The 7mm High Velocity:
In 1952 after the NATO trails it became clear that the United States would never adopt the .280/30 Enfield round.The reason for this refusal was the lack of power compared with the .30-06 round (the service round of the U.S. army at that time, used as a reference) and the American experimental T65 cartridge.
In an attempt to increase the performance of the .280 Enfield cartridge the United Kingdom developed the 7mm HV. (High Velocity)
The case of this round was increased to 49mm, and had the same neck-angle / taper as the .280/30. because of the enlarged capacity of the case, it could be filled with more propellent.
The Muzzle Velocity of the 7mm HV was 2760 (fps). (for the .280/30 is the M.V. 2415 (fps)
the 7mm HV was produced with several loadings;
Ball, plane with GM envelope
Ball, plane with CN envelope
Ball, with yellow bullet tip (type B)
Ball, With brown bullet tip (type BC)
Grenade, rosecrimped case
Drill, inert ball round
7mm HV, (.280/30 for comparison), sectioned version and headstamp.