I just spoke to the builder again.

She said the 54 caliber barrel will be heavier than the 50 caliber. The barrel is a Rice swamped 38" barrel. With a 1in66 twist.

According to the builder the Rice used for the 50 caiber is a 7/8" barrel. And the one used for the 54 caliber is a 15-16" barrel. And when weighed in comparison the 54 caliber is slighlty heavier than the 50 caliber.

The lock is a Large Siler. Tom.