I am kicking around an idea, but I wouldn’t be surprised if it hasn’t already been tried before. It would be for guns that removing the barrel is not a good option. It would involve a flexible tube with a spray nozzle on the end and using a low pressure water supply like maybe a 1 gal pump up weed sprayer. I envision using a cradle to hold the gun muzzle down, lock removed, torch hole/nipple plugged. The tube would have to be small diameter, and the spray head probably fabricated to spray out the end of the nozzle and laterally out the sides of the nozzle at the same time. Has anyone tried something similar? What are your thoughts pro and con?