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TECHNICAL BRIEFS

Effects of Temperature Changes on the Mechanical and Ballistic Responses in Biathlon Shooting

[+] Author and Article Information
Christelle Grebot

FEMTO-ST, UFR ST de Besançon, Laboratoire de Mécanique Appliquée R. Chaléat, UMR CNRS 6174, Equipe Biomécanique et Mécanismes, 24 chemin de l’Epitaphe, 25000 Besançon, France

Alain Burtheret1

FEMTO-ST, UFR ST de Besançon, Laboratoire de Mécanique Appliquée R. Chaléat, UMR CNRS 6174, Equipe Biomécanique et Mécanismes, 24 chemin de l’Epitaphe, 25000 Besançon, Francealain.burtheret@univ-fcomte.fr

1

Corresponding author.

J. Appl. Mech 74(5), 1037-1041 (Aug 23, 2006) (5 pages) doi:10.1115/1.2712229 History: Received March 30, 2006; Revised August 23, 2006

Background: Biathlon is a nordic sport that combines cross-country skiing with rifle marksmanship. It was reported that standing shooting was significantly affected because skiing exercise usually decreased the postural control of biathletes and increased the shooting time. Another hypothesis that may explain the decrease of one’s shooting accuracy after a cession of cross-country skiing could be linked with mechanical factors. The goal of the present study was to examine the influence of negative temperatures on the trigger mechanism and on the ballistic responses of the bullet. Method of approach: In order to determine the possible variations of the force required for triggering, five biathlon rifles were equipped with strain gauges fixed on the trigger. A thermostat vessel was used to control the temperature changes at room temperature (+20°C)(+68°F) until 20°C(4°F). Concerning the ballistic measurements, eight series of five shots were performed at +20°C(+68°F), at 3°C(+26.6°F), at 10°C(+14°F), and at 20°C(4°F). The shooting precision was assessed by determining the group diameter (GD) and the shooting score (Sc). Results: The results showed that from +20°C(+68°F) until 8°C(+17.6°F), the triggering force was equal to 5N(1.12lb), whereas at 20°C(4°F), a triggering force of 8N(1.8lb) was required. The increase of the triggering force that was found under 8°C(+17.6°F) could be caused by the difference between the coefficients of expansion of the different materials constituting the trigger mechanism. Concerning the ballistic measurements, GD at room temperature was significantly lower (P<0.05) than 3°C(+26.6°F), 10°C(+14°F), and 20°C(4°F). Furthermore, Sc was significantly better at +20°C(+68°F)(P<0.05) compared to 3°C(+26.6°F), 10°C(+14°F), and 20°C(4°F) conditions. Conclusion: It can be supposed that the degradation of GD and Sc could be due to the formation of frost in the barrel and by the difference of the expansion coefficient of the bullet-barrel materials. Consequently, both mechanical responses could partly explain the shooting accuracy impairment observed in negative temperature shooting conditions.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Trigger before (a) and after modification and sticking of the gauge (b)

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Figure 2

Hanging system of the rifle

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Figure 3

Experimental mounting

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Figure 4

Measurement (in mm) of the GD, and the Sc. MGD=mean group diameter.

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Figure 5

Relationship between triggering force and temperatures with five cases of triggers

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Figure 6

Mean values and SD of the group diameter (a) and the shooting score (b) performed at different temperatures. *=P<0.05 compared to +20°C(+68°F); §=P<0.05 compared to −3°C(+26.6°F) condition.

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Figure 7

Graph of retraction of aluminum and steel according to temperature (a) and values of retraction of the different materials constituting the pins and the case of the trigger at +20°C(+68°F) and −20°C(−4°F)(b)

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