August 2 2014 Latest news:
Rifle bullet trajectory
Rifle bullets, no matter how fast they go, do not travel in a straight line – they travel in an arc. The bullet crosses your line of sight on the upward curve and then again on the downward curve of the arc. Where it crosses your line of sight depends on how the sight is set. And remember: higher velocity, lightweight bullets travel in a shallower arc than slower, heavier ones.
The point blank range of a rifle is the maximum distance to which you can shoot, by holding ‘dead-on,’ and still produce a hit within your acceptable zone. You will see that the point blank range depends not only on your rifle, cartridge load and zero range, but also on the target size – the point blank range of a particular set up on a rabbit is much shorter than it is for a big deer.
Setting your rifle for the point blank range makes use of the trajectory arc to its fullest potential. This is where you have to decide on how much deviation from the line of sight you are prepared to accept on a given target. For rabbits this may be as little as one-inch, in as much that a bullet strike one-inch from the point of aim will still result in a humane kill. On a red deer, a deviation of four inches might be deemed acceptable.
To zero your rifle for point blank range you need to know the trajectory of your bullet. So conduct tests at various ranges with different zeroing. The rifleman who zeroes his outfit to be dead-on at 100 yards is limiting both himself and his ability to shoot at any range greater than about 130 yards because his bullet will fall away very quickly after the 100-yard mark.
To make use of the point blank range principle you must imagine shooting at your quarry through a tube, the radius of which is the amount of deviation you are prepared to accept. So, for our rabbit shooter, the tube is two inches in diameter (one inch above the line of sight, one inch below the line of sight). Similarly, for our deer stalker, the tube is eight inches across.
The point blank range is the length of the tube that you can shoot through without the bullet touching the sides. The actual zero range will depend upon the particular rifle, scope and cartridge combination. You will see though, that being able to shoot beyond your zero range will greatly increase your ability to ensure a humane kill.
Extending your zero range greatly affects ability to shoot at targets both close to, and far away from you. In the field, a deviation of two inches on small deer is acceptable– that’s the stalking certificate standard. But by sighting in two inches high at 100 yards you can aim ‘dead-on’ at much greater range without affecting your ability to shoot at shorter ranges than the standard 100-yard zero allows.
That is the principle of the point blank range. It’s a great asset to any rifleman.