The animal channel claims that the Silverback Gorilla is stronger than a Grizzly Bear. The show mentioned that a large male silverback has strength to bench press 4600 pounds.
It makes sense. Gorilla have been around a long time in Africa. They must be able to defend against lions and other big animals.
It takes 6 grown men to control 1 male chimp. It looks like it would take 16 men that can bench press 300 pounds to take on 1 silverback gorilla.