Jack O’Connor’s Formula For Shooting Game At Long Range

The top-to-brisket spread of a mule deer buck appears to be about 18-inches, a useful dimension for estimating range and a big target for employing a MPBR for just an 8-inch target. There is plenty of room for a big of error such as a poor shot or a rifle that does not park every bullet inside MOA.

The top-to-brisket spread of a mule deer buck appears to be about 18-inches, a useful dimension for estimating range and a big target for employing a MPBR for just an 8-inch target. There is plenty of room for a big of error such as a poor shot or a rifle that does not park every bullet inside MOA. (Ron Spomer/)

Outdoor Life’s Shooting Editor from 1947 to 1978 routinely shot whitetails, mule deer, even sheep without the aid of range-finding devices. To O’Connor “far” was 500 yards. His philosophy was to resist shots beyond 300 yards. But he also wrote “The hunter… should avoid the 400- and 500-yard shots if he possibly can, but … he should be prepared for them.”

By today’s laser-guided standards, O’Connor’s ideas seem quaint, but before we dismiss them as products of primitive technology, let’s consider what he and his shooting system could do.

Jack’s Way

Upon spotting a suitable animal, old Jack could, inside of a few seconds, assume the steadiest shooting position at hand, aim, fire, and hit his target. Out to 400 yards, rarely 500.

No fumbling for a laser. No smartphone apps. No button pushing. No turret dialing. Just aim, shoot, and break out the skinning knife.

With MPRB system, you don’t need to touch your turret until after your MPBR distance. This makes targeting most game at most ranges commonly encountered dead easy. Just aim for the middle. If time permits, you can always laser range and dial if necessary. By starting with a MPBR zero, you add more reach to any dialing turret system, too.

With MPRB system, you don’t need to touch your turret until after your MPBR distance. This makes targeting most game at most ranges commonly encountered dead easy. Just aim for the middle. If time permits, you can always laser range and dial if necessary. By starting with a MPBR zero, you add more reach to any dialing turret system, too. (Ron Spomer/)

O’Connor was able to do this because he zeroed his rifles to maximize their effective range. “I sight in to put the bullet three inches high at 100 yards,” he wrote. Three inches high? That strikes most 21st century shooters as excessive. The current fashion is to zero at 100 yards, then dial or select from a Christmas tree of reticle lines for 200, 300, 400, etc. Meantime, your buck steps into cover or runs away.

With Jack’s zeroing system, his bullets — usually a 130-grain spire point from a 270 Winchester at about 3,000 fps — would peak no more than 4 inches above point-of-aim (POA) at about 180 yards, strike POA at about 270 yards, fall 2 or 3 inches below POA at 300 yards, and drop about 14 inches below POA at 400 yards. Depending on bullet B.C., drop at 500 yards might be 32 to 36 inches.

This makes aiming easy. If you estimate distance to target somewhere between 100 and 300 yards, hold dead center and score. That’s it. That’s all the more complicated it is. If you don’t find this liberating, you haven’t spent enough time looking at a buck or bull across a big western canyon with a dead laser rangefinder in your hands.

No batteries, no phone apps, no laser rangefinders are needed with the MPBR system for shots out to 300, sometimes 375 yards depending on your rifle, cartridge, bullet.

No batteries, no phone apps, no laser rangefinders are needed with the MPBR system for shots out to 300, sometimes 375 yards depending on your rifle, cartridge, bullet. (Ron Spomer/)

MPBR Afield

To drive home this point, allow me a quick story. Scott and I were climbing for sheep in the Chugach Range. When we’d climbed high enough to crest a little rise and spot two rams, our outfitter was pinned down 100 yards to our left where he’d gone to peek around another ridge. He had the rangefinder. The sheep were steadily walking away.

“What do you put them at?” I hissed. “Three fifty?”

“If not 400!” Scott answered.

“Right on the backline then,” I said. The rams stopped. We fired. Both our bullets landed center chest. Rangefinder readings later showed shooters-to-rams distance at 385 yards, more or less.

