Quantifying Friction Effects of Molybdenum Disulfide, Tungsten Disulfide, Hexagonal Boron Nitride, and Lubalox as Bullet Coating.

摘要

Molybdenum disulfide (MS2), tungsten disulfide (WS2), hexagonal boron nitride (HBN), and Lubalox are common bullet coatings that purportedly reduce friction between the bullet and rifle barrel. Three different bullets, one a solid copper design, and two jacketed lead bullet designs, were tested in the 5.56 mm NATO rifle cartridge. After coating, these bullets were test fired through a chronograph with powder charges ranging from 0.52 grams to 0.91 grams. The energies of these bullets along with a control group of uncoated bullets were plotted against the powder charges. The work of friction for each combination was then determined as the vertical intercept obtained by least squares regression to a line. The different coating and bullet combinations produced changes in friction ranging from reductions in friction of 15% to increases in friction of 19%. Given the time and expense of coating bullets, the reduction in friction is not cost effective for most applications.