The backstop provides the primary impact area for the bullets being fired on a particular range and under normal conditions prevents the bullet form leaving the range proper. An important factor to remember at this point is the construction of an otherwise proper backstop will not necessarily eliminate the requirement to provide for the normal downrange safety fan beyond the backstop for the type of firearm or caliber permitted to be fired. The probability of an accidental (firearm malfunction) or unintentional discharge where the bullet escapes the range without first impacting the backstop must be evaluated and considered in the original range design. This must be reevaluated as the surrounding land use changes.
A major consideration for initial construction is to provide sufficient space for ease of backstop repair and lead recovery. All too often, ranges are constructed allowing for the maximum number of firing points and targets in the shortest acceptable width and distance, but with insufficient space to allow regular maintenance or heavy equipment access to the range firing or target line. Special consideration is to provide sufficient space for maneuverability of heavy equipment between the target line and the backstop.
The best outdoor backstop is a manmade earth embankment or a natural hill of appropriate size and shape that meets the specific requirements of a particular site. Alternative backstops may be used when appropriate earthworks are not available. Preferred backstops include: 1) naturally occurring hills or mountainsides (shaping the slope will likely be required), 2) earthen backstops constructed from clean fill, 3) earthen backstops constructed from broken material (concrete or asphalt) and covered with clean fill dirt, 4) earthen backstops constructed from clean fill and stabilized internally, and 5) fabricated backstops using steel or wooden cribs.
Backstop heights can vary according to the site and use. General dimensions are as follows:
1. Height. A minimum height of 15 feet is acceptable but 20 to 25 feet is recommended. This height is the compacted or settled height. Height should also be consistent with other barriers that may be incorporated into the range design.
A ricochet catcher, ricochet baffle or eyebrow can be installed to reduce the incidence of bullets escaping the range by sliding up the face of the backstop. The ricochet catcher is designed to retain only those ricochets that occur on the face of the backstop. While the distance traveled by such a ricochet would be nominal, this factor will nevertheless need to be included in the design calculations. These devices are installed approximately perpendicular to the backstop face and extend 4 to 6 feet out from the slope. The base of the ricochet catcher is typically 12 to 15 feet above the range floor, measured vertically from the ground surface at the target line. This prevents direct bullet impact into the catcher. Once major specification is that the ricochet catcher must be impenetrable to ricochets and should extend completely from side to side and connect the sidewalls. If overhead baffles are employed, the top of the backstop need only be 3 to 5 feet higher than the ricochet catcher. Specific construction details of the ricochet catcher will dictate the amount of material needed to ensure that the catcher is held securely in place.
2. Width. The width of the backstop should extend at least 5 feet beyond the intersection of the toe/bottom edge of the side berm and the outside targets/firing position. If the range has high side berms that closely match the height of the backstop then this requirement does not apply. Keep in mind that repair equipment needs adequate area to maneuver and work behind the target line. Therefore, this allowance may need to be greater.
3. Slope. The range side slope (side facing the shooter) must be as steep as possible, but not less than a 45-degree slope (a ration of 1-to-1). If a soil analysis determines that the soil will not support construction equipment, maintain the minimum required slope angle, or support vegetation, then it may be more economical to remove the poor soils and replace it with more suitable material. Special techniques may be required to stabilize the backstop.
In poor soil areas, gabions or rip-rap may be used on the offside of the backstop to stabilize materials.
Sandbags or automobile tires may be incorporated to maintain the bullet impact side of the slope. A major consideration if automobile tires are to be used is that they will present significant additional work time when the backstop is mined for lead. It is also necessary to fill the interior of the tires as they are put into place and before they are covered with clean fill. Steel-belted radial tires should not be used at all. There are many materials that can be used to stabilize the slope until vegetation can be established. Special netting material is especially useful to establish plants. Heavy vegetation such as large plants or trees should not be permitted on the top or range side of the backstops.
If columns of automobile tires are used as the core of the backstop, these columns must be supported by using utility poles inside each column with clean fill material added to the interior of each tire as it is put into place. Without filling the interior of each tire, the columns of tires will collapse, requiring the use of more tires. Not using utility poles or some other support for the column may cause the backstop itself to collapse. The use of wooden cribs for a backstop is labor intensive to maintain and is a less desirable construction method. They should be used only as a last resort.
Steel backstops are also an acceptable alternative when soils are inadequate. The primary drawback is the initial cost. However, if the projected quantity of shooting is substantial, the ease of recovering lead may quickly offset the initial cost. Basic maintenance costs also will be lower. Expect foundation work to be required to set and support this type of backstop. Because these backstops are constructed to the same specifications as indoor range backstops, an additional earthen barrier behind them may be needed.
Side berms and walls
These protective barriers may be constructed from earth, precast concrete panels, masonry walls, wooden cribs, wooden box-type structures filled with pea-gravel, crushed rocks, rubber tires filled with soil and/or poured concrete walls or panels. The specific type of structure will depend on available space, type of range being built and the relative initial cost. A major consideration that should be evaluated during the initial planning process is the long-term maintenance cost of the barrier being considered. Most times it is far more cost-effective to select the construction material that will provide the longest life while requiring the least maintenance.
