I never really felt over-gunned shooting mule deer(bucks) with a 300 WSM. Inside of 200 yards I would say a 223 will knock one down fairly easily on most shots. At 400 yards a 300 WSM will have more thump.
Never hit any big game yet in a vehicle(knock on wood).
Hit a cow on a 4-wheeler and bent/cracked some chit last fall but she ran off unscathed. Wasn't even our cow...