Zeroing 3-inches high and then shooting at an 8-inch target (the black) at various distances graphically shows you where you bullets will land. Seeing them within the 8-inch circle and knowing that this diameter easily encompasses the vital zone of most big game animals gives you great confidence in using a center-chest hold at all ranges estimated within your MPBR. On this target the three closely grouped shots on the white circle 3-inches above the center of the red bullseye represent the 100-yard zero. The two above it represent 150-yard and 180-yard shots. The high hole just out of the black illustrates what can happen with less than perfect field shooting and/or a rifle that can throw a shot slightly out of its normal group dispersion. A bit high, but on virtually all N.A. big game, still a killing shot. The three shots around the red bull are from 260 yards. The three lowest shots represent bullet drop at near MPBR, in this case 320 yards. The 3.5” left-right spread shows this rifle grouped slightly better than MOA at this distance (MOA at 300 yards is 3-inches.)

Zeroing 3-inches high and then shooting at an 8-inch target (the black) at various distances graphically shows you where you bullets will land. Seeing them within the 8-inch circle and knowing that this diameter easily encompasses the vital zone of most big game animals gives you great confidence in using a center-chest hold at all ranges estimated within your MPBR. On this target the three closely grouped shots on the white circle 3-inches above the center of the red bullseye represent the 100-yard zero. The two above it represent 150-yard and 180-yard shots. The high hole just out of the black illustrates what can happen with less than perfect field shooting and/or a rifle that can throw a shot slightly out of its normal group dispersion. A bit high, but on virtually all N.A. big game, still a killing shot. The three shots around the red bull are from 260 yards. The three lowest shots represent bullet drop at near MPBR, in this case 320 yards. The 3.5” left-right spread shows this rifle grouped slightly better than MOA at this distance (MOA at 300 yards is 3-inches.) (Ron Spomer/)

That’s the beauty of this system. It’s not gnat’s eyelash precise, but it’s “punch your tag” precise for most big game hunting. I have six rams and dozens of bucks and bulls to prove it.

We call this zeroing system Maximum Point Blank Range (MPBR.) Once you set up for it and practice sufficiently to understand and trust it, you’re ready to shoot quickly and confidently. If you estimate your quarry is no more than 300 yards away, hold center chest and shoot. If you think it’s farther, stalk closer! If that’s impossible and time is running out and you have a steady rest and the wind isn’t blowing and you’re confident you can make the shot and you’re confident the range is somewhere between 300 and 400 yards, hold top of withers and your bullet should drop somewhere into what Jack and his peers called “the boiler room.”

Scott Grange took this fine Dall’s ram while hunting with outfitter Lance Kronberger. By zeroing his 270 WSM for MPBR, all Grange has to do to make the shot at the unknown but estimated range of 350- to 400 yards was hold on the rams backline.

Scott Grange took this fine Dall’s ram while hunting with outfitter Lance Kronberger. By zeroing his 270 WSM for MPBR, all Grange has to do to make the shot at the unknown but estimated range of 350- to 400 yards was hold on the rams backline. (Ron Spomer/)

Those were common shooting ranges in O’Connor’s era. And they still are. Despite what we hear about extreme range hunting, most of us encounter our bucks, bulls, and bears at 300 yards or less, even in the mountain west. Wouldn’t it be convenient to know that to make those shots we only needed to aim center chest and not flinch? That’s just what the O’Connor’s system does. It frees you from dependency on gadgets and batteries, reduces stress and panic at a time when buck fever runs hot, and speeds up your shooting. Instead of fumbling for extra tools, you are free to concentrate on sight picture and trigger squeeze.

Read Next: Long Range Shooting: MOA vs. Mils

All cartridges work with the MPBR zeroing system. The higher the muzzle velocity and bullet B.C., the longer the MPBR will be. The larger your target animal’s vital zone, the longer the MPBR you can select. A bullet that would fall out of the roughly 10-inch diameter heart/lungs of a pronghorn at 300 yards might not fall out of the 24-inch vital zone of a moose until almost 500 yards!

MPBR zero for these two hunters resulted in twin rams taken from roughly 400 yards. Spomer on left was shooting a 95-grain bullet from a Browning X-Bolt in 243 WSSM. Scott Grange on right was shooting a 270 WSM with 140-grain bullet. Their guide, with the rangefinder, was too far away to assist them with a precise range call. MPBR saved the day.

