Rockford had a snubby revolver he kept in his sugar canister, not a 1911. A S&W Chiefs Special I think.
Didn't watch the series, but I do remember reading a few of the books when I was a wee lad. Mostly it seemed they got caught snooping around a lot and the cops came to rescue them when one of them or their "chums" got word to the Chief. I do recall one where they went camping and their Daddy presented them with shiny new .22 rifles. If I remember correctly they actually used them to threaten the bad guys into surrender.