This illustration shows just how fast the transformation from Bruce to Hulk can happen. From the barrel of the gun to hitting a target about, what? 15/20 feet away? A bullet’s muzzle velocity is between 1200 to 2800 mph. So, this bullet would take on average about 0.01 seconds to travel that distance. That’s a quick morph! Especially considering the clothes he is wearing changes with him.
Ratchet's Hulk Collection 