The U.S. used 75mm, 90mm, and 105mm versions in the Korean War. These lightweight artillery pieces ejected propellant gases from the rear to counteract the weapon's recoil. Of course, you don't want to stand behind them when it is fired. Apparently, on more than one occasion ... when GIs recovered recoilless rifles that had been commandeered by the enemy in battle, they found dead North Koreans/Chinese lying directly behind these weapons. Oh well ... if you don't have the manual ... I suppose someone has got to take one for the team, eh?
The essential American soul is hard, isolate, stoic, and a killer. It has never yet melted. ~ D.H. Lawrence