The forward assist was made to shove the bolt into battery in the event the rifle fails to chamber during normal operation. Alot of men died so that little device was invented. Ckeaning kits were also issued for the first time to keep the weapons free of fouling. In a real combat situation, cleanliness means reliability.
Barrel fouling really only affects accuracy. Its important to shoot several rounds through a clean barrel before putting it in the safe. You will most likely not take a shot on a warm barrel when it counts. Fouling helps keep the cold "fliers" from getting away too much.
