16 Shots at hand via 16th Century firepower
From the National Firearms Museum:
Created in Germany around 1580, this wheellock rifle has a very unusual design. The gun is capable of firing 16 shots that have been superposed in the barrel. The forward lock fires the first 10 shots and the rear lock fires the last six shots. If either of those locks fail, there’s a backup matchlock at the rear that can set off all of the charges if necessary.
This is the only known example in existence and has been part of famous collections over the years. It was even featured in the 1950s gun book, “Firearms Curiosa,” by Lewis Winant.