Methodology of Digital Firearm Ergonomic Design

Abstract

This paper describes a methodological human centered approach during handgun design. For evaluation of reach distances to handgun controls (trigger, slide stop, magazine catch) a digital human models and ergonomic software were used. With these digital human models a variety of minimal, maximal and average reach distance for Americans, Europeans and Asians were proposed. Distances for American and European population were used for creation of a handgun functional sample. Test shooting performed with this functional sample was evaluated by a questionnaire which was filled by 18 male members of armed forces. These responses evaluated the suitability of functional sample and identified specific parameters for future improvement.

Full text

Methodology of Digital Firearm
Ergonomic Design
Marek Bures, Tomas Görner, Antonin Miller and Martin Kaba
Abstract This paper describes a methodological human centered approach during
handgun design. For evaluation of reach distances to handgun controls (trigger,
slide stop, magazine catch) a digital human models and ergonomic software were
used. With these digital human models a variety of minimal, maximal and average
reach distance for Americans, Europeans and Asians were proposed. Distances for
American and European population were used for creation of a handgun functional
sample. Test shooting performed with this functional sample was evaluated by a
questionnaire which was filled by 18 male members of armed forces. These
responses evaluated the suitability of functional sample and identified specific
parameters for future improvement.
Keywords Handgun Digital human models Specific populations Ranges 
Grips Virtual models
1 Introduction
Each tool used by a man need to be suitable for use and also designed in the way
that doesn’t endanger the user. The product ergonomics is the field that deals with
those issues. This paper is mainly focuses on the field of firearms especially
handguns. Mainly armed forces (army, police, etc.) come into contact with guns
M. Bures (&)T. Görner A. Miller M. Kaba
Department of Industrial Engineering and Management, University of West Bohemia,
Univerzitni 8, 30614 Pilsen, Czech Republic
e-mail: buresm@kpv.zcu.cz
T. Görner
e-mail: tgorner@kpv.zcu.cz
A. Miller
e-mail: amiller@kpv.zcu.cz
M. Kaba
e-mail: kaba@kpv.zcu.cz
©Springer International Publishing Switzerland 2017
M. Soares et al. (eds.), Advances in Ergonomics Modeling, Usability & Special
Populations, Advances in Intelligent Systems and Computing 486,
DOI 10.1007/978-3-319-41685-4_20
221

nearly every day. For this reason these weapons must be adapted to fit in the hand in
the best way. Also the firearms must be maximally reliable during shooting.
There are several areas of firearm design that have been the subject of previous
researches. Hancock et al. [1] discussed the issues in firearms design. They stated
that the need for ergonomics firearm improvement has never been greater. Among
their observations, trigger pull, hand grips, sighting devices, and safeties are among
the critical components of firearms whose ergonomics have not been studied, nor
have their interfaces been standardized.
Previous studies regarding shooting performance have focused mainly on pos-
tural stability and its impact on shooting accuracy [2–5]. Several researchers
investigated the effect of rifle length and weight on shooter stability. The concept of
weight reduction in rifle design has long been emphasized. Larger aiming fluctu-
ations occur with heavier rifles because heavier rifle weight increases upper
extremity loading, which increases the center of pressure fluctuation of the
shooter-rifle system in the transverse axis [6]. In addition, Kemnitz et al. [7]
examined the effects of gender, rifle stock length (17.8, 22.3, and 26.2 cm), and rifle
weight (3.2 vs. 3.8 kg) on military marksmanship performance. There were no
significant differences in either measure of marksmanship performance as a function
of sex. Marksmanship precision was significantly better with the lighter rifle.
Results of [8] also revealed that reducing rifle weight was one of the most important
factors of rifle redesign. Other researchers studied the influence of muscle tremor [9,
10] or felt recoil on shooting performance [11]. Results from all these studies
showed that rifle design has an impact on posture and muscle activation. Designs
that were heavier and longer caused more shooter fatigue during aiming and were
significantly less-stable and less-preferred among participants.
Another area of discussion leads to configuration types. There is broad dis-
agreement on whether a bullpup rifle configuration, which is typically lighter,
shorter, and has its center of gravity located closer to the user, is objectively better
or worse than a conventional configuration rifle from a usability and performance
standpoint. From the studies of [6] and [12] according to the stability and perfor-
mance analysis the bullpup weapon designs were found to provide a significant
advantage, even while subjects showed considerable preference toward the con-
ventional weapons.
Nearly all of the previous studies focus primary on rifles and so few studies have
been performed on handguns. This paper focuses directly on handguns design
however the principles and methodologies can be widely utilized also for the rifles.
Also the importance of firearms operators isn’t much discussed however Cornell
et al. [13] focused on comparison of firearm safety mechanisms. The results from 30
experienced subjects showed that safeties whose actuators were mounted within
easy reach of the trigger finger were preferred.
The objective of the paper is to present a methodology using human-centered
design during the development stages of the new handgun model. Today the
information technologies are perceived as an indispensable tool in the design of a
new product. Possibility to verify product parameters and suitability for user in
computer virtual reality before functional prototype is absolutely undeniable.
222 M. Bures et al.