MPBR zero for these two hunters resulted in twin rams taken from roughly 400 yards. Spomer on left was shooting a 95-grain bullet from a Browning X-Bolt in 243 WSSM. Scott Grange on right was shooting a 270 WSM with 140-grain bullet. Their guide, with the rangefinder, was too far away to assist them with a precise range call. MPBR saved the day. (Ron Spomer/)

A 150-grain round-nose from a 30-30 Winchester can stay within the kill zone of a whitetail out to about 220 yards if you zero it 3 inches high at 100 yards. Step up to a 150-grain spire point in a 308 Winchester at 2,850 fps, zero it 3 inches high at 100, and it’s only about 3.5 inches low at 300. Keep sliding up the power scale to a 300 Win. Mag., push a 180-grain Accubond 3,100 fps, zero it 3 inches high at 100 and it won’t drop 4 inches below POA until 340 yards or so. That’s a long poke under most hunting conditions.

Now, if you really want to extend your dead-on MPBR, saddle up a 26 Nosler. Push a sleek, 142-grain Accubond Long Range 3,450 fps and zero it 3 inches high at 100 yards. With this High Plains Sizzler, you can hold mid-chest and drop your bullet into your quarry’s heart at about 370 yards.

This high velocity, high B.C. (aerodynamically efficient) combination is what maximizes reach without the need to dial. But that doesn’t mean you can’t dial. Or use multiple stadia lines. The extra cool thing about MPBR zeroing is that you can add it to your other long range tools. With a ballistic-style multi-stadia reticle, for instance, the center reticle will suffice at all distances out to 300, perhaps as far as 370 yards. The first sub-reticle might then be spot on for 400 yards, the next 450 or 475. It all depends on your bullet’s trajectory curve. But regardless, by setting up your MPBR zero, you’ll extend useable aiming points well beyond what you could with a 100- or even 200-yard zero.

Pronghorns are notorious for needing long-range precision shooting, yet the author has taken dozens cleanly by utilizing MPBR with a variety of rifle and cartridges from 22-250 Rem. through 300 WSM.

Pronghorns are notorious for needing long-range precision shooting, yet the author has taken dozens cleanly by utilizing MPBR with a variety of rifle and cartridges from 22-250 Rem. through 300 WSM. (Ron Spomer/)

Much the same happens with dialing turrets. Where a 100-yard zero might have you “dialed out” at 700 or 800 yards, a 250- to 300-yard zero will let you dial well beyond.

Before we outline the step-by-step process of setting up your MPBR with your rifle and ammo, let’s consider a couple of fine points.

As you study the included ballistic charts and the MPBR system, you’ll begin to realize that our sample trajectory charts don’t fully take advantage of potential. For one thing, by keeping mid-range trajectory no higher than 4 inches above POA, we’re assuming an 8” diameter target. The average deer’s vital zone is closer to 10 inches, perhaps even 12 inches. This suggests we could zero for a mid-range trajectory peak of as much as 6 inches. So why don’t we? Rifle and shooter inconsistency.

Zeroing 3-inches high at 100 yards worked beautifully for Jack O’Connor and his M70 270 Winchester and it did the same for Joe Arterburn and his 270 Win. M70. The 270 Win. was, is, and always will be a great pronghorn round.

Zeroing 3-inches high at 100 yards worked beautifully for Jack O’Connor and his M70 270 Winchester and it did the same for Joe Arterburn and his 270 Win. M70. The 270 Win. was, is, and always will be a great pronghorn round. (Ron Spomer/)

A rifle that groups MOA should keep all shots inside a 3-inch circle at 300 yards. That means any shot could strike 1.5 inches higher or lower than your POA. If your maximum trajectory peak at, say, 150-yards is already 4 inches above POA and you add another 1.5 inches, your shooting 5.5 inches above center chest. Add another inch or two for shake, poor trigger pull and all the other limiting factors in a real world hunting situation and shooting another 2 inches higher or lower is a distinct possibility.

Read Next: Shooting Lessons Learned from Long Range University

This is why being conservative with your MPBR target size is wise. Sticking to an 8- or 10-inch target zone leaves room for error, yours or your rifles. And it contributes to consistency. It’s tempting to take advantage of the much larger vital zone of an elk, for instance, and zero for a max ordinate or 6 or even 10 inches. But what happens when you take a shot at a coyote? Or forget to re-zero for your pronghorn hunt? Setting different MPBR zeros for different game is certainly possible, but most of us will perform better and more consistently with a standard for all our hunting. Part of the “beware the hunter with one rifle” idea. Consistency is nothing to sneer at. So let’s set up your MPBR now.

The combination of an extremely high B.C. bullet (.625) and high launch velocity (3,200 fps) gives the 26 Nosler a delightfully long MPBR of nearly 375 yards on an 8-inch target zone. Peak trajectory comes at about 175 yards.

