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Originally Posted By: savage_manIts about at clear as mud... I guess its one of those things I'll understand with time and experiance.  


You will not get with time... time has nothing to do with it.


BC is the ability of a bullet to slip through the air - the more streamlined a bullet is, the higher BC it has and the less drag it has.


There were some formulas made to calculate BC many years ago, and the formulas were based on flat based bullets.  The formulas worked pretty well.


When the long boat tailed bullet was developed, it worked "OK" with the flat based bullet formulas at high velocities, but as the bullets slowed down, the airflow over the boat tail started taking more effect, and the bullet became even more streamlined.


At this point, the formulas did not work very well.  So they developed new formulas and the G-7 was born.


With SD - you can have have a heavy, blunt nosed bullet and compare it with a streamlined bullet that weighs less.


If you have a 30 calibre 220 gr round nose bullet, and compare it to a 155 gr boat tail spitzer, you get...



220 round nose

Sectional Density: 0.331

Ballistics Coefficient: 0.310


155gr Match King

Sectional Density: 0.233

Ballistic Coefficient: 0.504


You can see that the 155gr has a lower SD and a higher BC than the 220 round nose...


So the two are not related.


If you don't get it now, don't worry - it's all just academic crap anyway, and it's not necessary to understand this stuff to shoot a rifle and have fun.



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