I recently re-watched the Forgotten Weapons video on the Pederson Device and it got me thinking. What if the 1919 Spring offensive had occurred and the Pederson, Thompson and M1918 BAR were pressed into extensive front-line combat, and how would that change small arms development.

My main focus was the Pederson Device because we never really saw anything like this come up in a developmental cycle ever again, and I was wondering if it being officially adopted and used in combat might change development. Would it be quickly done away with after the war? or would dual rifle-pistol caliber weapons become standard (We know there were devices developed for the M1917, SMLE and Mosin). potentially slowing down the procurement and adoption of semi-automatic weapons.

Secondly would be the Thompson SMG (Then known as the 'Annihilator) If it were to be used in combat, would that speed up western adoption of the Submachine gun into the military? Instead of having to mass purchase them in the beginning days of WWII?

Idk, just a cool thought experiment