For this purpose a digital human models (DHM) are used to evaluate the suitability
of the design according to anthropometric parameters of the users. These DHM are
fully customizable, so that results of studies carried out are perhaps the most
realistic. If we talk about customization of a DHM, we mean setting its gender,
nationality, percentile or specific body measurements, so that our digital human as
much as possible corresponds to specific user. With user defined like this we then
have the possibility to perform a variety of ergonomic analysis. We can find out
how users (from different population size) will perform a given task, analyze the
risk of injury, needed power, reach, grips and many other factors.
2 Methodology
Standard progress in the new firearm development consist of two phases, prototype
development and production preparation as described on Fig. 1. Our methodology
supports the development phase.
Prototype development phase consist of three main activities. First there is a
conceptual design. Within this activity the development team must firstly create a
concept of the chosen solution supplemented with sketches, calculations and sim-
plified assemblies. The second activity is a creation of functional sample. Technical
implementation of the new product, which verifies principal solutions especially in
terms of functionality of individual parts or all assemblies of the new product, is
developed. Functional sample is made on the basis of the design documentation.
Construction, design, and material integrity may differ from the final product. The
third and last activity in development phase is the creation of the prototype.
Fig. 1 Phases and activities during firearm development
Methodology of Digital Firearm Ergonomic Design 223

The prototype represents technical design of a new product, which matches in terms
of construction, materials and functionalities with the final product. The prototype
is created in order to test all firearm functions, operating features and safety aspects.
Production preparation phase consist of two main activities which aims for the
start of serial production. First activity is introduction to production. The goal is to
verify the proposed manufacturing processes of a new product and both technology
and production equipment that will be used in mass production. In this stage the
production of molds and complete tools for serial production is performed. The
second activity is the test series where the production runs as in the serial pro-
duction for some time. The final adjustments are performed.
2.1 Conceptual Design
For analysis and development of new handgun model from the ergonomic point of
view the software Tecnomatix Jack and its digital human model was used. This
software ranks among the best in its category. Tecnomatix Jack (Tx Jack) contains
several anthropometric databases so it is possible to compare firearms models for
different populations. Based on these results we can say, what suits and what is
appropriate to change. In our ergonomic analysis of a handgun we focused mainly
on the suitability of the controls location (trigger, slide stop, magazine catch) and
the way of handgun grip. The goal is to ensure maximum comfort during handgun
using and also elimination of adverse effects on the user which related to safety use.
Each weapon should be suitable for the widest number of users. Therefore three
populations were chosen for analysis [14]. American population was represented by
ANSUR database [15], European population by German database [16] and Asian
population by Korean database [17]. For each population analyses were carried out
for three different sizes of statures thus hands, namely for 5th, 50th and 95th
percentile. Furthermore the anthropometry survey of Czech population was per-
formed [18]. Those data were inserted in the ergonomic software TX Jack so DHM
representing Czech population was created.
2.2 Functional Sample
After conceptual design a functional sample was created according to the design
documentation. Functional sample was made with the technology of 3D printing
and was used subsequently for test shooting. The final suitability and user satis-
faction was approved by questionnaire of user satisfaction during the test shooting.
A total of 18 male subjects participated on test shooting. The mean stature was
177 cm (range, 170–182 cm), mean body weight was 83.5 kg (range, 76–95 kg)
and mean age 44.8 years (range, 38–54 years). All subjects had considerable
experience and were members of armed forces (police or military). All subjects
224 M. Bures et al.

