Test Report No 3
An investigation into the backsplash from bullets fired directly into various surfaces.
R S Taylor, S Bryce, Aintree Shooting Services Ltd, Liverpool.
A series of different bullets were fired through three paper screens into a vertical sheet of armour plate steel, the sheets were then examined to ascertain the risk to the firer of fragments returning along or near to the line of fire.
Bullets were then fired through a hardboard sheet into the damaged area of the steel target and into a concrete target.
In the design of indoor ranges it is a requirement that any surface within 12° of the line of fire and normal to it, be protected in such a way that any inadvertent bullet impact will not result in fragments of the bullet leaving the building or returning towards the firer (up-range) in a hazardous manner. This report is concerned with the latter requirement. The return of bullet fragments up-range is known as backsplash. A traditional form of protection against backsplash has been to face the surface with 2" thick timber fastened 2" away from the surface.
Apparatus and experimental method :
It was known that side splash from disintegrating bullets was
severe and a small plywood canopy was placed above the main impact
area to absorb the worst effects. This caught fragments leaving
at angles of up to 46° from the plane of the target.
Timber boards were used to protect the floor.
A sheet of lightweight paper was hung above sheet 1 to detect any fragments that might pass over it.
The three cartridge paper sheets were positioned so that the furthest from the target, sheet 3, protected a 3metre wide strip at a distance of 7 yards from the target, this being the closest distance at which shooting is normally done.
Each shot was fired through a chronograph to record its velocity.
After each series, each paper was illuminated from the rear and examined for penetration. The floor was examined for fragments and their positions measured.
B: The steel target was replaced by a 2" thick concrete slab and six 158gr 38sp RNL bullets were fired into it.
C: A hardboard sheet was placed 2" in front of the damaged steel target. Twenty 158gr 38sp RNL bullets and twenty 124gr 9mm FMJ were fired through it into the damaged area in a group approximately 2¾" x 1½".
D: A hardboard sheet was placed 2" in front of a 3" concrete slab and fifteen 124gr 9mm FMJ bullets fired into it.
A: Details of the bullets fired and their velocities (ft/sec) are given in appendix A.
Damage to the cartridge paper sheets in given below.
||5P 8I L/UR||B9 5x357||
||1P 8I LR||B10 5x357||
||11P 16I UL|
||2P 8I UR||B11 5x45ACP||
||3P 2I LR/L|
||1P 2I LL||B12 5x45ACP||
||2P 7I LL||B13 5x357||
||2P 2I LR/L|
||1P 4I LR||B14 5x38sp||
||1P 17I LR||B15 5x38sp||
P - penetration
I - indentation
Quadrants in which damaged occurred as seen by the shooter: UR upper right, LR lower right, LL lower left, UL upper left.
All penetrations were small.
Sheets 2 and 3 were undamaged throughout except for:
B10 sheet 2 4P 2I L/UL
B10 sheet 3 2P 2I L/UL
B11 sheet 2 1I LR
The B9 series damaged the target, making characteristic thumbprint
indentations in the steel, and the small plywood canopy became
dislodged during series B10.
The lightweight paper above sheet 1 was penetrated five times, once each in series B4, B6 and B8, and twice in series B9.
A graph showing the distribution of fragments over the floor is given in appendix A.
B: Six 38sp bullets fired into a 2" thick concrete
The target fractured after the sixth shot.
Sheet 1 extensively penetrated, damage starting a radius of about 5".
Sheet 2 3P UL
Sheet 3 1P LL
The penetration in sheet 3 was a large tear, as was one of
the penetrations in sheet 2. Assuming these to have been
caused by the same fragment, the straight line trajectory between
sheets 2 and 3 was:
21° on plan, from the line of fire, moving to the left of the shooter.
12° downwards vertically from the plane of the firing line and along the line of the trajectory.
Extending the line backwards, there was no equivalent damage to sheet 1, indicating, together with the shape of the penetration, that the damage was probably caused by a large, spinning fragment of jacket.
C: Twenty bullets fired through a hardboard sheet into
the damaged steel target.
38sp: The back of the hardboard sheet was marked with radial streaks of lead starting approximately 6" from the centre of the group, indicating a maximum angle of splash of 34° to the plane of the target. No fragments either penetrated or stuck into the back of the sheet.
9mm: One fragment penetrated the hardboard at a shallow splash angle. The back of the sheet was streaked with lead as for the 38sp but was also scarred.
D: Fifteen 9mm bullets fired through a hardboard
sheet into a 3" thick concrete target.
A crater approximately ½" deep was formed in the concrete. Four fragments penetrated the hardboard. Two landed immediately in front of the hardboard, the other two passed through at an angle of 34° to the plane of the target.
A: Although a large number of fragments were found in the region of floor protected by sheet 3 only two fragments actually penetrated it, possibly due to striking the damaged area of the steel target. It is presumed that the fragments bounced along the floor or flew along eccentric trajectories due to their flattened (frisbee) shape.
B: Even though sheet 1 was extensively penetrated due to the fracturing of the concrete target, only one fragment, on a downward trajectory, passed through sheet 3.
C: This was a particularly severe test but no fragments returned directly towards the shooter. A maximum splash angle of 34° to the plane of the target was noted.
D: This too, was a severe test but, again, no fragments returned directly towards the shooter. A maximum splash angle of 34° to the plane of the target was noted.
This work shows that bullets fragments are unlikely to return towards the shooter after a direct impact with a steel or concrete surface, and that the bulk will be dispersed radially in a pattern which has an angle of no more than 34° to the plane of the target. Further, previous work, (The distribution of energy among fragments of ricocheting pistol bullets. M.A.Houlden. JFSS 1994; 34(1): 29-35), has shown that the total residual energy in bullet fragments after impact at angles as high as 78° is less than 10% of that prior to impact, thus the energy of individual fragments will be low. Backsplash protection to areas that will be subjected only to occasional, accidental impact is thus, arguably, unnecessary.
However, given that actual surfaces may present a variety of profiles and hardness, and that the primary risk to range users is of serious eye damage, it would be unwise to extrapolate this test thus far, (see also, note below). Nevertheless, it is apparent that 2"of timber is excessive. A simple test for the suitability of a proposed material would be to compare the sheets of paper after test-firing the layout shown in the figure below.
This report has not dealt primarily with backsplash from a steel surface damaged by repeated impact, but there is some indication that it is potentially serious, particularly with regard to eye injury. Thus where vertical steel sheets are used as bullet stops, these being easily damaged, robust, preferably self-sealing backsplash protection is essential in front of the main impact area. Further, both the steel and the backsplash protection should be inspected regularly. Notwithstanding this, it is also recommended that where such bullet stops are used, shooters and spectators should wear eye protection.