From Wilfrid Ward's piece "The Action That Served Two Armies" (Gun Digest 1994 Annual, there is this interesting snippet about the P / 13, the prototype that the P 14 / M 1917 rifles were made from: " . . . in late 1915 some of the original thousand P 13s, by then returned to store, were converted to 470 caliber for use against snipers' plates . . .similar use had been made of heavy-caliber big game rifles . . ."

I am curious about whether this was the 470 Nitroexpress, or some rimless 470 experimental round? Ward goes on to say that 303 armor-piercing ammunition put an end to this experiment.

Thanks for any information on this historical question, in advance. It would be interesting to know what the Brits experimented with in military rifles while they were building some of the world's finest sporting double rifles and single shots.