were healthy and reported no musculoskeletal problems or cardiovascular diseases
that could be detrimental to physical performance. The purpose of the questionnaire
was explained before test shooting as well as individual questions. The question-
naire consists of 33 questions structured in three groups as follows.
1. Technical parameters with ergonomic influence—evaluated were parameters
like trigger (reach, pool, shape), reset length, trigger guard shape and size; grips
(frontal side, back side, side grips, materials), magazine length, manipulation
with slippery hand; operators reach and pressing (slide stop, magazine release,
safety).
2. Technical parameters and utilization—evaluated were parameters like firearm
loading and unloading, stiffness of the main spring, cartridge indicator visibility,
sight.
3. Handgun favorability—overall handgun design, overall handgun shooting
performance.
Rating of individual questions was performed via a 5-point scale similar to
school grades: (1) very suitable, (2) suitable, (3) neutral, (4) unsuitable, and (5) very
unsuitable. The assistant was asking shooter the predetermined questions related to
the areas of assessment and wrote down the results in order to record the score and
also the subjective feelings of the shooter. Finally the assistant repeated the areas of
assessment and scores to the shooter thus the shooter had the possibility to revise
his decision.
The test shootings took place in one day on an indoor shooting range so that no
weather conditions would affect the shooter performance. The shooting was per-
formed on the distance of 10 m. There were 3 handguns available for testing—the
newly developed functional sample, the predecessor and a direct competitor. Each
subject fired 15 shots from each of the three handguns. There were two scenarios.
One was focused on aiming and performing a precise shooting, the other one was
quickly as possible with drawing from the holster.
3 Results
3.1 Conceptual Design and Digital Human Models
Utilization
The DHM were used for design of handgun controls. As stated before, three
populations (American, European and Asian) were used. During our comparison of
German and Czech hand anthropometry we found out very small differences. There
was in most cases (percentiles and dimensions) achieved almost perfect match with
maximal difference of up to 3 mm. Greater differences were observed only for
females at 95th percentile of the hand length, where Czech arms were shorter by
5 mm. In the case of males, the length of the Czech palms for the 5th percentile was
Methodology of Digital Firearm Ergonomic Design 225

shorter by 4 mm. The largest differences at all were identified for the male hand
circumference, where the Czech hands were in the case of 5th percentile greater by
4 mm, in the case of 50th percentile greater by 8 mm and in the case of 95th
percentile greater by 9 mm. This diameter, however, could be distorted because of
the measured sample, which contained large shares of males working in production,
where there is a greater assumption for more muscular hands [18]. From these
results we can assume the suitability for Czech as well as German population. Also
the analyses of American hand dimensions revealed not very big differences.
After verifying the suitability of anthropometric databases we advanced to
analysis of optimal reach limits of the handgun controls. For the individual per-
centiles of each population the ranges on trigger, slide stop and magazine catch
were evaluated as displayed on Fig. 2. The main criterion was the length of index
finger and thumb. When evaluating the reach on trigger we also considered care-
fully the position of index finger on the trigger during shooting. Ideal position of the
trigger should be in the middle of the last phalange of index finger as visualized of
Fig. 3. Any other position will result in pulling the handgun either to the right or
left side during shooting.
With ideal position in mind we have measured the distances for the trigger. The
distances were measured from the rear side of the grip plate in other words from the
place where base of the thumb came in contact with handgun grip as displayed on
Fig. 4. The same procedure was selected when measuring the reach distance for
other controls. All distances are summarized in Tables 1and 2.
Fig. 2 An example of digital human model with tested handgun
Fig. 3 Visualization of
different trigger positions (left
side wrong trigger position,
right side correct trigger
position)
226 M. Bures et al.

Three population groups have been evaluated. The first group consists of
American and European males, second group is composed of American, European
and Asian males and the last group represents also females of all three populations.
The minimal and maximal distances represent 5th and 95th percentiles. Also it must
Fig. 4 Distances in measurement of handgun controls
Table 1 Reach for trigger
Minimal distance
K (mm)
Average distance
K (mm)
Maximal distance
K (mm)
Male America + Europe 64.5 69.5 74.5
Male America + Europe +
Asia
61.5 67.5 73.5
Male and female America +
Europe + Asia
56 64 72
Table 2 Reach for magazine release button and slide stop
Minimal distance
L (mm)
Average distance
L (mm)
Maximal distance
L (mm)
Male America + Europe 41 46 53
Male America + Europe +
Asia
38 44 50
Male and female America +
Europe + Asia
33 44 50
Methodology of Digital Firearm Ergonomic Design 227

