Different elastic tension?
http://daggy.name/carillon/batmbook/chapter5.htmEvery solid body has a certain degree of elastic tension which, together with its density, determines the velocity of longitudinal vibrations running through it. This is expressed as V = (E/D)˝, in which V represents the velocity of longitudinal waves (in effect, the speed of sound through the material), E is Young's Modulus, or elastic tension in a solid, and D is the density value (mass per unit of volume). Using this formula, the speed of sound in a given solid V is obtained as a figure equal to the square root of the quantity produced by dividing Young's Modulus E by the density of the mass D. Therefore, the longitudinal vibrations in metal are proportional to the square root of the metal's elastic tension and inversely proportional to the square root of its density. All other modes of vibration in the material are correspondingly proportional to the longitudinal rate.
The steel is pattern welded barrels was very low in carbon; AISI 1002 - 1005 low alloy "mild" steel.
“Gun Steels” in 1891
https://books.google.com/books?id=-c8xAAAAMAAJ&pg=PA196&dq .......Witten....Whitworth.....Vickers
C......0.47.......0.30 - .42.....0.24 - .27
Mn.....0.41......0.24 - .31.....0.22 - .23
