Making the Shot
The Physics of Shooter Grip and Trigger Techniques in Handgun Aiming
John Dike
951-256-0123
dike@usc.edu
University of Southern California (University Park Campus)
Abstract:
No handgun gripping or trigger technique is universally agreed upon, even though
firearms have been in existence for hundreds of years. The purposes of this paper are to
examine common gripping and trigger errors which create forces that can negatively affect
projectile accuracy, and to determine corrective physical moves to increase precision. A
gripping style will be suggested to maximize normal forces and minimize operator error. These
purposes will be examined through the use of simple force analysis.
Multimedia Suggestion: Video of application of other grip style and suggested style with target
comparison.
John Dike (Norco, CA) is a junior at the University of Southern California studying Industrial,
Systems, and Information Systems Engineering. He is an Air Force cadet and has pistol training
with the US Air Force, Anaheim SWAT and private companies.
Keywords: handgun, grip, trigger control, normal force, aim, accuracy
Making the Shot
The Physics of Shooter Grip and Trigger Techniques in Handgun Aiming
Handgun Basics:
Handguns are an integral part of warfare, peacekeeping and self-defense [1]. Their
purpose, just like any other firearm, is to deliver a projectile to a precise location, referred to as
the "target." If a bullet cannot be placed on target, then it is entirely ineffective. Handguns are
designed to shoot bullets accurately; human error causes shooting errors and missed targets.
While there are many human factors contributing to shooting accuracy, including stance,
breathing, anticipation and muscle fatigue, the shooter's grip is arguably the most impactful.
While often overlooked, the grip is the only place where the shooter and handgun touch,
thereby creating the most significant influence on accuracy [2]. This paper focuses on proper
human grip and trigger mechanics to achieve effective aiming.
There are advantages and disadvantages for either handguns or rifles, depending on the
shooting goal. Handguns are much smaller than rifles and have a much shorter barrel. This
makes them easier to maneuver, conceal, and carry. In essence, all handguns fire as accurately
as rifles. Any discrepancy in mechanical accuracy is insignificant compared to shooter error.
Rifles are larger and heavier than handguns. This means that, based on Newton's second law,
resistance of a rifle to outside forces is greater than that of a handgun [3]. A similar motion by a
shooter that may cause a rifle shot to miss its target is amplified when shooting a handgun.
The general concept of aiming is universal. Every handgun includes sights; a front sight
and a rear U shaped sight (Fig 2). If properly adjusted, aligning the sights will cause the bullet to
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strike directly where aimed. When viewed from the rear of the handgun, the front post needs
to be centered between the rear sight and the tops of both sights need to be horizontal. This is
the perfect "sight picture" (Fig 3).
Figure 2. Handgun parts.
Figure 3. Perfect sight picture.
Because handgun accuracy is susceptible to human error, they are intended for use at short
distances, up to about 25 yards. Therefore, factors such as wind and distance from target are
generally not a concern. Maintain a perfect sight picture and the shot will be close enough to
the center of the target to be effective.
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Common Accuracy Errors:
Finding the sight picture when first aiming the handgun is simple, but holding the sight
picture steady is not as important when initially aiming as it is when actually firing, when the
bullet exits the barrel. The shooter must keep in mind many factors when aiming a handgun
and firing a bullet. The most common errors can be determined simply by where the shot falls
(Fig 4) [4].
Figure 4. Corrections Chart.
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Right Hand Grip and Trigger Control:
It is important to grip the handgun properly or control of where a bullet hits the target
cannot be ensured (Fig 5). While many theories on the best way to hold a handgun exist, a few
points are constant [5]. For a right handed shooter, the crotch of the right hand should be
seated deeply into the notch underneath the slide. The right index finger will control the trigger
but should be pointed along the bottom of the slide when not firing. The middle finger hugs the
grip and rests on the bottom of the trigger guard, while the remaining fingers hug the grip and
lie touching each other [6]. Opinions on placement of the thumb and left hand vary and will be
discussed later in this paper. Good grip placement will help reduce aiming error.
Figure 5. Proper Grip.
The most studied and discussed action that affects aim is how the trigger is pulled.
Pulling the trigger requires force exerted by the shooter. Because the shooter is only human
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and finger strength and touch sensitivity vary, errors will occur. To maintain a perfect sight
picture, the trigger must be pulled directly to the rear without any force exerted to the left or
right [7]. If it is pulled directly to the rear, the force exerted by the index finger will be negated
by the normal force from the shooter's right hand (Fig 6). The trigger finger force will not
overcome the normal force, and the sight picture will remain as desired.
Figure 6. Trigger finger force and normal force.
When too much or too little pressure is applied to the trigger, accuracy will suffer. With
too much pressure, the index finger curls up on itself and tugs the trigger and the rest of the
gun toward the right hand, forcing the resultant shot to the right of the target. With too little
pressure, the index finger straightens out, pushing the trigger and gun to the left, forcing the
shot to the left [8]. These actions are intensified if the trigger is placed too far right or left on
the trigger finger, respectively (Fig 7). The curling and extending of parts of the finger is natural.
Part of the trick is to find the best placement of the finger on trigger to minimize these motions.
The rest is to choose a grip style that applies forces that best negate these motions.
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Figure 7. Trigger portions of corrections chart.
