Why does the smaller caliber weigh more than the larger one?
Within any one model, the outside of the barrel is a single fixed profile, the same octagon and contour whatever the caliber. The only thing that changes from one caliber to the next is how much steel gets bored out of the middle. A smaller bore leaves more steel in the barrel, so that rifle comes out heavier. A larger bore removes more steel, so it finishes lighter. On the J.K. Hawken, a .45 runs about 8 1/2 pounds while a .58 comes in around 7 1/2. If you want more weight out front to steady your hold, lean toward the smaller calibers. If you want the lightest carry, go larger. It is also why the Hawken barrels are interchangeable, since the outer dimensions stay the same across calibers.