What Is Caliber of Ogive?

Written by Sierra Bullets New Product Development Manager Mark Walker

During one of our recent product releases, we listed the “caliber of ogive” of the bullet in the product description. While some understood what that number meant, it appears that some are not aware of what the number is and why it is important. In a nutshell, the “caliber of ogive” number will tell you how sleek the front end of the bullet is. The higher the number is, the sleeker the bullet. It also makes it easy to compare the ogives of different caliber bullets. If you want to know if a certain 308 caliber bullet is sleeker than a 7mm bullet, simply compare their “caliber of ogive” numbers.

So exactly how do you figure “caliber of ogive”? If you look at the drawing of the 30 caliber 175 gr HPBT bullet #2275 (below), you will see that the actual radius of the ogive is 2.240. If you take that 2.240 ogive radius and divide by the diameter (or caliber) of the bullet you would get 7.27 “calibers of ogive” (2.240 ÷ .308 = 7.27).

base-to-ogive1

Next let’s look at the print (bel0w) of our 6.5mm 142 gr HPBT #1742 bullet for comparison. The actual radius of the ogive is 2.756. Like with the 30 caliber 175 gr HPBT bullet #2275, if you divide 2.756 by the diameter (or caliber) of the bullet you get 10.44 “calibers of ogive”. As most people know, it has been determined through testing that the 6.5mm 142 gr HPBT #1742 has a significantly higher ballistic coefficient than the 30 caliber 175 gr HPBT bullet #2275. However by simply comparing the “caliber of ogive” number of each bullet you can easily see that the 6.5mm 142 gr HPBT #1742 is significantly sleeker than the 30 caliber 175 gr HPBT bullet #2275 even without firing a shot.

base-to-ogive2Some people would say why not just compare the actual ogive radius dimensions instead of using the “caliber of ogive” figure. If we were comparing only bullets of the exact same diameter, then that would be a reasonable thought process. However, that idea falls apart when you start trying to compare the ogives of bullets of different diameters. As you can see with the two bullets presented above, if we compare the actual ogive radius dimensions of both bullets the difference is not much at all. However, once again, testing has shown that the 6.5mm 142 gr HPBT #1742 has a significantly higher BC. The only way that this significant increase shows up, other than when we fire the bullets in testing, is by comparing the “caliber of ogive” measurement from both bullets.

Hopefully this will help explain what we mean when we talk about “caliber of ogive” and why it’s a handy number to use when comparing bullets. This information will help you to make an informed decision the next time you are in the market to buy bullets.

This entry was posted in Reloading, Uncategorized and tagged , , , . Bookmark the permalink.

11 Responses to What Is Caliber of Ogive?

  1. Pingback: Sierra | What Is Caliber of Ogive? |

  2. OK, as I understand it, the Ogive starts at the “taper”, heading to the nose of the bullet correct ?
    Thats the point where you come .10 – .50 from the lands to find the “sweet spot” for accuracy.
    Correct?

    Like

  3. firstriverbend says:

    Great explanation of an often confusing subject! Thanks!! 🙂

    Like

  4. DAVID RUPPEL says:

    Good Info. Thank you for posting it.

    Rupe

    Like

  5. reed says:

    I’m just curious. Does any manufacturer apply a ‘progressive ogive” that is, where the radius lengthens or shortens along the axis of the bullet?

    Like

  6. Pingback: Sierra Introduces New MatchKing Bullet | Sierra Bullets

  7. MS Boltovitch says:

    Is this measurement the same as ‘Calibre Head Radius’ I’ve seen quoted, especially for larger, artillery projectiles? Thanks.

    Like

    • This refers to the radius dimension of the ogive. The length of the ogive radius is divided by the bullet diameter to give you a number that is then referred to as “Caliber of Ogive” A 7 caliber ogive would mean a longer ogive radius than a bullet with a 5 caliber ogive.
      – Duane Siercks, Ballistic Technician

      Like

  8. harrison beasley says:

    What is the correct pronounciation of the word “ogive”. I have heard different guys say it different ways.

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s