Long Trajectory VS Short Trajectory

[Spess]

I was on the Winchester ammo sight today and I was looking up ballistics charts on some ammo and I saw that the charts had both long trajectory and short trajectory. What is the difference and why would they have different Zeros on the same chart(IE Short Traj- 0=100yrds Long Traj-0=200yrds?

[Coyote Hunter]

Spess -

The difference is the zero point.  The long range zero will have a higher mid-point trajectory.  Personally, I don't use either - I calculate MPBR (Maximum Point Blank Range) using a FREE ballistic calculator caled "Point Blank" that is available from www.huntingnut.com.

Take my 7mm Mag for example.  My handloads shoot a Barnes 160g XLC at 3020fps.  (I use a 160g Grand Slam to hunt with, the Barnes is just for demonstration purposes.)  If I assume I want to hit a target 6" in diameter; I plug the bullets ballisitic coefficient, muzzle velocity, bullet weight and height of the sights/scope above the bore's centerline into the calculator.   The ballistic calculator the tells me to zero at 257 yards for a MPBR of 302 yards.  It also tells me that at 100 yards the bullet should be 2.6" high.

After zeroing for MPBR, I can rest assured that if I do my part the bullet will never be more than 3" above or below the line of sight all the way from the muzzle to 302 yards.  If I was into head shots, that 3" might not be acceptable - instead I might want 1-1/2" from line of sight, or a 3" diameter target.  In this case the calculator instructs me to sight in 1.4" high at 100 yards for a MPBR of 200 yards.

In my case the longer MPBR (6" diameter target) is suited to the game and terrain I hunt.   If I was hunting heavy timber out east or south, wher 50 yards might be a long shot, the closer zero and shorter MPBR might be more appropriate.

[huntsman]

Coyote Hunter is right on. I use the free calculator at biggameinfo.com to figure the trajectories I want to use for my hunting purposes. For example, I think it is more important with my deer hunting rounds that they hit around 2" high at 100 yards, not that they hit zero at a specific 100 or 200 yard mark. I favor a 2" high and low point of impact window within the normal hunting ranges I expect to encounter (0 to about 200 yards). With the ballistic calculator I can adjust the zero point on the calculator until the trajectory figures match my 2" high at 100 yards requirement. Then I will have points of impact at different ranges figured by the calculator as a guideline. All you need to know is the bullet diameter, weight, velocity, and distance above the bullet path of your scope's sight line to work the calculator.

The calculator is an invaluable tool if you want to increase "hold dead on" range and still know how high your bullet will hit at the height of its trajectory. For instance, raising the 100 yard impact point of my favorite 6.5x55 load to 3" high at 100 yards will add another @70 yards of effective "hold dead on" range. Or, going about it from the range aspect, to add 100 yards of range, the bullet impact at 100 yards would increase to about 3.4" high.

[Zachary]

Where I hunt, shots are anywhere from 50 yards to no more than 150 yards.  As such, a 100 yard zero is perfectly fine for me because the deviation, either up or down, either before or after the 100 yard mark is negligible.

Zachary