@harryexplorer: I thought the same thing at first, but the kana is コンストラクション and you can even see the name Romanized on pg 30 of the chapter. I did a bit of research trying to find a real-life ship called the "Construction", but I didn't find anything. Apparently, it's just a fictional ship which seems to be heavily based off of the U.S.S. Constitution in both how it's built and length of service.
As for the gun, that .577 caliber looks cool, and I guess it would've been cooler if he had used an actual rare gun from the time period like that.
Although, correct me if I'm wrong, but wasn't the Bland-Pryse an English gun, manufactured in small quantities in England?
I suppose maybe Tiger could've imported one in the narrative, but maybe the author didn't think someone in that era would have done-so, or just wanted something a bit more custom and one-of-a-kind?
I generally agree with you, though, Tiger's gun is a bit weirdly overpowered.