Smokeless powder and metallic cartridges were both watershed changes for firearms. metallic cartridges protected the powder and made re-loading vastly, vastly faster. Like I think they had problems with logistics for the early metallic cartridge rifles because troops were shooting so fast they were running out of ammo.

Smokeless powder, too, was much more powerful and not producing huge clouds of smoke was a great tactical advantage. The only problem would be that you need high quality metallurgy to make steel that can handle the pressure of the explosion.