Could either gun calibre disable a submarine?

Could both 4-inch and 6-inch guns disable a submarine?

Yes. Twin 4-inch guns were preferred for their higher volume of fire and greater chance of hitting from a platform below 2,000 tons.

Both calibres could inflict enough damage to disable a submarine. For a platform below 2,000 tons using 1930s technology, twin 4-inch guns offered a higher volume of fire than a single 6-inch gun. That increased the chance of hitting the target. Hand loading supported the higher rate of fire, and damage to the pressure hull was enough to stop a submarine operating.