False muzzle became popular after the Civil War( lr The War Between the States) , although some existed earlier. Target shooting with bench guns became the rage with veterans of the Civil War,and there was much development occurring as cartridge breechloaders were overtaking muzzle loaders in target shooting circles. False muzzles were used well into the cartridge era by men who understood that keeping the base of the bullet flat, and square to the bore was best achieved by seating the bullet down the muzzle, so that the cuts in the bullet made by the rifling would be pushed forward past the forward driving band and onto the Ogive of the bullet, and not back to become burrs hanging off the base of the bullet, to break off unevenly and thereby cause the bullet to fishtail going down range. Hayy Pope, the famous barrel maker, popularized using false muzzles with breech loading target guns. He later made bullet seaters for single shot breechloaders, that allowed the bullet to be carefully seated in the rifling in front of the chamber, and then a loaded cartridge put into the chamber behind the bullet, with only a card wad sitting in the top of the casing to protect the base of the bullet. This card prevented gases from cutting around the bullets, and protected the base of the bullet until the bullet left the muzzle of the gun. Harry always believed that you got better accuracy with lead bullets if they were seated down the muzzle, tho'.
False muzzles are always made from a section of the barrel cut off. The FM is given a tapered bore, to help align the the bullet in the rifling, and to make it drive straight, without canting, down the barrel. Because the width of the saw blade used to cut the false muzzle from the rest of the barrel caused a slight misalignment of the rifling from the muzzle to the false muzzle, care was taken in drilling the pinholes through the false muzzle into the muzzle of the gun, so that the two could be aligned, to make sure that the rifling married exactly at the junction. Sometimes a lead slug was run down the barrel and left partway in both the barrel and false muzzle during this operation to insure that alignment. You can still see these fascinating pieces of history being used on the Slug Gun Range at Friendship, during the nationals. There are slug gun matches fired around the country, if you can't make Friendship. Call the NMLRA for information on the closest shoot, if you are interested. George Mitchell brought his 100 lb, .69 cal. slug gun to a meeting of our gunclub, where most of the shooters had never fired a muzzle loader in their lives. When he showed them how a false muzzle is actually used in loading a bullet into the barrel, you could have heard a pin drop, and stolen all their wallets! That is how fascinated the shooters were in what he was showing them. I can't believe that anyone on this site would be less interested. Th eslug gun boys do all the Research And Development in the Black Powder science these day. If you have a question about loads, lead alloys, patches, primers, cleaning, etc. you can almost always get the most accurate and useful answers talking to these men and women. George had a 500 yd. target with ten shots that measure 5.26 inches across for the group, fired with his .69 cal. gun. That barrel was 8 inches across the flats, and the entire gun weighed that 100 lbs. Barrel was 42 or 48 inches long. I have forgotten that detail. He had his custom shooting bench made just for that rifle, as is the practice among slug gun shooters. He fired 350 grains of FFFg powder behind a 2 piece slug wrapped in a paper patch, made from onion skin paper, and lubed with sperm whale oil. Velocity, measured 20 feet in front of the muzzle was 1050 fps. I guarantee you that those 10 shots fired at the 500 yd. target would have all stayed under 1 inch at 100 yds. 10shots in one small hole. That is what false muzzles allow you to do with BP rifles.