>>938436031
you need a rifled barrel to use a bullet shape effectively without it just tumbling around. and with black powder the barrels foul quickly, especially rifled barrels. when fouled there is too much crude in the barrel to ram the muzzle loaded round down it. so you`d need to clean it so constantly that it reduces your firing rate making it not as worth it.

however the minie rifle solved this issue to some extent in 1849. the innovation here being projectiles smaller than the barrel allowing it to be shoved down the barrel even while fouled. and lubed with grease in the grooves, also the bottom of the round deformed during firing to create a tight enough seal. pic related.

later breech loading rifles became widespread and replaced the minie rifle within 20 years after the minies release. so you didn`t have to shove the round down the barrel like with previous muzzleloaders made pointy projectiles even more practical. and then integrated cartridges and smokeless powders were also a big help, much less fouling.