The 50 mm Krupp Mountain Gun is such a gun designed in the mid 1890s. The French 75 is such a gun and would make a fine gun in 1/2 scale from 1897. There are quite a few Spanish, French, British and American deck guns in this class and most are known as QF guns, "Quick Fire". They date from the mid 1880s to late 1890s. We would not build any cannon that takes a complete cartridge which includes primer, powder, case and bullet in one complete package without sending an inquiry letter to BATFE and getting an official OK to proceed. Don't assume anything here; get an Official OK first! BTW we don't even discuss what may or may not be legal here on this board; it's in the rules. Good luck; we hope you choose a good one, get the OK and then build it!!
Tracy and Mike