The Jones Screw-Grip was patented in 1859. Fleming says the .577 Snider appeared in 1866, and I imagine that these early cartridges were inside primed. What I'm not sure about is which rules of proof first required rifles to be stamped with the bore size in decimals of an inch. I know that it was required by the 1887 rules, but I think it may have been under the 1875 rules. Anybody know?

At any rate, it looks like not earlier than 1866 and not later than 1887 for sure. By the 1880s, the wedge fore-end retainer had been pretty much displaced by the various modern fore-end fasteners that were patented in the 1860s and early 1870s. My guess is early 1870s.
----------------------------------------------------------