Guys,
This is really an interesting question. Here are some engineering figures from materials as we know them today. What brass/bronze was originally used - I don't know.
Wrought Iron Bar ASTM A189 (The original barrel material)
UTS 48,000 to 54,000 psi
YS 30,000 to 32,000 psi
Elongation 25%
12L14 leaded steel ASTM A108 A29 (What we use today)
UTS 78,000 psi
YS 60,000 psi
Elongation 10%
Naval Brass Alloy 464 (Ezra says Ed Rayl uses this)
UTS 75,000 psi
YS 53,000 psi
Elongation 20%