The combination of an extremely high B.C. bullet (.625) and high launch velocity (3,200 fps) gives the 26 Nosler a delightfully long MPBR of nearly 375 yards on an 8-inch target zone. Peak trajectory comes at about 175 yards. (Ron Spomer/)

5 Step MPBR Plan

1. Select your target size—This is the sure-fire vital zone of the chest of your target species. As discussed above, it can vary wildly from moose to pronghorn or coyote. A safe size form all North American big game species is 8-inches. Scribe an 8-inch circle centered on the chest of a small whitetail and you’ll cover the heart/lungs. An 8-inch target zone leaves you with a maximum trajectory of 4 inches above POA.

2. Select your bullet B.C. and muzzle velocity—Caliber and cartridge don’t matter. Only B.C. and MV affect drop and drift. The higher both numbers, the longer your MPBR will be.

With high B.C. bullets, most modern, bottlenecked cartridges kick up enough muzzle velocity to push MPBR to 300 yards or more with O’Connor’s 3-inch high zero at 100 yards.

With high B.C. bullets, most modern, bottlenecked cartridges kick up enough muzzle velocity to push MPBR to 300 yards or more with O’Connor’s 3-inch high zero at 100 yards. (Ron Spomer/)

3. Optional—Open an on-line ballistic trajectory calculator. There are many. Enter pertinent data and choose a zero range of 250 yards. Create the trajectory chart and note the mid-range trajectory peak, usually 150- to 180 yards. Note also the 100-yard bullet impact. It should be 2 to 3 inches high. Next, increase or decrease zero range as necessary to achieve a mid-range trajectory of 4-inches high. The distance downrange at which bullet drop reaches 4 inches is your MPBR.

4. Testfire—Whether you did or did not run trajectory tables, go to a range and zero about 3 inches high at 100 yards. Check target impact at 150, 180, 200, 250, 300, and 350 yards to determine impact points. The distance at which your bullets consistently land 4 inches or more below POA is your MPBR.

A typical 130-grain 270 Winchester load should produce a trajectory similar to the one numbered in this ballistic table. Note the launch velocity is 3,000 fps, the bullet B.C. .430, right in the ball park for most boat tail spire points. Zeroed 2.93” high at 100 isn’t precisely the 3-inches recommended, but more than close enough. Notice in the 2nd column (Elevation in inches) the bullet peaks roughly 3.5 inches high at 150 yards. It doesn’t drop 4 inches below point-of-aim until roughly 320 yards. This means a steady hold for the middle of an 8-inch diameter target (like a pronghorn’s chest) at any distance from 25 yards out to 320 yards should result in the bullet impacting the vital zone.

A typical 130-grain 270 Winchester load should produce a trajectory similar to the one numbered in this ballistic table. Note the launch velocity is 3,000 fps, the bullet B.C. .430, right in the ball park for most boat tail spire points. Zeroed 2.93” high at 100 isn’t precisely the 3-inches recommended, but more than close enough. Notice in the 2nd column (Elevation in inches) the bullet peaks roughly 3.5 inches high at 150 yards. It doesn’t drop 4 inches below point-of-aim until roughly 320 yards. This means a steady hold for the middle of an 8-inch diameter target (like a pronghorn’s chest) at any distance from 25 yards out to 320 yards should result in the bullet impacting the vital zone. (Ron Spomer/)

5. Verify—Confirm this performance with repeated shooting at paper targets at distances from 50 yards to 350 or so until you’re firmly convinced that you and your rifle can keep all shots inside the 8-inch circle to your MPBR. Obviously a steady rest gives you your best chance, so use one. This test is just to confirm your loads MPBR. You can work on precise field shooting performance later.

Whatever you choose for your target diameter and mid-range trajectory, do not neglect this extensive field testing. Once you see those holes in paper you’ll gain confidence. And then you’ll be ready to find your game, stalk as close as you can, and shoot with confidence, range finder or no range finder.

Something else Mr. O’Connor wrote: “Promiscuous long range shooting should always be avoided.”

Many hunters assume the 300 Win. Mag. shoots far and flat, and it does, but compare its bullet impacts with the 270 Winchester trajectory table and you realize they are remarkably similar out to 300 yards.

Many hunters assume the 300 Win. Mag. shoots far and flat, and it does, but compare its bullet impacts with the 270 Winchester trajectory table and you realize they are remarkably similar out to 300 yards. (Ron Spomer/)
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