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Parallel Thumb Placement

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By Guy Sagi

It may be the result of a death grip on a precision rifle’s wrist, sympathetic movement as the trigger finger begins its press or torqueing during the process, but your famously opposable digit could be doing you a disservice at distance and there’s a scientific reason.

Whether you are behind a not-so-gracefully aging rimfire or a sleek and modern high-caliber tack driver punching tiny groups of holes in paper—regardless of distance—it’s the simplest and purest form of shooting pleasure. It means you’re doing everything right, the ammunition choice was a wise one and the firearm is performing properly.

Of course, we all wish we could deliver those shots with a little more precision, and a few years ago, an instructor at SIG Sauer Academy gave me a tip that helped significantly. I wasn’t a bad shot at the time, but he diagnosed a nasty habit immediately, and once it was remedied, my groups shrunk by at least .1 MOA—actually more. One tenth of an inch at 100 yards may not sound like much, but the number of “flyers” I suffer has also gone down, I’m a lot more consistent and ammunition was the only investment required to improve.

To understand how the slight movement can result in a miss, assume you have a one-yard-long barrel (just to make the math simple). If the back is anchored solidly as you delivered the shot, but the front moved by only 1/10 of an inch to the left, by the time the bullet reaches 100 yards it will be 10.1 inches left of the bullseye.
To understand how the slight movement can result in a miss, assume you have a one-yard-long barrel (just to make the math simple). If the back is anchored solidly as you delivered the shot, but the front moved by only 1/10 of an inch to the left, by the time the bullet reaches 100 yards it will be 10.1 inches left of the bullseye.

All he did was move my thumb position when I settled into the gun and shot. Perhaps I was holding it across the stock’s wrist at a white-knuckled pressure hoping to avoid scope eye if the gun turned super hero and leaped from the bench, or he may have seen a slight shift in the gun as I pressed the trigger. I’d like to think the latter because my support arm never touches the rifle when working long distance.

Don’t jump to the conclusion that changing your thumb placement will miraculously make you a world-class long-distance shooter. It may help, but as this Gunsite instructor demonstrates, the rest of your body has roles to play as well, and each can enhance performance.

Either way, I now place my dominant-side thumb very lightly on the side of the stock, pointed in the direction I’m shooting—not wrapped around the wrist toward my support side—which minimizes its ability to apply pressure. As a bonus, it’s reduced the amount of stock the base of my trigger finger encounters when engaged (so-called wood scraping). This may be peculiar to my hand and stock sizes, but my finger’s entry into the triggerguard is also more perpendicular than oblique, yet another side effect that makes travel a little more buttery smooth.

This instructor at Gunsite placed his thumb on the tang position and it worked extremely well for him as he engaged targets well beyond 1,000 yards with a .338 Lapua Mag. Weatherby.

You may think you’re immune to any thumb-induced pressure during firing, like I did, but there’s some science that disagrees. A study published in the Nov. 15, 2000, Journal of Neuroscience, called “Quantifying the Independence of Human Finger Movements: Comparisons of Digits, Hands, and Movement Frequencies,” explains, “We found that even when asked specifically to move one digit without moving any other digits, normal human subjects produced low-amplitude motion in noninstructed digits simultaneous with the large-amplitude motion of the instructed digit.” The good news is the index finger, thumb are the most independent from the phenomena, and the slower the deliberate motion (trigger press), the less pronounced the communication misfire was.

It’s easy for armchair quarterbacks to dispense advice, but this competitor during a sniper competition on Fort Bragg makes it obvious there’s more one way to hold your thumb when taking a long shot. If his tang position wasn’t working well, he would never have qualified in this world-class field.

The muscles, tendons and cartilage that run the show are also in very close proximity and often interconnected, too. “Limited independent flexion of the thumb and fingers in human subjects,” which was printed in a 1994 edition of The Journal of Physiology, identified some of that and even dissected cadavers to measure proximity and adjoining tissue. Its discussion section sums things up pretty well with: “The present study has shown that human subjects have a limited ability to contract selectively ‘muscles’ which flex the distal interphalangeal [that’s fingers and thumb] joints of the digits.” There is an obligatory coactivation of other deep digital flexor muscles: this coactivation increases when the digit flexes at a greater velocity or through a larger angle.”

