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.
Abstract :
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.
Introduction :
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 :
A:
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.
Results :
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.
|
|
|
|
|||
B1 5x38sp |
|
5P 8I L/UR | B9 5x357 |
|
undamaged | |
B2 5x38sp |
|
1P 8I LR | B10 5x357 |
|
11P 16I UL | |
B3 5x38sp |
|
2P 8I UR | B11 5x45ACP |
|
3P 2I LR/L | |
B4 5x38sp |
|
1P 2I LL | B12 5x45ACP |
|
undamaged | |
B5 5x9mm |
|
2P 7I LL | B13 5x357 |
|
2P 2I LR/L | |
B6 5x9mm |
|
1P 4I LR | B14 5x38sp |
|
2P LL | |
B7 5x9mm |
|
1P 17I LR | B15 5x38sp |
|
1P LR | |
B8 5x9mm |
|
undamaged |
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
target.
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.
Observations :
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.
Conclusions :
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.
NOTE
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.