Is this a .60 calibre gun?
Yes, this is a .60 calibre (bloody Brits
) TOY.
Sorry, I cannot in good conscience call this a weapon, or even a gun. Both of those words describe a tool that is good for the purpose of sending some kind of projectile downrange- even when used in the 'this is my rifle, this is my gun' context from Full Metal Jacket.
They describe something useful, that has practical applications in the real world.
This is a TOY- something built for fun that has little or no value in realistic use.
It was simply done to make a really cool post on a gun forum.
If you need anything bigger than a .475 Linebaugh to kill it, then God didn't intend for it to die an unnatural death.