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Cover versus concealment – the crucial difference

DSTO is conducting trials on the ability of various kinds of cover available to infantry in combat situations (such as the walls of buildings) to provide protection against fire.

Trial personnel setting up photography equipment

The request for the work came from the Australian Defence Force (ADF) Combat Training Centre (CTC), which had found that ADF personnel were often unable to use their weapons to full effect against enemy forces positioned in various kinds of shelter, and conversely, make best use of such kinds of shelter themselves. 

Many personnel were not sure of the difference between ‘concealment’ in which they were hidden from view but not necessarily protected from fire, and ‘cover’ in which they were both concealed and protected. 

In December last year, DSTO researchers conducted the first of two trials to investigate these aspects of combat at the Proof and Experimental Establishment at Port Wakefield, South Australia. The trial team also included personnel from the Army 3rd/9th Light Horse as well the Royal Melbourne Institute of Technology and Vision Research. The role of Trial Director was jointly undertaken by DSTO’s Carmine Cauputo and Matthew Smith.

Carmine Caputo says, “The small arms weaponry and the kinds of shelter used in the study were generally typical of those in the close-quarters urban engagement scenarios that ADF forces may encounter during service in the Middle East and East Timor.”

A mix of weaponry and trial targets

The weaponry selected for the trials included the AK47 assault rifle (7.62x39 mm round) commonly used by armed forces and militias in many countries overseas, and the Mag58 general purpose machine gun (7.62x51 mm round) and Austeyr assault rifle (5.56x45 mm round) used by the ADF. 

The type of shelter being tested in this first trial consisted of single cavity brick wall, constructed of 4 kg red-clay bricks with a 70 millimetre cavity. Eight of these walls were constructed for the trial, painted yellow so that bullet impact marks would clearly show up as black streaks or exposed red brick.

A series of 15 to 30 rounds were fired at these walls from a distance of 50 metres, aimed at angles from 5°, 15°, 30°, 45°, 60°, 75° and 90°. The trial process as well as outcomes were recorded on digital stills and video cameras.

The photography setup for the trial was a major logistical undertaking, involving high-speed cameras with very large telephoto lenses, and the use of mirrors to provide views in the line of fire without exposing equipment to possible damage. The photography gear overall had to be sheltered from the elements, and that placed in front of the firing position had to be protected against flying fragments as well.

Part of the trial preparations involved constructing a ‘soft’ rifle mount for remote firing of the AK47. A meteorological station was also set up to provide data about surface wind direction and speed.

Studying the lethality of the ricochet effect

One part of the trial examined the lethality of the ricochet effect, involving a series of firings at the five selected angles from 5° to 60° onto a brick wall, with the ricocheting bullets impacting black-painted panels known as ‘witness screens’ set up at right angles to the wall.

Some witness panels consisted of a single sheet of one-millimetre thick aluminium, while others were composite packs. The degree of damage caused by the ricochets to these screens gave a measure of the likely severity of injuries that personnel would have sustained.

Some impacts left neat holes, while others, caused by rounds tumbling on their long axis, created long tears called keyholes. Some caused multiple impact points after the round fragmented on impact with the wall.

The ricochet effect was also studied using a gelatine torso placed at the edge of the wall to catch the projectile fragments at a 15° impact angle, exposed to rounds from the Austeyr and AK47 weapons.

The two torsos presented for testing were made of a 20% strength solution of gelatine jelly, which, at a temperature of 12°C, is known to have a consistency like that of human tissue, making it usable for studies of the severity of damage sustained by a human body when subjected to impacts of various kinds.

Optimising torso performance

Presenting the torsos for trial involved a high degree of coordination between the various teams involved in the firing exercises in order to ensure that they were at the correct temperature – neither too cool nor too warm – when firing was carried out.

Before the trial, the torsos were kept in refrigerated storage at 10°C in plastic wrap to maintain their consistency at close to the required temperature. After placement on the firing range with the wrap removed, their temperature was monitored with a removable thermometer to determine when they had attained the requisite 12°C through warming from ambient heat.

To assist with photo recording of the trial, the torsos were illuminated by a light from below, causing the translucent yellow gelatine mass to glow internally, while another spotlight was trained on the side to further boost luminosity. The purpose of applying these lights during the trial in what was already strong summer daylight was to raise light levels adequately for the capture of high-speed video footage shooting at up to 7,500 frames a second.

At these speeds of video capture, the journey of the bullet, travelling at approximately 900 metres per second, could be clearly seen as it ricocheted from the wall and impacted the torso.

Two high-speed cameras were used as a pair, positioned 3 metres apart and 50 metres from the target, to provide a stereoscopic view of the trials. By combining matching frames from both cameras, researchers have been able to generate three-dimensional images of the bullet strikes on a torso to gain a measure of the depth of penetration caused by each projectile type.

Penetrative power put to the test

Trials were also carried out to test the penetrative effect of rounds on shelters. The rounds were fired from a distance of 50 metres at 75° and 90° to the target materials.

Results of these tests showed that a seemingly impenetrable solid object, such as a double brick wall, will only provide temporary shelter against today’s high-powered infantry weapons.

Single-shot fire, with its pin-point precision accuracy, was shown to be far more effective in this regard than automatic fire where shots spray across a much greater area.

Trial outcome resources

Carmine Caputo says, “Looking at the photographic materials we obtained, the trial was clearly a huge success. It was made possible by the photographic technologies that enabled the capture of trial results at a distance.”

The photographic resources generated will be used to create an educational package for CTC staff to enhance their judgment when adjudicating training engagements. Video images and stills will be provided for trainees to demonstrate the real effects of small arms fire on various forms of shelter.

The photos are also being used for research on the performance of small arms weapons and their impact on various kinds of targets.

A second trial planned for later this year will carry out further studies on the effects of small arms on a range of other materials including reinforced concrete slabs, steel plates, sandbag walls, weatherboard, plasterboard, corrugated iron, earth mounds, timber, dense foliage, rocks and rubble and body armour.

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