Discussion
One of the most important factors in the success rate of the IBIS correlator is the size of the database used for correlations, as the success rate has been shown to decrease as database size increases(1).
It is important to use a database of sufficient size, however, to properly evaluate the two systems.
Before a bullet can be compared by either IBIS or BulletTRAX-3D, it must first be determined to
have the same class characteristics.
These are design features that are chosen by the manufacturer and include caliber, number, width
of lands and grooves, and direction of twist.
All 475 bullets in the database used in this study consisted of identical class characteristics,
with the exception of LEA and groove engraved area (GEA) widths, which vary.
LEA widths of the database bullets ranged from 0.057 to 0.095 inches and the Para-Ordnance bullets had a LEA width range of 0.070 to 0.079 inches.
However, IBIS has a LEA width tolerance of +⁄)10%.
That means that it will compare bullets that have at least one LEA width either 10% narrower than the narrowest LEA or 10% wider than the widest LEA of the reference bullet in question. When taking this tolerance into account, there were only two bullets in the database that were completely excluded (no LEAs from the bullet fell within the 10% tolerance) from comparison based on LEA width, leaving 473 bullets suitable for comparison.
It should be noted that IBIS does not make exclusions based on GEA width and BulletTRAX-3D does not make exclusions based on either LEA or GEA width, but instead exclusions are based on topography.
The database used in this study contained a larger number of 45 caliber, six land and groove, lefthand twist bullets than are currently in the database at the CFS in an effort to provide a realistic challenge in the evaluation of the two systems.