Generally speaking, when an improvement is made in firearms, older guns are either (1.) updated or (2.) given a dignified retirement You've got to love the Brits though — it seems nothing ever gets discarded on the sceptered isle. Why shoot those new-fangled self-contained cartridges in your new Purdey or Holland and Holland, when you can convert it to a muzzleloader — just like the old one that you gave to the gamekeeper's son last week, to help keep down the vermin on the estate.
William Evans offered "Solid Steel Converters" that one could stick in his breechloader and convert it back into a front-stuffer, by simply loading it with loose powder, wads and shot and then putting a percussion cap on the nipple that could be fired by the striker. Advertised as "most invaluable in remote parts where paper cases are not procurable," these sold for the not-unsubstantial price of 8s. 6d. a pair (the average wage of a British workman in 1900 was about 18s.), and don't seem to have had much vogue, despite the 19th century English habit of traipsing all over the globe. Just some other demmed-thing for the mem-sahib to pack, I suppose.