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The Shotgun Slug Knockdown Myth

By Dave Henderson

The Shotgun Slug Knockdown Myth

The buck appeared out of the fog, his slow, deliberate gait bringing him toward my stand at a quartering angle. Oblivious to my presence, he was walking with his nose close to the ground in pursuit of the doe that had passed by seconds earlier.

At about 60 yards, the buck stopped and turned slightly, lifting his head to test the air while affording a near-broadside target. Knowing that he wasn’t going to bolt while he sifted the air for the doe’s scent, I took my time and fixed the scope’s crosshairs behind his shoulder, slipped off the safety, and gently pressured the trigger.

Boom!

At the report, the buck hunched, mule-kicked, then exploded in a desperate 30-yard sprint before plowing nose-first into the leaf-covered woodlot floor.

The number of whitetails I’ve taken with shotgun slugs over the last 40 years is crowding triple figures, and the scenario just described is very typical of my experience. The shotgun slug — a hulking, menacing chunk of lead that often weighs an ounce or more — has long been revered as a brush-busting sledgehammer that flattens deer in their tracks.

But the aforementioned field experience tells me that the image just isn’t accurate. It’s not that shotgun slugs aren’t lethal. They just don’t turn out the lights on animals as readily as the public imagines.

Supposedly knowledgeable magazine writers have described a slug’s “knockdown power” as a by-product of “hydrostatic shock.” The image of the huge, blunt slug is, after all, one that gives the impression of power. But those reports are based on assumption rather than experience.

The Shotgun Slug Knockdown Myth
The Brenneke line of slugs is designed to penetrate rather than expand, as evidenced by this slug recovered from a deer.

Where I live, legislators long ago mandated short-range shotguns over the potential next-county lethality of centerfire rifles. I constantly hear opinions from hunters on the lack of performance of modern slugs. Complaints are usually in the form of a certain slug lacking “knockdown power.”

Invariably their complaints are based on the fact that they missed the shoulder. Shotgun slugs, you see, have terrific knockdown power when applied to a structural point in the deer’s skeleton. Plug a shotgun slug’s statistics into any kinetic energy or momentum formula, and you’ll get freight train numbers. But, unlike high-velocity rifle ballistics, those figures don’t mean much if the slug doesn’t hit bone.

The ability of a shotgun slug to level its target is, quite simply, a myth — or at least a statement that requires a disclaimer of “when properly placed.” Out of the scores of whitetails I’ve taken with shotgun slugs, only a handful of non-skeletal hits have produced “in-their-tracks” kills. In the world of terminal ballistics, big and slow is anything but a hammer.

Velocity, you see, is a major factor in “knockdown power.” I’ve probably shot less than half as many deer with my .270 as with slug guns, but the majority of the rifle hits dropped the animals immediately. Most of the slug-hit animals made a short run before collapsing.

Veteran gun writer Don Lewis took a knowledgeable look at “knockdown power” in rifles in the last issue of this magazine. He noted that while lower velocity permits the use of heavier bullets that deliver energy deeper into the animal, you still need sufficient velocity to make the whole thing work. Heavy bullets at very low velocities — the virtual definition of shotgun slugs — simply do not provide shock.

A conventional rifled slug is so slow and bulky that it loses more than half of its energy in the first 50 yards. Think about that.

Ballisticians generally agree that it takes a minimum velocity of 2,000 feet per second to produce hydrostatic shock. Only several slugs on the market (3-inch 12-gauge Winchester Partition Gold and the 12-gauge Hornady H2K Super Mag) reach 2,000 fps at the muzzle, and none approach that figure 50 to 100 yards downrange.

The only times I’ve knocked adult deer off their feet with slugs without striking the vertebrae, skull or shoulder blade have been with the Winchester Partition Gold 12-gauge slug at relatively close range. This leads me to believe that the 2,000-fps minimum for hydrostatic shock may be slightly overstated.

To my way of thinking, hydrostatic shock and its byproduct, the tissue-destroying ballistic phenomenon known as “cavitation,” is what drops animals in their tracks. Stop the vital organs from functioning, and the light switch is turned off. Punch a hole through both lungs, and an animal is likely to run “as long as it can hold its breath,” according to legendary gun writer Jack O’Connor. Pierce the heart, and the animal will run on a surge of adrenaline. But an explosion that renders the heart or lung to tatters causes the system to shut down right then and there.

Cavitation is the destruction of tissue surrounding the actual wound channel. But only high-velocity projectiles cause cavitation.

I spent my adolescence shooting rifled slugs that deformed readily on impact. I graduated to heavier, harder Brenneke-style slugs designed to penetrate rather than expand. With either slug, deer would react to the impact, then make a short run. The difference was that the Brenneke usually passed through the animal while the rifled slug did not.

Subscribe Today!When rifled bores and early sabot slugs hit the market in the 1980s, I was one of the first in line. The early hourglass-shaped Winchester and Federal sabots were extremely accurate out of my Ithaca Deerslayer II’s rifled bore. However, those slugs blew through deer like an arrow without expanding and dumping much energy. The animals did not immediately react to eventually lethal lung hits, and blood trails were very poor.

Today, high-velocity slugs like the Remington Core-Lokt Ultra, Hornady H2K Heavy Mag, Winchester Partition Gold and Platinum Tip are actually controlled-expansion bullets. Rear-weighted with lead cores and copper jackets, they are designed to fly flat, penetrate well and expand once they enter vital areas. But their velocities (below 2,000 fps) make them marginal in terms of imparting hydrostatic shock.

Shotgun slugs are lethal and efficient. But the concept of “knockdown power” is only evident when the slug is placed in the right spot.

Reprinted from the August 2004 issue of Buckmasters GunHunter Magazine

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