Actually most other countries didnt fight war on the frozen side of the chinese and russian wastelands ,where frozen dust often had 50% of rifle inoperable,at times. Also lots of countries had action covers even the US ,03 you guys love so much,LOL.but they didnt build it right into the rifle like the japanese did,tho I think (and I have been wrong on occassion) that the brits and the french played with designs to keep sand out of actions..also if you look at modern issue weapons, a large percentage incorperate a "dustcover into the design, for rifles and machineguns(including the M-16). long as there have been longarms,there have been ideas for how to keep them free of dirt ,snow and mud