Why Welin breech blocks were not adopted earlier

What prevented the Welin breech block from being invented in the 1860s or 1870s?

Metallurgy, understanding of pressure, manufacturing technique, and someone conceiving the design were the principal constraints.

An earlier Welin breech block required both the design idea and an industry able to build it. A stepped interrupted-screw breech had to withstand demanding pressures and be manufactured reliably. Some relevant techniques already existed by the 1870s, but metallurgy and pressure knowledge still limited what could be produced safely. The concept therefore cannot be moved backward in time by assuming that its shape alone was obvious.