Depends on how you define the word "gun". The largest ever built in terms of how wide the inside of the barrel is- would be a mortar built by the US in WW 2, known as Little David. It fired a shell that was 36 inches wide, and the shell weighed more than a ton and a half. Little David weighed 40 tons, and is located at the museum at Aberdeen Proving Grounds.
The biggest gun is a SPG gun the Monster which is a german rail gun mounts a 800mm mortar
The Russians fit 125mm smoothbore cannons to their tanks. The NATO countries like 120mm cannons.
The Paris gun made by the Germans in WWI.
NO, biggest is an adjective; the superlative form of big (big, bigger, biggest).
Oklahoma has the biggest, followed by Dallas, IIRC
A Siberian Tiger is the biggest big cat
The adjective 'biggest' is the superlative form for the adjective 'big': big, bigger, biggest
desert eagle
big
The biggest "big" cat is the Siberian Tiger.
The Railway gun the Germans used to shell Paris in WWII
New Zealands biggest rock is a beach rock they can be as big as a big big super big mountin