Natural fluctuations in the right hand grip occur because of the motion of the trigger
finger [9]. Not all joints in the hand move independently. Observe that when the index finger
constricts, so do the other fingers [10]. All three other fingers are also in contact with the
handgun, which means their motion will have an effect. The fingers push on the front half of
the handle, causing a force to the right. Because fingers two, three, and four are below the
center of mass of the handgun, they also exert a rotational force downward. The palm of the
hand also has a tendency to expand towards the inside of the hand due to movement at the
wrist when the index finger is constricted. This movement creates a force to the left. The crotch
of the hand also expands at this time, applying an upward force against the notch beneath the
slide. Together, this is the tightening of the grip while pulling the trigger. The resulting force is a
clockwise rotation about the center of the handle and causes a shift down and to the right,
respective to the target (Fig 8 and 9). Certain grip techniques utilizing the left hand, including
the following suggested technique, can negate these forces.
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Figure 8. Forces of tightening grip.
Figure 9. Tightening grip portion of corrections chart.
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Left Hand Grip:
Now comes the age-old question of what to do with the left hand. While experts cannot
agree on a specific "best" way, it is obvious that the left hand grip needs to counter the force
tendencies of the right hand and not contribute any new directions of force. To oppose these
forces and not apply new or excess force, the shooter's grip must be designed on the
application of normal forces. The average right-handed shooter fires low and left because of
the aforementioned tendencies and resultant force. Conversely, the average left-handed
shooter fires low and right. The following grip style will oppose all of the forces mentioned
above and will be useful for most shooters. A left-handed shooter only has to mirror this
example to achieve the same results.
For this grip style, the shooter will place his or her left fingers over the right fingers on
the handle, mirroring them with respect to the center of the gun, so the second knuckles lie
atop each other and the index finger lies against the bottom of the trigger guard (Fig 5). To
counteract any unbalanced forces from the left fingers, place the left palm along the left side of
the handle. Rather than placing the palm on top of the right fingers, put as much of the heel of
the left hand directly on the gun as possible. Increasing surface area in contact with the firearm,
and thus contact points, evenly distributes normal forces so that no rotational forces occur [11].
Because the left palm and fingers tighten together, they can grip as hard as the shooter desires.
Right and left hand forces will negate each other and will not alter the sight picture. Having a
tight left hand grip over the right hand will create normal force to the left and right and will
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prevent the right hand from moving. So far, this is somewhat standard of left hand grip
variants.
Where this grip differs is in the angle of the hand. With the thumb stretched the entire
way wide, angle the hand down about forty-five degrees so that the thumb is in line with the
top of the left arm (Fig 10).
Figure 10. Left hand grip.
This hand/gun configuration creates multiple benefits. First, the left palm angles in a way that it
naturally fits against the side of the handle, creating more surface contact. Second, the left
thumb can be placed directly along the slide, negating force from too much finger on the
trigger. Do not worry about having the thumb on the slide; the slide will not harm the thumb
and the thumb will not restrict the operation of the slide. As long as force applied by the thumb
is consistent and applied before obtaining a sight picture, it will not hurt accuracy. Any force
applied by the thumb is met with normal force from the right palm. The left palm restricts any
potential resulting rotational force (Fig 11).
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Figure 11. Left thumb force and resulting normal forces.
Third, because the left hand and arm angle are awkwardly opposed to each other, they both
tense up. This tension allows the shooter to resist motions without having to concentrate as
carefully [12]. In addition, because of the tension and the low angle between forearm and
hand, the left hand is resistant to move down any further, restricting the firearm from pointing
lower than desired. This grip style provides normal forces at every possible point of contact and
on maximized surface area (Fig 12).
Figure 12. All left hand normal forces.
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More normal forces means the resulting forces of the right hand are negated and the sight
picture is much more easily maintained.
This simple understanding of forces and the left hand grip's purpose of negating them
can help improve even the most experienced shooter's accuracy. There will always be shooter
error, but by understanding the science behind the most error riddled aspects, gripping and
trigger techniques, shooting like a pro becomes that much easier.
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Bibliography
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2003.
[2] S. Denney. (2011, Apr. 2). Coming To Grips With Grips [Online]. Available:
http://www.officer.com/article/10232631/coming-to-grips-with-grips
[3] B. Crowell, Light and Matter, sec. 4.2, 4.3, 2011.
[4] US Army Marksmanship Unit: Pistol Marksmanship Training Guide, U.S. Government Printing
Office.
[5] D. Spaulding. (2006, Feb. 28). Firearms: Get a Grip - how to hold your pistol [Online].
Available: http://www.policeone.com/police-products/firearms/articles/125513-Firearms-Geta-grip-How-to-hold-your-pistol
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http://cheaperthandirt.com/blog/?p=3977
[7] S. Barnum. (2006). Trigger Pull [Online]. Available:
http://www.chuckhawks.com/trigger_pull
[8] R. King, "Basic Pistol Equipment and Competition," unpublished.
[9]A. Viani. (2009, Dec.). Trigger Weight [Online]. Available:
http://www.ghostinc.com/category/1triggerweight
[10] M. Ayoob. (1998). How to shoot a handgun accurately [Online]. Available:
http://www.backwoodshome.com/articles2/ayoob85.html
[11] J. Dreyer. The Benefits of Custom Grips [Online]. Available:
http://www.bullseyepistol.com/goodgrip.htm
[12] K. Rehn, "Support hand wrist angle," unpublished.
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