At the age of thirteen I started shooting a Parker Trojan 12 ga. I never measured the chamber length, I just shot what I could buy at Western Auto or any hardware store within bicycle riding distance. The 12 ga. Trojan is built on a 2-frame and when I shot "Duck and Pheasant" loads that old gun never so much as wimpered - it just belched out a payload of #6's and set this boy back a step or two. I guess it must have had 2 5/8" or 2 9/16 chambers... heck, we never gave such a thing a second thought and I'm pretty sure that was the mindset back then... after all, they weren't those dangerous "Damascus or Twist" barrels...