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Tangent Ogive VS Secant Ogive

 
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  #1  
Old 04-25-2010, 01:15 PM
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Join Date: Aug 2008
Location: Arvada, Colorado
Posts: 369
Tangent Ogive VS Secant Ogive

Hello,

Not sure how to explain what it is I'm looking for but will give it my best shot. I would like to reform the tangent Ogive on a 300smk to a Secant ogive.

I believe that the Secant ogive radius is determined by so many calibers multiplied by the diameter of the bullet for a given twist rate. In this case the barrel is a Lilja, 30" 1-10 Twist barrel with a #8 Contour.

I am trying to figure this out, so I can make a form tool or program one of my CNC lathes for this contour. If I can determine the radius needed, I then need the length of the Ogive. For me to program this or make a form tool...I need the length of Ogive, Radius and Bulet diameter.

I know, I know this is just a experiment, I am trying to do for myself. I obviously know very little but want to learn. Thanks for looking.

Ray
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  #2  
Old 04-25-2010, 02:16 PM
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Join Date: Apr 2010
Posts: 43
Re: Tangent Ogive VS Secant Ogive

You might get lucky and Bryan Litz will see this and take an interest. His book has the info you are looking for. I don't have a good enough grasp of the subject to try and explain it myself. I do know he posts on this forum sometimes.
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  #3  
Old 04-25-2010, 05:52 PM
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Join Date: Apr 2010
Location: NW Mt.
Posts: 600
Re: Tangent Ogive VS Secant Ogive

A little past me too but here is an article.

Lilja Precision Rifle Barrels - Articles: Calculating Bullet Weights
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  #4  
Old 04-25-2010, 09:10 PM
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Re: Tangent Ogive VS Secant Ogive

Quote:
Originally Posted by SHRTSHTR View Post
I believe that the Secant ogive radius is determined by so many calibers multiplied by the diameter of the bullet for a given twist rate
The radius of a bullet nose is not 'determined' through rule of thumb. It is what it is, and has nothing to do with twist.
Also, it is very unlikely that you could change the radius(much less radius type) on a jacketed bullet without damaging it completely beyond use.

This is a crazy idea...
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  #5  
Old 04-25-2010, 11:30 PM
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Join Date: Feb 2005
Location: Nevada
Posts: 2,782
Re: Tangent Ogive VS Secant Ogive

Quote:
Originally Posted by SHRTSHTR View Post
Hello,

Not sure how to explain what it is I'm looking for but will give it my best shot. I would like to reform the tangent Ogive on a 300smk to a Secant ogive.

I believe that the Secant ogive radius is determined by so many calibers multiplied by the diameter of the bullet for a given twist rate. In this case the barrel is a Lilja, 30" 1-10 Twist barrel with a #8 Contour.

I am trying to figure this out, so I can make a form tool or program one of my CNC lathes for this contour. If I can determine the radius needed, I then need the length of the Ogive. For me to program this or make a form tool...I need the length of Ogive, Radius and Bulet diameter.

I know, I know this is just a experiment, I am trying to do for myself. I obviously know very little but want to learn. Thanks for looking.

Ray
On the first tab of my FREELY distributed application, it has a print of the 300 gr. SMK showing amongst other things the tangent radius for that bullet.

Your longest practical secant ogive radius would be twice the dimension of the tangent ogive radius for the same nose length.

I think I'm giving you right info. If I'm wrong, it was not my intention. Send an email to Bryan Litz, the easiest way to get his e-mail is by going to Berger Bullets.

http://pages.sbcglobal.net/jomoncada...stic_calcs.zip
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  #6  
Old 04-26-2010, 01:22 AM
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Join Date: Jan 2004
Location: Blackfoot, Idaho
Posts: 8,221
Re: Tangent Ogive VS Secant Ogive

The path to success or frustration includes:

Go to Lilja site and down load bullet design spread sheet. That's about all one needs for what you wish to do dimension wise.

The bullet itself cannot be reshaped via lathe to shift from Tangent to Secant ogive. The jackets are too thin. If it were a solid bullet then things could be changed but I doubt it would be worth the effort.

Another path would be to machine the bullet to take a bronze/brass or copper point. Been down that road. Very difficult.......

The best way to make a bullet of the shape desired is to make them from the ground up.

Finally by the time all of the above is attempted Berger will have their new offerings on the market and trump all of your efforts.........cheaper.

Also a screw machine is the way to make points in quantity. There aren't many in the hands of people would would make a specific point design.
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  #7  
Old 04-26-2010, 09:22 AM
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Posts: 1,253
Re: Tangent Ogive VS Secant Ogive

Ray,

OR, you COULD just go straight to a Berger bullet in either their secant or hybrid profiles to begin with and save yourself a huge amount of frustration and expense. The notion of reforning the tangent ogive into a secant profile is a waste of time and bullets, trust me on this. Even minor reforming, like pointing noses, can result in seriously degraded accuracy. You're talking about shifting core material and a very heavy jacket here, and a pretty major alteration here. Your choice, but I think you're wasting your time (and bullets) here.

Kevin Thomas
Lapua USA
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