In the British standards we have both Large Fowl Silkies and Bantam Silkies (there is also 'regular' Silkies that are in between and don't fit either class).
Bantam are around half the size of your standard Chicken whereas the Large Fowl are pretty big.
At my last show I saw a Large Fowl Silkie Cockerel that was the same size as my Large Fowl Light Sussex cockerel. I never knew Silkies could be so big.
Due to where you are located, I believe there is mainly just Silkie Bantams were you live, so your birds size could be due to cross breeding/poor breeding.?
Regardless, I still think he is lovely!