The New 40: HK’s M320 Grenade Launcher by Joe Katzman | Feb 2, 2014 | Contracts - Awards, Grenades, Guns - 20-59 mm direct, New Systems Tech, Other Corporation, USAHK M320 on M4(click to view full) Sometimes, 5.56mm just isn’t going to get the job done – and neither will any other standard rifle caliber. Shoulder fired rockets are heavy, which limits carrying capacity, and can’t fill all needs with their...