This is a replica of the 30 Cal. 1000 yard Danger Space cartridge. It was an experimental round that dates from April 1910 at Frankford Arsenal and the idea was to develop a round that would give a continuous ‘danger space’ of 1 000 yards, meaning that the flight of the bullet must not rise above the height of a man standing on even ground. This might have been the first of these experiments and the 28 Cal round is probably a necked down version of this.