SRM 2460/2461 standard bullets and casings project

Abstract

The National Institute of Standards and Technology Standard Reference Material (SRM) 2460/2461 standard bullets and casings project will provide support to firearms examiners and to the National Integrated Ballistics Information Network (NIBIN) in the United States. The SRM bullet is designed as both a virtual and a physical bullet profile signature standard. The virtual standard is a set of six digitized bullet profile signatures originally traced from six master bullets fired at the Bureau of Alcohol, Tobacco and Firearms (ATF) and the Federal Bureau of Investigation (FBI). By using the virtual signature standard to control the tool path on a numerically controlled diamond turning machine, 40 SRM bullets were produced. A profile signature measurement system was established for the SRM bullets. The profile signature differences are quantified by the maximum of the cross correlation function and by the signature difference between pairs of compared profile signatures measured on different SRM bullets. Initial measurement results showed high reproducibility for both the measurement system and production process of the SRM bullets. A traceability scheme has been proposed to establish the measurement traceability for nationwide bullet signature measurements to NIST, ATF and FBI. Prototype SRM casings have also been developed.

Three Steps towards Metrological Traceability for Ballistics Signature Measurements

“…A SRM 2460 standard bullet is shown in Fig.1, left, which is designed as both a virtual and a physical ballistics signature standard [1]. The virtual standard is a set of digitized bullet profile signatures that provides the profiles for machining the bullet signatures on the physical standards, the SRM bullets.…”

“…Two property values, a NIST proposed parameter called the topography difference D s and the cross correlation function maximum CCF max , are calculated for both 2D and 3D ballistics signature measurements [1,2]. CCF max is the maximum value of the cross correlation function (CCF), which occurs when the two correlated surface topographies, the measured topography Z (B) and the reference topography Z (A) , are registered at their maximum correlation position.…”

“…These are replicated from an ATF master casing using the electro-forming technique [1]. We intend to fabricate 256 replica casings with essentially the same topography.…”

“…The virtual standard also provides reference profiles for the measurements of the machined bullet signatures on the SRM bullets. The virtual standard was originally obtained from topographic profiles traced by a stylus instrument on master bullets fired at the ATF and the Federal Bureau of Investigation (FBI) under standardized shooting procedures [1]. The virtual standard was stored in a computer and used for control of the tool path of a numerically controlled (NC) diamond turning machine at the NIST Instrument Shop to machine the bullet signatures on the SRM bullets [1].…”

“…IST) in collaboration with the Bureau of Alcohol, obacco, Firearms and Explosives (ATF) has developed the Standard Reference Material (SRM) bullets and casings [1,2]. NIST and ATF are proposing to establish a National Ballistics Measurement Traceability and Quality System for ballistics signature measurements and correlations using these materials [3].…”