In his various articles, Jack O'Connor often mentioned what he felt was ethical hunting range. He recommended zeroing a big game rifle so that the bullet did not exceed a maximum of 4" above the line of sight to take advantage of the rifle's trajectory and minimize or eliminate holding over the target. Although Mr. O'Connor didn't use the term “maximum point blank range” (MPBR), that is what he was essentially referring to. Briefly stated, a “six Inch maximum point blank range” allows you to aim at the center of the heart/lung area of your targeted big game animal and your bullet's trajectory does not exceed three inches high or three inches low during its flight to target. Three inches above or below the point of aim is peanuts and will result in a killing shot on even the smallest big game animals without adjusting for bullet drop.

Chuck Hawks, his article “The Kill Zone of North American Big Game Animals,” has listed estimated heart/lung area diameters. They are as follows:

Pronghorn antelope = 8.5"-9"
Small deer = 8.5"-9"
Medium size deer = 10"-11"
Large deer = 11"-12"
North American wild sheep = 12"-13"
Mountain goat = 13"-14.5"
Caribou = 14.5"-15.5"
Elk = 14.5"-15.5"
Moose = 18"-21.5"

As you'll readily notice, the center of body hold range using a six inch kill zone circle allows for hunting accuracy, meaning shooter error, some animal movement and a small amount of wind drift. This is what makes the six inch MPBR a reasonable, practical and ethical approach on animals ranging in size from pronghorn antelope and small deer on up.

The advantages of zeroing a hunting rifle this way are huge. Forget ballistic reticles, forget holdover, forget knob turning and forget what power your riflescope is set to. Your job is simply to get within the center of body hold range of your animal, wait for the best moment and hit the trigger. Quadruped grass-eaters don't always pose at exact ranges, nor do they always stand perfectly broadside. An angling or slight raking shot does reduce the exposed vital area. Again, the six inch center of body hold allows for a small amount of reduced kill zone due to animal posture, even on a pronghorn.

Here are the ranges at which the bullet drops 3" (the maximum point blank range) when zeroed for a maximum 3" rise for a few typical factory loads. These are calculated for a scope mounted 1.5" above the line of bore. (See the "Rifle Trajectory Table" on the Tables, Charts and Lists page for other calibers and loads.):

• .243 Win/100 grain = 283 yards
• .257 Wby Mag/120 grain = 317 yards
• .270 Win/130 grain = 294 yards
• 7mm Rem Mag/150 grain = 305 yards
• .30-30 Win/150 grain = 225 yards
• .308 Win/150 grain = 267 yards
• .30-06 Spfd/180 grain = 263 yards
• .300 Win Mag/180 grain = 290 yards
• .338 Win Mag/225 grain = 274 yards

When you anticipate hunting in conditions with unpredictable winds, like canyon areas, an easy solution is to zero for a four inch center of the body hold trajectory (4" MPBR). Jack O'Connor often hunted in such places. For substantially larger animals such as elk and moose, you can zero your rifle for a nine inch center of the body hold (9" MPBR) to increase your effective range. It is an easy way to hunt and the fastest way to take a big game animal without unnecessary hesitation or needless computations.