Bullet Heads

[Lewdan 17]

Hi, Can anyone explain what is ment when using the terms -- sectional density and the ballistic coefficient in relation to bullet heads. i use a 50grain Sierra varminter Blitz head, and the figures given are .142 for the S/D and .222 for the B/A. How do these figures relate ieif these figures are higher does it mean the bullet is more efficient/ accurate.Be interesting to know!!

Thanks.

LD

[provarmint 25]

http://www.exteriorballistics.com/ebexplained/5th/221.cfm

http://www.jbmballis...s/secdens.shtml

 

Sectional density (SD) is the numerical result of a calculation that compares a bullet's weight to its diameter. To calculate a bullet's sectional density divide the bullet's weight (in pounds) by its diameter (in inches), squared. The higher the SD number the better the SD, and the heavier a bullet is in proportion to its diameter.

 

Ref (The Sectional Density of Rifle Bullets)

By Chuck Hawks

Edited November 2, 2011 by provarmint

[SNAP SHOT 194]

As above for the SD, Where as the Bc. or ballistic coeifficient is how aerodynamic A bullet is as it travels through the air,

 

Simply put a round nose bullet will have a poor bc, and will be a low number like .125 for example, the higher the number the more efficent the bullet will be in flight with regard to flow of air around the bullet head...

 

you might find this an interesting read mate...

 

http://www.hornady.com/ballistics-resource/external

 

 

Atb.

 

 

 

Snap.

[Lewdan 17]

Bloody hell guys!!, will take me quite a while to pick the bones out of all this info But there again i did ask may keep me busy for some time!

Thanks & much appreciated.

L.D.

 

PS, is there a minimum BC number i should be looking for in .223? what is regarded as acceptable for hunting with this calibre?

Cheers.

[khakibob 1]

G'day Lewdan

Here's a simple way to explain sectional density.

If you were to drop two projectiles with the same shape but different lengths off a roof into a vat of butter,the one with the highest SD would penetrate further.

It would be the one longest relative to the surface area.

 

If one was blunt instead of sharp,& all things else being equal the sharpest would go further.The sharpest will have the highest balistic coefficient.

 

Balistic coefficient is not something I would worry about in a hunting bullet,as long as you can tell the front from the back when you look at it will be fine for a few hunderd yards in a smokeless rifle.

Sectional density is less important these days as we have an abundence of well constructed & premium bullets which perform with reliability,not just copper jacketed lead.

 

Its interesting trivia & good to have an understanding off but keeping it simple is a good rule.

If your trying to shoot something at the large end of the 223 capacity, nosler partition 55gr would be one choice,but not as good as a 243 with standard 80gr bullets.

 

Cheers

Khakibob

[jamie g 17]

Bloody hell guys!!, will take me quite a while to pick the bones out of all this info But there again i did ask may keep me busy for some time!

Thanks & much appreciated.

L.D.

 

PS, is there a minimum BC number i should be looking for in .223? what is regarded as acceptable for hunting with this calibre?

Cheers.

 

 

look at the new hornady 53 grain vmax. bc of .290

[dicehorn 38]

Bloody hell guys!!, will take me quite a while to pick the bones out of all this info But there again i did ask may keep me busy for some time!

Thanks & much appreciated.

L.D.

 

PS, is there a minimum BC number i should be looking for in .223? what is regarded as acceptable for hunting with this calibre?

Cheers.

 

 

look at the new hornady 53 grain vmax. bc of .290

 

Hm........ .003 more than the 20 calibre 39gr BK !! - if we can believe any of the manufacturer's claims

[matt_hooks 188]

One thing to remember. Sectional density is accurately defined by measurement. Ballistic coefficient is discovered by experimental measurement, and the bullet companies do this in perfect conditions to obtain the best BC possible for their product.

 

It's far more important that your barrel "likes" the bullet than a few points of BC. A high BC will mean a slightly slower loss of speed, and slightly less wind effect, but is meaningless if the bullet groups like a shotgun with the particular bullet.

 

A point of terminology, there is no such thing as a bullet head. The projectile in a rifle or handgun cartridge is a bullet, the entire round of ammunition is called a cartridge.

[shootlodge 145]

Rocket science bud !

[tegater 789]

One thing to remember. Sectional density is accurately defined by measurement. Ballistic coefficient is discovered by experimental measurement, and the bullet companies do this in perfect conditions to obtain the best BC possible for their product.

 

It's far more important that your barrel "likes" the bullet than a few points of BC. A high BC will mean a slightly slower loss of speed, and slightly less wind effect, but is meaningless if the bullet groups like a shotgun with the particular bullet.

 

A point of terminology, there is no such thing as a bullet head. The projectile in a rifle or handgun cartridge is a bullet, the entire round of ammunition is called a cartridge.

I was always brought up to believe they were called Bullets and cases, and the complete article was called a round.

 

Hence the reason, military ammunition liners tell you for example "100 rounds of 7.62"

 

Maybe though the army have got it wrong

[matt_hooks 188]

Au contraire Teg, that's exactly what I said. Read my post again.

the entire round of ammunition is called a cartridge.