Exposed tires present problems such as bullet bounce-back that must be addressed before they are used. If earthen side berms are selected, the construction methods will be the same as that used for the construction of the backstop. If concrete panels are selected, then some site work will be required to build their foundations. Concrete panels can be tipped into place or set into place using a crane. If masonry walls are selected, only skilled masons should be used. A substantial foundation will be required to prevent settling cracks or major damage caused by ground shifting. Experienced engineers and concrete companies should be employed to erect concrete structures, especially in earthquake-prone areas. If concrete walls (precast or poured-in-place panels) are selected, the specifications cited in the "NRA Range Manual" should be strictly adhered to.
Generally, earthmoving equipment will be used to construct the main backstops. If earthen side berms are the choice then retaining the equipment onsite to construct the side berms is often the most cost effective. Side berms generally vary in dimensions according to the specific need. However, if a side berm is to be used also as a backstop, as some shooting activities may require, then the side berm is considered to be part of the backstop and should conform to the same specifications as the backstop. In this situation, the overall height of the side berm, for at least that portion that is used as a backstop, should be the same as the backstop. It is important to remind all range owners/operators to carefully evaluate the shooting activities to be incorporated into their range facility and include them in the master plan.
Side berm, walls or barrier specifications are as follows:
1. Height. Generally, side berms, walls or barriers are suggested to be a minimum of 8 feet high, with 10 to 12 feet recommended. Side berms may be used on all ranges and on ranges that go a distance of 1,000 yards. Side berms, walls or barriers are used to allow shooters and range personnel to use adjacent ranges simultaneously. Another reminder: backstops, side berms, walls or barriers, in and of themselves do not eliminate the requirement for safety fan areas.
2. Length. Except as indicated above, side berms may be the same height and the full length of the range-from the backstop back to even with the most distant firing line.
3. Slope. The range side (the side facing the shooter) of the side berm should be as steep as is possible, but not less than 45 degrees or a ration of 1-to-1. These specifications are the same as those for the backstop.
Masonry walls are an alternative, but they should not be selected over precast or tip-up walls. The repair work for damaged masonry walls is often both labor intensive and expensive, whereas a precast panel can be removed and replaced with minimal effort and expense. Initially, an additional number of the precast panels can be purchased, which should significantly reduce the cost of such panels over having them cast again at a future date. Masonry walls using voided concrete block should be fully grouted and filled with concrete to add strength and impenetrability to the structure. Masonry walls should be reasonably protected against bullet strikes.
Wooden side baffles filled with selected materials may be used, but are not easily constructed, repaired or maintained. Obviously, the designs for side baffles will depend upon local site conditions and available materials. A point to be made about wooden box side baffles is that they must be tested before being built to ensure that they will stop the bullet for the caliber to be used. It is the rare exception that will require this type of structure to be more than 4 inches thick. A structure made to the thickness of 6 inches will stop all bullets from normally accepted sporting arms and individual infantry military small arms. If there are doubts, construct a test panel and conduct the appropriate tests before committing to any major construction expense. Test twice before building once. [See the "NRA Range Manual" for dimensions and drawings to construct a test panel.]
Precast concrete panels set at angles on each side of the range can prevent bullets, regardless of the angle fired laterally, from escaping the range. Generally, panels are manufactured onsite and tipped into place. These barriers withstand most bullet strikes without major damage. Stringent range laws can prevent shooters from inadvertently firing into the barriers. Shooters must demonstrate the appropriate skill necessary not to cause damage to range equipment.
The term safety baffle or overhead safety baffle defines a structure which is used to restrict fired bullets to smaller areas than would otherwise be possible without them. Safety baffles differ significantly from sound baffles, which are designed to absorb or redirect sound waves. Safety baffles are designed to be impenetrable. The basic concept is on the "blue sky gap." This means that baffles are erected so that the shooter, regardless of the shooting position used (or permitted) cannot see any sky downrange, either over the top of the backstop or to the sides of the range. Safety baffles may be overhead, on the ground, on top of the backstop, in the roof of the firing line cover, in the form of an elongated box, or as a completed enclosed tunnel. The principle behind the design is to equip a range with baffles so that if a fired bullet leaves the confines of the range proper, it will fall to earth within a smaller, more predictable area that is acceptable to protect people or property adjacent to the range.
If overhead safety baffles are not designed and installed properly, they can cause problems. They may redirect the fired bullet in the wrong direction, may not absorb the fired bullet as intended, or there may be gaps that will permit a bullet to escape the range. For any range on which overhead baffles are planned, carefully analyze the application beforehand and seek professional advice.
General specifications say that safety baffles must:
1. must be impenetrable for calibers to be used on the facility.
2. must be a minimum of 4-feet-tall for vertical baffles.
3. must be relatively maintenance-free.
4. if using concrete, must be designed to span lengths of up to 25 feet. Span length between columns is a product of design and overall range width.
