if you mean do they take cartridges - no they don't. The law changed several years ago and cartridge pistols are now Section 5 firearms and only legally available to the very select few.
These guns are loaded by pouring a measured charge of powder into each chamber from the front (hence 'muzzle loading'), putting in some packing material (either a thick fibre wad or semolina for example), ramming a ball onto the top, placing a percussion cap on a nipple on the rear of the chamber, cocking the gun and pulling the trigger. Big cloud of smoke, big bang, hole in the target (hopefully!)