The HK series were initially designed as 9mm and then adapted to the .40 cartridge.
That's news to me. Are you sure? Positively sure, not biased of your sig?
In 96 the USP became the German Army pistol in 9mm. Later in 96 the UPS compact was introduced in 9mm .40 and .45.
The original was the Glock 22 followed closely by the Smith & Wesson SW40F.