The specific design and number of baffles that will be needed to protect a given area will be dictated by the amount of free space around a particular range facility.
Vertical overhead baffles are a standard 4 feet high with the bottom edge set 6.5 to 7 feet above the horizontal surface of the range. The width dimensions are the entire width of the range connecting to both side berms or walls.
For baffles constructed from plywood and filled with high-density material, use 3/4-inch marine plywood on the firing line side, 5/8-inch on the downrange side, and built into a box with an inside dimension equal to the width of a standard 2x4-inch piece of lumber. Again, fill materials must be tested before use.
Baffles may be built by laminating wood and steel or by a special concrete panel design. Laminating baffles using plywood and 10-gauge steel requires a lamination thickness of three sheets of plywood with two sheets of steel sandwiched between; nominally the lamination thickness is 2.5 inches.
Slanted overhead baffles are 9 feet wide and set at a 25-degree angle to the ground as measured from the front edge (the firing line edge being higher than the rear edge). The slanted overhead baffles are a minimum of 3-inches-thick, prestressed concrete slabs, and must pass 3,000-pound, 28-day, compressive strength test.
It also is important to keep in mind that it may be necessary to incorporate a series of ground baffles within the overall design. Ground baffles reduce the ground surface area that a bullet might strike. When properly designed and installed, ground baffles do reduce ricochets, but do not totally eliminate them. When the downrange area is viewed from the firing line, the shooter will see overhead baffles, ground baffles and the target and backstop immediately behind the target. No blue sky will be visible, nor will any of the horizontal ground surfaces of the range.
Generally, ground baffles should always be used with overhead baffles and must be:
2. minimum height to correspond with the placement and horizontal surface area to be masked. Multiple ground baffles may be required for a 50- or 100-yard range. The goal is to mask the range floor beyond the first baffle.
3. relatively maintenance free. Ground baffles are designed to meet the needs of a particular facility.
The dimensions for ground baffles are a minimum of 3 inches thick if made of plywood and should be backed up by an earthen berm. If a wooden top cap is used, particular attention should be paid to the direction of the wood grain. It should always curve downward.
Materials for ground baffles may be concrete (firing line surface should be 2-by- wood stock covered to prevent bullets from being redirected toward the firing line, pressure-treated wood, steel (firing line surface should be 2-by- wood stock covered to prevent bullets from being redirected toward the firing line), earth or a combination.
When developing the overall safety plan, when overhead and ground baffles are to be incorporated, the level of protection will be dictated by the free space downrange. For example, will the downrange free space permit a 45-degree ricochet escape, or must the angle be increased to 60 degrees or higher? The maximum protection is to install the overhead baffles to protect against a 90-degree ricochet. That is tantamount to an indoor range level of protection. The amount of free space available outside the range barriers will dictate the level of ricochet protection required.
The bottom line is to develop a shooting range in harmony with adjacent properties and where safety is provided to prevent adjacent properties from experiencing any encroachment. All neighbors must be safe from injury. The overall responsibility of the range owner/operator is to stop fired bullets before they exit the property line.
Safety first Aaalways. smiley-10-sign
One of the things I really liked about Jeff Cooper's Gunsite was that he used corrugated viaduct lined with insulation to control noise.
A benefit of it was that it kept fire on the target area.
A target pit angled down into level ground, with a timber backstop and loose soil piled in front makes a good backstop for areas without natural backstops. The spoil from the pit is heaped up behind the pit to provide ricochet protection.
Add one of Cooper's viaducts and you have a good setup for areas where overshot can be a hazard.
At regular intervals the soil in the pit can be screened, the shot recovered and remelted.
An unusual but good notion is an underground range. It consists of target and shooting boxes lined with timber, and a 50 foot trench with 24 inch viaduct connecting them. This can be constructed in areas where shooting would otherwise be impossible. The pits are accessible by hatches and the entire structure is invisible.
A safety feature is a timber box/soil backstop situated behind and above the target box, to catch any misfires that penetrate the upper viaduct and the one foot of soil covering it.
Place a small shed over the shooting box and it becomes a lot more weatherly as well. The soil behind the target box can be screened and the shot recovered.
Such ranges can be built in suburban areas and used without the neighbors even being aware of them.
It is somewhat of an engineering task, but a relatively simple and inexpensive one.
Sounds like some good ideas. I was wondering though about the underground one, wouldn't it be kind of unhealthy with the fumes off the powder and lead.
|QUOTE (Almtnman @ Jan 2 2007, 02:40 PM)|
| Sounds like some good ideas. I was wondering though about the underground one, wouldn't it be kind of unhealthy with the fumes off the powder and lead. |
Oh yeah - you definitely have to include a baffled vent fan.
The best would be an out-fan in the target pit. However with a shed over the shooting box you can install a blowfan that forces the air down the duct and out through a vent in the target box.
I'm kinda sweet on these because like icefishing sheds you can add all kinds of fun geegaws.
Though I shoot out in the woods; I have many times considered building something to be safe.
I might just have to get serious about this one.