Learn veteran hunter and long-range shooter Gary Cook’s fool-proof system for popping predators at 600-plus yards!
A camo-clad hunter blends into the briar-choked edge of a harvested West Tennessee cotton field on a cold January morning, the sun not quite high enough to warm his back. He places a varmint call to his lips and begins the dying rabbit blues.
Within two minutes he spies movement on the far side of the field. Suddenly the coyote halts his progress, parks his butt, and begins to bark. Knowing that the old dog is spooked about something, the waiting hunter raises his range finder and dials in 580 yards to the stubborn coyote. Adjusting for the range, he plants the crosshairs of his AR-15 on the varmint’s chest and squeezes off a shot. The coyote wilts at the impact of the 55-grain Sierra, and kicks his last as the caller grins at his success.
Although it’s been 20 years since Gary Cook made his longest kill with an AR-15 as related above, he’s learned volumes of practical knowledge about guns, bullets and how to kill game at extended ranges. This writer recalls several stories of whitetails that have fallen to Cook’s long-range skills at the 640-yard mark. “It’s the farthest I can shoot on the big bean field on our club,” Cook said.
Cook’s continual curiosity with long-range shooting has led him to some rather unconventional conclusions. The evolution in his thinking has led him to believe that a bullet’s spin rate also has a profound influence on a bullet’s killing ability, rather than just the foot-pounds of energy it expends on game at a given range. And, he’s a big fan of blending some new technology with older techniques to create a near fool-proof long-range shooting system that’s affordable for most hunters and shooters. Applying some of his experience with the 5.56/.223 Remington and other cartridges will enable readers to build their own custom bolt-action rigs for about $1,000, or a long-range AR platform rifle for a couple hundred dollars more.
One Shot One Kill
Taking game at extended ranges is a passion for Cook. He refined long-range hunting skills with a customized Savage bolt-action. He took the action, mated it to a Walther Lothar barrel chambered in .260 Remington with a 1:8 twist rate. Then, he had a bedding block milled that looks similar to an Accuracy International, and that accepts the AI stock skins. “I built the first .260 Remington bolt gun around the .264 Berger 140-grain VLD bullet,” Cook said. The 30-year veteran wildlife biologist’s range work and field experience has led him to opt for longer, high ballistic coefficient bullets driven at fast twist rates to provide killing power on varmints and whitetails at extended ranges. “If this was working so well in a .260 Remington, then I guessed that it would work in a .223 Remington, too,” he added. To get his long-range .223 bolt guns to stabilize the 90-grain Berger VLD bullets, Cook had Brux Barrels build a 1 1/4-inch bull barrel with a 1:6.5-inch twist rate to outfit another Savage action. What is twist rate? Twist rate refers to the rate of spin in the rifle barrel, and is represented in inches per turn. It’s important that your barrel has sufficient twist rate to stabilize the bullets you’re shooting. A barrel that is a 1:10” twist means that the rifling will spin the bullet one revolution in 10 inches. A barrel with a faster 1:6.5” twist means that the rifling will spin the bullet one revolution in 6.5 inches.
“The key to long-range killing is the wound channel that your bullet produces,” Cook said. “You can consistently kill deer with .223s. You are going to hear some gnashing of teeth, but they haven’t been there and done it. I’m getting golf-ball sized exit wounds at 600 yards with a .223 only going 2,800 feet-per-second. I think the fast twist rate is increasing its ability to kill at the extended ranges.”
Each deer season Cook regularly kills deer at ranges between 450 and 640 yards with his .260 Remington. “I couldn’t recover a bullet because they were all passing through. I had a 3 ½-year-old buck at 450 yards that was walking toward me and gave me a chance to shoot him lengthwise through the body. I recovered that bullet under the skin on the back side of his ham. It was a typical mushroom and it traveled in a straight line from his chest to his rear end.”
Cook believes that the Berger VLD bullets are expanding into a typical mushroom on deer-sized game. “I do heavy necropsies on every deer I kill,” the veteran wildlife researcher said. “If the bullet were upsetting and tumbling it would have the tendency to veer from a straight path and create some non-uniform wound channels. The wound channel is straight between the entrance hole and the exit hole.” Cook also maintains that the animals’ reaction to the shot with a fast-twist VLD bullet is indiscernible from one hit in the same location with larger-caliber deer rounds at shorter average ranges.
He has noticed that the Berger VLDs don’t perform the same at shorter ranges, though. “The VLDs aren’t doing as much with short shots under 200 yards,” Cook said. “I’m getting exits, but they aren’t blowing out as big an exit channel as at the longer ranges. Berger calls it a ‘delayed expansion.’ They claim their bullets go in 2-3 inches before they start expanding.” Cook will continue his quest to determine what is happening to the .223 bullets when they impact game. “I haven’t recovered any .223 bullets on deer shot out to 600 yards yet.”
Cook is also a fan of Hornady’s high-B.C. AMax .224 bullets. “The AMax bullets do the same as the Bergers insofar as wound channels,” he said, “but the Hornadys don’t match the mil dot scopes we’re using. The B.C. is lower on the Amax. But, the AMax perfectly matches the Shepherd P2 or V2 scopes, so we’re shooting the AMax with the Shepherds and the Bergers with mil dots.”
