determining/calculating ballistic coefficient

[Timmis2]

I am hoping to figure out the BC for a particular projectile. It's the 56gr. .355" Inceptor ARC for 380 auto. It's their fluted round nose copper/polymer pill. From the manufacturer, I'm not sure what the data they provide means exactly. In some load data they show "BC / SD - .037 / .067 ". I assume they are saying the ballistic coefficient is .037 with a standard deviation of .067. I don't know what SD means in this case. I haven't learned yet how to figure out BC when the manufacturer doesn't publish the BC forthwith or Google doesn't help tremendously. I am going to play with this projectile and reload it for both 380 and 9mm but I would like to punch the BC into ballistic calculators for some data prior to chronographing it myself. Can someone take me to school?

 

[MikeRu]

SD might be sectional density

 

[Timmis2]

SD might be sectional density

ohhh...okay. So the BC is probably an anemic .037

 

[chop house]

ohhh...okay. So the BC is probably an anemic .037

Yup SD is sectional density as stated above and the ballistic coefficient is slightly better than a rock.

 

[Timmis2]

What's the best way to search for the BC of a projectile? Is there a database published somewhere with a large percentage of common and uncommon projectiles?

 

[Longrange57]

What's the best way to search for the BC of a projectile? Is there a database published somewhere with a large percentage of common and uncommon projectiles?

You might search air gun slugs and pellets. A couple of different folks offer BC on slugs of about the size you are looking for.

 

[chop house]

If you know the sd and the form factor you can estimate the bc. Sd is a function of frontal area and mass. The form factor I don't have a handle on yet.

Form Factors: A Useful Analysis Tool

In 2009, Berger Bullets introduced G7 BC’s for boat tail bullets. For those who are unfamiliar with G7 BCs, it’s simply a Ballistic Coefficient referenced to the G7 standard projectile instead of the G1 standard projectile. The G7 standard is a better match for modern long range bullets, so the...

bergerbullets.com

Bullet Database - LoadDevelopment.com

As is often the case, especially lately, when a shooter wants to change to a different bullet or has to buy a different bullet to shoot as their usual choice is not available, they have to check the manufacturers website or on the box to see how the Ballistic Coefficient compares to their...

www.loaddevelopment.com

 

[charlie b]

What's the best way to search for the BC of a projectile? Is there a database published somewhere with a large percentage of common and uncommon projectiles?

I go to the GRT database for projectiles. They have data on a lot of different bullets, but, not all. Other than that you have to trust the mfg until you can fire some (especially for obscure ones and even more so for small pistol cartridges).

There was a website that you could enter a bullet shape/weight and it would calculate a BC, but, I can't remember where it was. FWIW, it wasn't very close for the cast bullets I was shooting back then.

If you have a Labradar you can use the track data to calculate the BC using the calculator on the JBM website. If you are accurate enough you can use the bullet drop over distance to calculate it.

 

[Webster]

I am hoping to figure out the BC for a particular projectile. It's the 56gr. .355" Inceptor ARC for 380 auto. It's their fluted round nose copper/polymer pill. From the manufacturer, I'm not sure what the data they provide means exactly. In some load data they show "BC / SD - .037 / .067 ". I assume they are saying the ballistic coefficient is .037 with a standard deviation of .067. I don't know what SD means in this case. I haven't learned yet how to figure out BC when the manufacturer doesn't publish the BC forthwith or Google doesn't help tremendously. I am going to play with this projectile and reload it for both 380 and 9mm but I would like to punch the BC into ballistic calculators for some data prior to chronographing it myself. Can someone take me to school?

Can you just shoot it at different distances and create a drop chart? You don't need to know the BC.

 

[piie]

I believe the OG Labradar unit provides you with multiple distance velocity measurements on the same shot. which can then be used to calculate the BC. Not sure of the new Labradar units still do this, or maybe one of the other radar units?