Big Calibre is a 1935 American Western film produced by Supreme Pictures and directed by Robert N.

[1] The film features Bob Steele as Bob O'Neill, a stockgrower who, seeking vengeance for his murdered father, goes after the murderer, crazed scientist Otto Zenz (Bill Quinn).

Rancher Bob O'Neill's father is gassed to death by lunatic Otto Zenz.

In a bid to avenge his father, Bob tracks the scientist down, and they eventually have a showdown in the dry plains.

[2] Film critic Bob Magers considers Big Calibre to be one of Steele's finer films.