Surprisingly, Cook was finding a couple of things that were not typical in his range testing. “Some of the ballistic coefficients reported on some of the bullets are higher than the published data in the exterior programs,” Cook said. “Sometimes, I had to adjust the B.C. up in my computer programs above the published data for a particular bullet, and then load down to drop the velocity to get them to match the distance between the mil dots.” His long-range groups were producing smaller M.O.A groups at the longer ranges, too. “The Berger VLDs don’t ‘go to sleep’ until 300 yards,” Cook said. “Once they pass that range they become even more stable and consistent in flight.”
After quite a bit of study of exterior ballistic programs, such as RCBS.LOAD produced by RCBS, Cook learned that if he matched a bullet with a ballistic coefficient of around .500, or greater, and kept the velocity between 2,700 and 2,850 fps, then it corresponds well with the spacing of the aiming dots in a mil dot scope in 100-yard increments between 300 and 700 yards. “I started loading down to match an optical system that anybody can use,” Cook said. “Here’s how you can do that: the Berger VLDs drop at a consistent rate out to 700 yards. By comparison, a bullet with a lower ballistic coefficient, say in the .300s or .400s, most loads match a readily available optics system and have to be ‘dialed in’ in other target scopes, so why not shoot a load that matches a readily available optic system?”
Some manufacturers are savvy to couple high ballistic coefficient bullets and fast twist rates with their recent AR product lineups. Bushmaster now offers, through their custom shop, the Precision Marksman Rifle (PRM) with an 18-inch barrel with a 1-in-7-inch twist. Some custom barrel makers, such as Brux Barrels are building even faster-twist AR barrels for some customers. “We have built several AR barrels with a 1-in-6.6-inch twist for an armorer with one of the Army Reserve rifle teams,” Norman Brux said. “He’s building them to shoot the 90-grain Sierra bullets in competition. I suspect they are loading single-shot for the 600 yard slow-fire portion of their matches.”
Connecting the Dots
The concept of using mil dots to range a target is, in its simplest form, the geometry of a triangle. If you know the value of two legs of the triangle and the angles of the legs you can compute the third “unknown” leg’s value. With the mil dot reticle your two knowns can give you the third “unknown,” which is the distance to the target. With Cook’s method of using a laser range finder, the distance becomes a known value allowing the computation of the unknown holdover.
He simplifies the concept even further by using a range-finding mil dot scope, but doesn’t use it to estimate range. Mil dot scopes were invented by the military as a range finding devices. Instead of using the mil dot as a range-finder, Cook uses a laser range finder to do his calculations. What he’s found is that matching a bullet with a .500 B.C. with the right velocity he’s able to match closely the mil dots to ranges between 300 and 700 yards.
When zeroed at 100 yards, the distance between first mil dot and the cross hairs is 10.8 inches at 300 yards. The second dot corresponds to 28.8 inches of rise at 400 yards; the third dot is 54 inches above zero at 500 yards, and the fourth dot gives 86.4 inches rise at 600 yards. The top of the post equates to 126 inches of hold-over at 700 yards.
“What everybody is promoting today is that you have to have a gun that shoots 4,000 feet per second and two thousand dollar scope to kill game at long range,” Cook said. “Everybody is dialing in their trajectory. That’s great if you are sitting on a bench and punching paper. If you’re in my business, then you need to be ready to kill something right now. You need to be able to hold a fixed aiming point on or near the animal and pull the trigger. If you need to shoot quickly, then you just need to shoot mil dots.”
“If you get a 7- or 8-inch twist in an AR, a computer program to match the bullet to the mil dots, then chronograph various loads, you can find a combination that will match the optics,” Cook said. “When they hit the magic velocity they start matching up to the mil dots.” The highest B.C. .224 bullets are too long to work through the magazine of an AR, so the shooter will be relegated to hand feeding single rounds. It’s a trade-off, but worth the effort for precision long-range kill shots.
Always budget conscious, Cook recommends and uses a Bushnell 3200 elite in a 5x – 15x mil dot tactical scope for about $380. (Author’s Note: Bushnell offers a similar mil dot tactical scope today.) “It’s game warden tested,” he said. “It’s been hauled around in our trucks over rough back roads and still holds its zero.” The “budget” custom bolt-action rig Cook favors is a Savage or Stevens bolt-action with an Accu-trigger. Then he mates that with a Brux Barrels bull barrel with a 1-in 6 1/2-inch twist chambered in .223 Remington. All told, this package will come in around a grand. And, as stated earlier, you can have a Brux Barrels custom AR barrel with a 1-in-6.6-inch twist added to your favorite AR-15 and get excellent long-range results, too. Military and tactical-type scopes have mil dots on both horizontal and vertical crosshairs so they can measure height as well as width of an object to estimate range. In addition, the mil dots on the horizontal cross hairs can be used to adjust for windage.
As a secondary function, the mil dots on the reticle can be set up as aiming points to compensate for holdover and wind drift, when you combine it with a laser rangefinder. With particular bullets driven at a specific starting velocity they line up nicely with the mil dots in 100-yard increments.
In practical use, if you have a starting velocity of 2,800 fps and a B.C. of about .500 the drop values at each 100-yard increment line up well with corresponding dots and post between 300 and 700 yards without dialing in additional drop. A shortcut for distances beyond 600 yards can be achieved by dialing in drop from the 4th mil dot instead of from the crosshair. This will save you time and many clicks in adjustment.
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