I believe DD is our resident expert when it comes to Martini's.
He was not a fan of the adaptor cartridge for this old rifle due to the way the chamber is cut, the adaptors stuck after firing?
Perhaps it is just luck as old mate had no issues in the link above?
I have a BSA MkIII built in 1887 that can still do her job, yes she shoots very high at close range (like most do), its great fun obliterating the range with BP smoke & pissing .223 & 6.5Creedmore owners off - all in the name of mosquito control