At Close Quarters: Skirmish rules for the 20th and early 21st centuries. More modern warfare than WWII. When a Corner of Hell came out, Chris revised At Close Quarters to represent more modern and very near future.
A Corner of Hell: Skirmish rules for World War II, based on the "At Close Quarters" system. Contains selected platoon organizations.
So, yes, they use the same mechanics. At Close Quarters is based on units. Both use a d6 and d20.