It's been a while since anyone posted here, so I guess it's time to get something up. In keeping with my reputation of being a source of aggravation, here goes.
Got the Revell Gato, but want to do a Guppy? Love the Guppys, but really keep the 5"/25 gun?
What do you think of a Guppy with a 5" gun? Unrealistic? Never happened? Not so fast.
USS Argonaut (SS-475) was a Tench, Fleet Snorkel conversion, with a Portsmouth sail. And 5"/25 on her after deck.
She retained, this configuration, into the early 50s, and, possibly, as late as the mid 60s.
In 68 she was transferred to Canada.
Did she keep her gun? I don't know. I can't find any pictures with the gun on her.
I did find one small picture, (supposedly) of her, with a North Atlantic sail and a lump on the after deck that could be the 5 incher.
Once again, when it comes to US diesel boat, if you can imagine it, it may have existed.
However, I might hesitate to mount a 40mm on the sail of a Guppy. But a 50cal, on either side of the bridge, would be OK for most Guppys. Most had a pair of 50s, stowed below, and mounting points were located on either side of the bridge.
Mike K.