Hi All,
A few Martinis may have been chambered for the .577 Snider cartridge how ever most were chambered for the .450 Short chamber which later became know as the 577/450. The original .450 cartridge was long and thin and prooved fragile in service with it's rolled brass construction. Remebr drawing brass was not developed back then.
Velocity of the .450" 480 grain lead bullet was about 1350 fps and it hit like a tons of bricks. Penetrated well too. Martinis went through several marks oen enve had an extended lever due to extraction problems caused by the rolled brass cases in the tropics. Later drawn brass cases solved this problem. The Martini was certainly faster to reload and fire than the Trapdoor Springfield and pulling the lever down not only extracted and ejected the case but cocked the action as well. Put a new shell iand close the lever raise to aim anf fire. No hammers to muck with
Now out in the Gulf there are a lot of fakes as well as lot's of originals you have to be careful. Some of the originals are in bad shape and some messed with and there are some in 303 as well. 303 Martinis were popular in South Africa with the Boers and Oman in the Gulf used them as well. The British army used several marks of 303 Martinis those with Metford rifling are Martini Metfords (MM) and those with the later Enfield form are Martini Enfields (ME) and they all came in long and short versions. Sevaral carbine versions were adopted and issued.
Of course Egypt also adopted the Martini and those marked Citidel are Egyptian so the choice is varied and confusing to those new to them. Luckily the home built ones are more often than not marked incorrectly but to knwo this you need to be familar with the correct marking and there are books devoted to just this.
The trap doors you speak of, now does the breech block swing sideways? if so they are probably Sniders and most likely in .577" this was the stop gap breechloader a conversion of the .577 muskets along the same lines as the US trapdoor Springfields. Again it's buyer beware they might be originals they might be fake and both types may or may not be safe!