When I built my duckfoot kit gun, I took it to the club range, and tried it out. 15 grains of FFg in three barrels was a handful to hang onto when the gun fired. It HURT! I have big hands, and these guns don't have large grips. I backed the loads off to 10 grains of FFFg ( .31 caliber ball). We tried shooting it a 3 yards, and 5 yards, and at 5 yards,( 15 feet), the hits were spread far enough apart that if I went back further I might miss two men standing shoulder to shoulder with the center guy I was pointing the center barrel at.
These were designed to defend ship's captains, in the narrow confines of the stairs, and hallways on board ships. Because the angle of the barrels is fixed, and the caliber is so small, there is no point in loading the barrels with shot. Its a shoot and drop, and grab another pistol to fire again kind of thing. At the short range these guns are designed to be used, they can hurt an enemy very well, and disable him enough to step forward and kill him with a sword thrust, before his accomplices behind him can get past his falling body to reach you with their swords. Oh, the smoke that three barrels produce is also something to consider when fighting in a closed area. I don't know how any one could see anything through that cloud of smoke for at least 10 seconds, and thats a long time to hold up an attack. I can't imagine the panic that would set in when seeing the flash of not one, but three barrels all at one time coming towards you.