be emphasized that those distances are ideal (from the basic position) which means
that there is no need to regrasp the handgun. As can be seen the data dispersion rise
with wider population spectrum. Ideal handgun can’t be created. Those differences
must be adjusted for instance by changeable grip parts.
3.2 Functional Sample and Test Shooting
Males have the majority in armed forces so the first functional sample was created
according to the male’s dimensions of American and European population. After
the test shooting the responses have been analyzed and evaluated. Questions
respectively parameters evaluated with worst grade than 3 have been investigated in
more detail in order to improve them in future design. The questionnaire results
from all three tested handguns are summarized in Table 3. Regarding the trigger
and grips evaluation the functional sample ranked as the best before predecessor
and direct competitor. The reach on operators was ranked on the direct competitor
as the best. This was due to the fact that these questions contained also the amia-
bility regarding the operators pressing. Bad shape and thus the force needed to press
the slide stop worsen the rating of the functional sample. In the area of technical
parameters and utilization the functional sample had slightly worse rating than the
competitor however in the overall handgun evaluation the functional sample was
the best. This also shows the average values for the ergonomic evaluation, average
Table 3 Test shooting survey responses
Predecessor Direct
competitor
Functional
sample
Technical parameters with
ergonomic influence
Evaluation of trigger 2.47 1.72 1.67
Evaluation of grips 2.15 2.18 1.38
Evaluation of
operators reach
2.15 1.88 2.11
Technical parameters and
utilization
Evaluation of
technical performance
2.19 1.75 1.82
Handgun favorability Overall evaluation of
the handgun
2.50 1.92 1.50
Average evaluation Average of ergonomic
evaluation
2.26 1.93 1.72
Average of
ergonomics and
utilization
2.24 1.88 1.74
Total evaluation of the
handgun
2.29 1.89 1.70
228 M. Bures et al.

values of ergonomic evaluation together with technical performance and total
evaluation of the handgun.
4 Discussion
Any equipment used by a man should be compatible with physical characteristics.
Anthropometry, as a science that’s deals with measurements of the size, weight and
proportion of the human body, is suitable for this kind of optimization. Mismatches
between human anthropometric dimensions and equipment dimensions are known
to be a contributing factor in decrease productivity, discomfort, accidents, injuries
and cumulative traumas [19,20]. Hand anthropometry data are essential for handles
design, griping options or distances on control buttons. Many aspects must be taken
into account such as nationality, gender of the operating person, dominant hand or
age group. However no tool is perfect for every user. Anthropometry can still be
considered as the key for any attempt to resolve the dilemma of fitting the tool to the
human. Designing for humans or human-centered design should improve safety,
increase comfort, increase user acceptance, and reduce fatigue and stress.
Research regarding the firearm design focus basically on rifles as a main part of
military equipment. Primary attention is given to the effect of rifles weight and length
on shooter postural stability and shooting accuracy. Handguns as a backup weapon
are being missed out. However regarding the police forces and shooting enthusiastic
the handguns are the most popular. This paper focused on the area of handgun
operators design and especially the distances. The digital human models and virtual
handguns models were used to evaluate new methodology of digital ergonomic
design. Recommended distances on handguns operators for three different popula-
tions have been stated. For instance for the combined population of American and
European males the minimal distance of 64.5 mm, average distance of 69.5 mm and
maximal distance of 74.5 mm for the trigger was stated. This is in conformity with
US patent 008151504B41 [21] where minimal distance for the trigger is 65 mm,
average distance is 70 mm and maximal distance is 75 mm. The suitability of those
distances and distances to other handgun operators was confirmed by a functional
sample which design was evaluated during test shooting by a questionnaire.
5 Conclusion
The study presented by this paper was the first attempt to utilize digital human
models as a tool for human-centered design of a handgun. The results showed that
these digital human models can serve for very accurate design of reach distances on
handgun controls. Validation was performed by functional sample created with 3D
printing method. Although the methodology was validated on handgun there is a
wider utilization on rifles and any firearms.
Methodology of Digital Firearm Ergonomic Design 229

Acknowledgments This paper was created with the subsidy of the internal grant
SGS-2015-065-Developing sustainable production system parameters carried out with the support
of University of West Bohemia.
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