There is something wrong with the description of the Condon rifle, the first one Dennis listed. A 37" barrel of .54 caliber 1.5" across the flats at the muzzle that weighs 11 1/4 pounds.
It got little use because nobody could carry a rifle that big around for long. So, 1.5 inches at muzzle, why would anyone order that in the day for hunting?
Either the 1.5" barrel size, or the weight, is a typo.
A quick 'search' shows a piece of octagon steel with a .50 cal hole in the center weighs about 6+ pounds per foot, so a 37 inch long barrel would weigh a bit more than 18 pounds. And if you look at the pictures showing the sights, comparing their size to that of the barrel, either the sights are absolutely gigantic, or the barrel is less than 1.5".
Of course, I guess if the barrel is about 3/4" at the breech, the 11 1/4 pound weight might work out as well. It'd look sort of strange, but,,,
John