BTW, .577/.450 is a .45" calibe. It was based on the old .577" Snider casing, stretched out to 2.34" and necked to a .45. Also known as the "Short Chamber Boxer" round to differentiate from a full-length .45 Boxer-type rolled cartridge which could hold 85 grains of RFG #2 powder. There were NO military .577" Martinis made, although a few were turned out by the Trade for hunting Elephant and other bignasties; they are very rare.
With the original barrels, they are Martini-HENRYS and have HENRY ratchet rifling.
Changed over to a .303, they are Martini-METFORDS if using the old METFORD segmental rifling, Martini-ENFIELDS if using the ENFIELD 5-groove rifling with equal lands and grooves. The presence or absence of an "E" on the Knox-form tells you which you have.
The Martini ACTION is one of the strongest ever made. It also has the quickest LOCK TIME of anything ever built, which is why it is still in production today.
The .303" barrels were all proofed for a Service pressure of 18.5 Imperial Long Tons per square inch (41,440 psi), precisely the same as the Lee-Enfield and Pattern 14 bolt-actions.
.