BC in this case does not refer to the calendar but to the ballistic coefficient (BC). All objects that move through the air must deal with drag. Aircraft, rockets/missiles and bullets. The powered object or winged objects model this resistance to the passage of an object by the drag coefficient. Ballisticians define their drag models through the ballistic coefficient. A coefficient is a comparison between two quantities. The BC is the comparison of the actual bullet to a standard design. There are two primary functions the G1 or G7 drag functions. G1 tends to be the civilian standard while the G7 model is favored by the military. Most bullets have their BC’s calculated on the G1 standard, while the G7 attempts to compensate and provide more accurate calculations based on the boat tail design. Basically, the BC indicates ‘slipperiness’ through the air, the higher the BC indicates a lower drag design, allowing the bullet to travel farther in the time allotted before the projectile is overcome by gravity and crashes into the earth.
Hornady Manufacturing Reloading Manuals
Bullets slow down due air resistance and the bow wave. Bullets, that are supersonic, traveling faster than the speed of sound create a shock wave at the point that absorbs kinetic energy slowing the bullet. Over 500 yards the bullet slows, covering less ground per second. The atmosphere further adds friction that is turned to heat, that is by bullets are hot to the touch, atmospheric frictions plus friction generated by passage through the barrel.
All data comes from Hornady Manufacturing reloading manuals and all calculations are performed on their ballistic computer. This is not necessarily an endorsement, just convenience. Hornady builds quality products, but companies like Sierra, Barnes, Speer and Nosler have excellent products as well.
Hornady Interbond 150 Grain Bullet
We’re going to compare two 150-grain bullets. Take the 150-grain bullet, Interbond a hunting round with a BC of 0.415 starting at 2800 fps (feet per second) covers the first hundred yards in about 112 milliseconds (1000th of a second, i.e. 112/1000 seconds), the shorter the transient time the better. The next hundred yards from 100 to 200 yards takes 121 milliseconds, and velocity is down to 2375 fps, that’s 15% % velocity drop. The bullet will have a velocity of 1810 fps, and takes 651 milliseconds to transit 500 yards or 1500 feet.
150 Grain Round Nose Bullet
Now we look at a 150-grain round nose bullet with a BC of 0.186 starting out at 2800 feet per second. At the 100 yards mark the bullet has slowed to 2337 fps, that is a 255-fps difference between the aerodynamic shape of the Interbond, spitzer (German for “pointed”) and the brush bucking short range round nose. This bullet crossed the 100-yard line and took 117 milliseconds. The bullet drops to a sedate 1904 fps at 200 yards and requiring 141 milliseconds. At 200 yards, the round nose bullets are moving at only 94 feet per second faster than the Interbond is at 500 yards. It takes 141 milliseconds from 100 to 200 yards. At 500 yards, the round nose bullet is moving at a paltry 1053 fps, handgun velocity. From the shooter to 500 yards, it takes this bullet 779 milliseconds and drops over 101 inches or that’s more than 8 feet, from the 100 yard zero. The Interbond bullet zeroed to at 100 yards drops 57 inches in the 400 yards between 100 to 500 yards.
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