Although the British had adopted .380 as their standard revolver cartridge in the interwar period, there were still many older revolvers in the heavier .455 cartridge in service and so manufacture of the ammunition continued into the Second World War. Today we are looking at an inert round dating from 1942. It has a brass case with a prominent extraction rim at the base:

The lead round is held in the case by a series of crimps at the top of the case:

This round is a Mk VIz and was manufactured by Kynoch in 1942:

British Military Small Arms offers the following details about the Mk VIz round:

With war drawing close in the late 1930s, attention was once drawn to the legality of the lead bulleted .455 inch Ball Mark II. The Germans had formally objected to it in WWI and so it was decided to introduce a jacketed version of the bullet.

“Cartridge S.A. Ball Revolver Mark VI” was approved to design DD/L/9513 in September 1939 and shown in LoC Paragraph B.3313 dated March 1940. The nitrocellulose loaded version was approved as “Cartridge S.A. Ball Revolver Mark VIz” in April 1941 to design DD/L/9613 and shown in LoC Paragraph B.5974 dated April 1942. Both were superseded by design DD/SAA/149 in January 1945.

The case was as for the Mark II but did not have the bullet seating cannelure. The headstamp included the numeral “VI” or “VIZ” depending on the propellant, and the primer had a purple annulus.

The bullet had the same profile as the Mark II and had a lead core with a cupro-nickel or gilding metal envelope. It weighed 265 grains and was secured in the case by three neck indents.

It is interesting to compare the three most common rounds for British side arms in World War II, l to r .455, .380 and 9mm: