The 7.5in/50 gun

The 7.5in gun seems like a very "pre-Dreadnought" caliber. I just designed a gun that is a 7.5in/50 gun weighing 18.75 tons. That would be the weight without the breech. I've gone ahead and used the standard shot weight of 200 lbs. The muzzle velocity is 2,948 ft/sec. That is sufficient to do a good bit of damage at relatively close range. The shot would rapidly lose velocity, as the shot is only 0.474 of the cube of the shot diameter in inches (a useful empirical relationship). A better shot weight would be at least 210 lbs or greater. 210 lbs is about 0.5 of the cube of the gun caliber. A really heavy shot would be 240 lbs (similar to the 15in/42 shot).