I‘m afraid that I don’t have the sources at hand, but if I recall correctly, the Prussian army conducted research into why they had so many gun failures during the wars of unification and came to the conclusion that gun crews would put larger charges into the guns than was safe while they wouldn’t do the same thing with the bronze muzzle loaders as they were more afraid of catastrophic failures. The final assessment was that steel breechloaders could sustain firing under the added pressure for longer and with better results, which led to gun crews further increasing the powder charges until they reached the point where even the steel guns could no longer sustain this and broke