How often did they use deck guns?

[YonMaruIchi]

Hey community, long time lurker with a simple history question.

How often did the American skippers use their deck guns throughout the war? If they found a lone cargo ship in calm waters would they always use it? Because early on in the campaign in SH4 it seems like there's really no reason to use torpedoes at all whenever you find a lone merchant ship with no defensive guns on it. Heck on I'm my third patrol and I just sank two medium sized cargo ships traveling together with no deck guns of their own before planes came to save them. I know they get more guns later in the war but for now there's not many reasons to use torpedoes if I find a loner.

Also did historical skippers focus more on hunting down convoys or sitting on routes where lone ships would always pass? Because the latter seems a lot easier for racking up tonnage. I want to adjust my playstyle this time to feel historic, but I haven't read enough books unfortunately. What do you guys do?

Thanks in advance!