so it's not out of the realm of possibility that a GI, even one with no particular spec ops training, would know what a "hush puppy" referred to.
But still, sort a silly guess as to what sort of pistol a random G.I. would have been issued in Vietnam? Unless the whole point of the question was to gauge the guy's response? Maybe the detective wanted to see if the guy actually knew anything about weapons of the era, and if he'd said, "What's a Hush Puppy?", then the detective (this particular detective appears to know just about everything about everything, from baseball statistics, to botany) would know he was dealing with a guy who didn't know much about weapons?
If the guy were a WWII vet, and the detective said, "Were you issued a suppressed High Standard .22?", I'd have the same reaction; SOME people were issued such a gun, but it would be a totally left-field guess as to what a common soldier, or even a very uncommon soldier, would have ever been issued during WWII.