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 MIL-HDBK-1027/3B
b) Venetian Blind Type. Where space is limited, the commercially
available, "venetian blind" type bullet trap may be used. If necessary to
prevent backsplatter and reduce lead dust flow, provide commercially available
target backing curtains of rubber or cloth, loose hung in front of the bullet
trap. Types and caliber of ammunition which can be contained by backing
curtains must be in accordance with recommendations of curtain manufacturer.
Curtains also provide sound reduction of noises emanating from the bullet trap
area.
2.1.5.1
Bullet Trap Steel Specifications. Different types of steel for use
in bullet traps have been mentioned in various reports and manuals. The type
of steel used in existing facilities in present backstops may be unknown. The
use of "regular quality" steel plate or carbon steel plate conforming to
American Society for Testing and Materials (ASTM) A36, Standard Specification
for Structural Steel, is not recommended for backstops. Where this steel has
been used, rapid deterioration (pitting with resultant backsplatter) has been
experienced even with the use of only .22 cal. rimfire ammunition. Similarly,
High-Strength Low-Alloy (HSIA) steels conforming to ASTM A242/A242M, Standard
Specification for High Strength Low-Alloy Structural Steel, A441/A441M
Specification for High Strength Low-Alloy Structural Magnesium Vanadium Steel,
and A572/A572M, Standard Specification for High-Strength Low-Alloy Columbium-
Vanadium Steels of Structural Quality do not have sufficient pitting
resistance to provide an adequate backstop. Steel specifications shall
conform to the following:
a) "Armor plate" steel conforming to MIL-S-16216 J(1) performs
satisfactorily but is not readily available from ordinary commercial sources.
Manufacturers of commercial backstops and bullet traps use an alloy steel
known as ARMOR 46 (refer to MIL-A-12560 G(1) Armor Plate, Steel, Wrought,
Homogeneous (For Use in Combat-Vehicles and Ammunition Testing)), that has
been heat-treated to a range of 340 to 440 Brinell Hardness Number (HN).
b) Abrasion-resistant carbon steel rated at 225-285/BHN is suitable
for backstops where firing is limited to .22 cal. rimfire ammunition. This
steel requires special welding techniques, and might not be readily available
in some areas.
c) Possibly the best steel for .22 cal. rimfire ammunition (not
magnums) conforms to ASTM A514/A514M, Specification for High-Yield-Strength
Quenched and Tempered Alloy Steel Plate. Suitable for Welding. Surface
hardness will vary from 235 BHN to 293 BHN. This steel is readily available
under various trade names from major steel manufacturers and has good
weldability, when low hydrogen conditions are maintained, and recommended
electrodes are kept dry. The "Stringer-bead technique" is preferred with heat
input limited.
d) For center fire pistols the steel should be abrasion resistant
conforming to BHN 320, BHN 360, and BHN 400, with such trade names as Joalloy
AR-320 (Jones & Laughlin Steel Co.), X-A-R-15 (LTV), T-1 type A321 (USX), SS-
AR-321 (ARMCO) and RQ-32lA (Bethlehem steel). Steels which have higher
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