With the thumb remaining on the side of the stock, it minimizes the chances of it moving the stock during the trigger squeeze. Checkering on this Kimber provides it a nice tactile index to keep the thumb close to the safety above.

It may be common sense that an index finger and thumb accustomed to years of grabbing things with tweezer-like precision instinctively move together, even if imperceptibly, but this pair of studies add a sound scientific foundation to the belief. Both also make a great case for slow trigger presses and even a good argument for a match-grade trigger with the observation that the heavier the weight being lifted by a finger, the greater the movement/pressure in adjacent digits.

Some very good shooters place their dominant-hand thumb on the rifle’s tang. This position minimizes side-to-side shift transmitted by the digit, and on some rifles allows the marksman to ride the safety. However, the position is not possible with all guns.

Can it really make a big difference? There are many other factors at play, but a theoretical rifle with a 36-inch barrel puts the question into perspective. Attach the back of the barrel to an unmovable anchor and put the crosshair on a bullseye 100 yards away. If, as you squeeze the shot, the muzzle end somehow moves .01 inch (that’s 1/100) left, the hypothetical bullet will be slightly more than one inch off target at that distance. The math works out to be error per yard (.01/yard, which was the barrel length for simplicity) times yards traveled (100), plus initial error (.01 inside the barrel), or 1.01 inch. It’s already not shooting MOA, but add that tiny error to the right on the next shot and you’ve doubled the two-shot group and the gun is probably out to permanent pasture.

With the thumb remaining on the side of the stock on this 1895 Chilean Mauser, it minimizes the chances of it moving or applying pressure to the stock, and ensures the clean engagement of the trigger with the index finger without touching any wood.

Both of the studies found the amount of inadvertent adjacent finger and thumb movement varied widely among test subjects, and the latter also found that in all but one test subject, involuntary movement reduced with repetition (we call that practice). That fact was on display hundreds of years ago with serious guitarists and piano players, who also face the finger co-movement challenge. Successful ones practice and exercise their way out of it.

With the thumb placed across the rifle’s wrist, the trigger finger’s angle of entry can change slightly, which in turn can increase perceived let-off weight due to rubbing the stock as it squeezes. The affect, termed “dragging wood,” can have an adverse effect on accuracy.

I know some great shooters who have done the same today. There are those who stay with the wraparound technique and regularly outclass me during shooting seminars (a few play the piano well, coincidentally). Others ride the tang with great success, although I don’t like the fact it won’t work on every rifle in my safe. Most of them are at long-distance events a lot more than I am, though, so I’m content with a simple approach that cheats a heavy practice schedule and remedies my bad habit.

Thumb placement on the tang isn’t always a workable solution, especially on older rifles, like this 1895 Chilean Mauser where it could wind up riding the bolt’s cocking piece when it’s ready to fire.

All three of my oldest grandsons learned to shoot a rifle with this technique, unlike the way I was taught with a tight, wraparound hold. Two of them are currently in the U.S. Army. One has already served in the Sand Box as a designated marksman, the middle one was second in his basic class in marksmanship, and the third, currently in ROTC, earned the nickname “The Assassin” at the range from his classmates (as a freshman).

It does not work well for everyone, but I wish I had met that wonderful instructor years before. I’ve seen the results when shooters start this way early, and it’s amazing.

The same technique won’t work on pistol-gripped rifles, although avoiding a death grip is still key to consistently hitting distant targets (photo courtesy of DPMS).

The next time you’re at the range with a traditionally stocked rifle, give it a whirl. You may be as pleasantly surprised as I was after 40 rounds, and if nothing else, really impressed at how it gets young shooters on target, and excited about the next range session.

All photos by Guy Sagi (except photo courtesy of DPMS).

Guy Sagi

Guy J. Sagi has been reporting on the outdoors for more than 30 years. He was editor in chief of Shooting Illustrated, the NRA’s newsstand monthly, NRA InSights, Shooting Sports USA and Free Hunters during his 10 years with NRA publications. His byline has been seen in most major outdoor publications and he was editor in chief of Safari Times, Safari Club International’s monthly, for decade. The author of Fishing Arizona and Hunting Small Game in Arizona also has of 15 years of search and rescue experience with a Mountain Rescue Association-affiliated organization in Arizona.

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