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2. Boyle, P., Humphrey, A., Courtney, M.: Quantifying friction effects of molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, and lubalox as bullet coatings. US Air Force Academy Report ADA568594 (2012)
3. US Patent US20140230683 A1: Reduced friction expanding bullet with improved core retention feature and method of manufacturing the bullet (2014)
4. Summer, P., Courtney, M.: Friction effects of lead-based and lead-free primers in 5.56 mm NATO” US Air Force Academy Report ADA594429 (2014)
5. Voxnews: Army testing new ‘green’ bullets. http://www.foxnews.com/tech/2011/05/04/army-demonstrate-new-green-ammo-maryland/ Last call on 22 May 2015