Compared to the advances that permeate so many other technological fields, firearms have been a very mature technology for a very long time.
The only technological advances in man-portable firearms since the 1930s have been in materials and construction methods. I am unaware of any completely new operating mechanism after roller-locking recoil. Certainly the gas-operated, rotating-bolt, box-magazine-fed rifles which arm our troops would be instantly identifiable to John Browning in his 1890s Utah workshop, although the machined aluminum forgings and plastic furniture might seem novel to him.
A SIG P-226 would only be “exotic” to Le Maitre in its use of stampings in place of machined forgings. Other than that, it’s a short-recoil tilting-barrel box-magazine-fed self-loader, still shooting a cartridge developed for the Imperial German Army in the first decade of the last century. (Just think about cartridges: Of the major martial firearm chamberings, only 5.45, 5.56, 7.62×51, and .40S&W were developed after 1945, while .50 BMG predates the last World War and 9×19, .45, and 7.62×54 predates the one before that.)