter of the bullet. The curve joins the widest part of the bullet without intersecting it, it's tangent to the curve. If you continued to draw the curve, the line that makes up the side of the bullet would touch it at one point.

On secant ogive bullets, the curve inersects the side of the bullet, so you end up with a cusp at the ogive. If you continue to draw the curve out, the line with intersect at two points. I think the curve is more commonly 9-10 time the diameter of the bullet with these.

Sierra match kings are tangent ogive, as are most bullets. Secants are made by berger and lapua, are the first two that come to my head.
 
Re: Different types of ojives, how are they relavant?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">an ogive is an ogive........... </div></div>
Not really!

Mike has it right with "Secant ogive bullets become longer for the weight"
It has to do with bearing surface. More bearing surface equals more pressure. This is a good question and something people should know. I've been messing with both Nosler 160gr Accubonds (Tangent Ogive) and Hornady's 162gr A-max (Secant Ogive). Yes they are both 160grs but you'll get considerably different pressures due to the ogive difference, and hence bearing surface difference.
Another thing is that bullets of equal weight with different ogives will have different BC. Generally, and I mean generally, bullets with a secant ogive have higher BC's.

Here is a nice short article on the topic: http://accurateshooter.wordpress.com/2007/07/10/283/
 
Re: Different types of ojives, how are they relavant?

Thanks for the information, and the link. Ill be reading more on the topic.

Trying to gain insight on how to approach tuning my seating depth within the work up I started on last week-end...

More data will be coming on that post tomarrow if the weather is decent.
 
Re: Different types of ojives, how are they relavant?

Best visual explination...
Thanks to 284Win for the link.
liljabulletsectangx350.gif

 
Re: Different types of ojives, how are they relavant?

Tangent bullets will tolerate jump better, and are more "rounded" from the tip to the ogive. The Secant ogive bullets typically like to be close to the lands and have more of a straight taper into the ogive, like a Berger VLD.