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Baffles, Berms and Backstops
By David Luke,
Range Technical Team Advisor
(This article is reprinted from the Third National Shooting Range Symposium, 1996 with permission from International Association of Fish and Wildlife Agencies, Wildlife Management Institute and U.S. Fish and Wildlife Service.)
During this session, I will talk about points that fall into the "lessons learned" category of shooting range design that, while listed in the "NRA Range Manual," are not always given the appropriate level of importance by the prospective range owner/operator. The detailed and specific minimum construction specifications are in the "NRA Range Manual." [To obtain a copy of the "NRA Range Manual," contact the NRA at 11250 Waples Mill Road, Fairfax, VA 22030, (800) 336-7402. Refer to "NRA Range Manual," Order 14840.]
Before we get into specific discussions about main topics of this session, it is important to touch on several points that will help keep this session in perspective.
1. The safety plan. This plan focuses on how, what, when, why, and whom. This document is developed during the planning, design and construction phases of a range complex. The safety plan is a living document and must be continually reviewed and updated. If this plan is left to the end, the facility owner/operator may find some undesirable surprises as he prepares to open for business. The safety plan is an important portion of the master plan.
2. The 4-Es. The 4-Es must be used at every step of developing a shooting range. The 4-Es are: evaluate, engineer, educate and enforcement.
A. Evaluate the needs of the prospective user and identify the specific shooting activities to be conducted on the facility. Evaluate how many shooting activities will be conducted on the same piece of ground, but not necessarily simultaneously. Setting times and schedules for various activities to ensure there are no conflicts in range usage is an important consideration. While there are a few differing shooting activities that would be compatible and lend themselves to simultaneous range use, most are not.
B. Engineer each range to accommodate the specific activities which you have evaluated and are to be conducted on the same piece of ground/range. Intimate knowledge of each activity and a rule book specifying the detailed requirements (if applicable) of each activity is essential. Each activity's requirements will have to be considered in detail to ensure no conflicts in firing line design, target line location, target placement and target set up, etc. Time efficiency is also an important consideration when switching from one activity to another. While it is possible to conduct multiple activities on the same range, it will require deliberate thought and careful consideration to ensure possible conflicts are insignificant and kept to a minimum. Once the design criteria have been established, it will be important for the owner/operator to truly understand that there will be very little room for change in use without returning to the evaluation phase with a view toward additional engineering to retrofit the range to accommodate the new activity.
C. Educate the operators and those who will be using the facility (users) in the specific actions that are acceptable. Firearms, firearm calibers, positions that can be used (standing, sitting/kneeling, prone), types of firing (slow fire only, rapid fire, etc.) are but a few topics that should be taken into consideration from inception as to how the range will or may be used. Briefings on the etiquette of firearms safety, how and when to approach the firing line, how and when to change targets, commands that will be used-and their meanings, range officer authority, etc. Careful consideration in this area will reasonably ensure that the facility will never be used outside of its design criteria and thereby cause problems for the owner/operator.
D. Enforcement is the final phase of the 4-Es and ultimately is the glue that will hold all these considerations together into one cohesive package. Enforcement solidifies the safety plan. The owner/operator must consider the specific methods and actions that will be employed to ensure the range is always used within the design criteria. Ultimately, it will be the responsibility of the owner/operator to determine the method to be used, assuring adherence to the rules and regulations established.
3. Purpose of backstops, berms and baffles. Erecting berms, backstops or baffles may be an optional construction consideration for range owners/operators who control 1.5 miles downrange for pistol or 3.5 miles downrange for highpowered rifle, with appropriate left and right ricochet safety zones. I believe all of us would readily agree, that this scenario is the exception rather than the rule. Therefore, the primary purpose for the construction of backstops, berms and baffles is to protect against the injury of people, the damage of property or both. A secondary benefit is to permit the systematic recovery of fired lead projectiles-definitely a recoverable and recyclable resource that can contribute significantly to the positive cash flow of a range facility.
4. Projectile/bullet containment. It is the ultimate responsibility of the range owners/operators to ensure that the projectiles fired on their range are contained within property boundaries. While it is entirely possible for an existing range facility to be grandfathered against noise complaints, it is unlikely any governmental body would make the same concession concerning safety. Therefore, it is paramount that shooting range owners/operators continually evaluate the shooting activities permitted and the requirements necessary to ensure those activities can be conducted with projectile/bullet containment as a primary goal. The level of requirement necessary for the projectile/bullet containment on a shooting range facility will dictate the extent of the backstops, berms and baffle construction.
5. Shooting range safety fan. It is important to frequently remember that while specific range safety fans are specified in the "NRA Range Manual," these safety fans presume a free and open range. As more and more controls and barriers are added to the design (both administrative and physical), the required range safety fan becomes smaller until eventually the range safety fan equals the exterior edges of the barriers. This point is not specifically made in the "NRA Range Manual" and also is not a logical conclusion by those not familiar with range design and construction. These same folks seize on a specification and fail to understand that by adding controls or barriers, the range safety fan specifications are changed, usually significantly reduced. Backstops and side berms do not remove the requirement to include a safety fan.
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.