I thought that was in "1941". Dan Ackroyd's character telling the hapless
homeowner what "not" to do with the anti-aircraft gun the Army was
positioning on his property.
Scott Wilson

On 25-May-2006, Mark Hansen wrote:

That reminds me of the movie "The Russians are coming, the Russians are
coming!"
"... do not, under any circumstances, insert the ammunition magazine into
the
mechanism ... and never move this lever to its full forward position to
lock
the magazine in place ..." ;-)