Thanks. Dave:
Your visual comparison seemingly indicating the same shape, etc of the ctg feed guide leaf spring fits with my experience that leaf springs can be just enough different in temper that even swapping correctly dimensioned ones might help.
The range of cocking effort produced by swapping original Spencer mainsprings is WIDE, to the point of being scary, to me. I have at fussed with at least twenty and had no way to anticipate what they will do until installed.
A friend is a quite successful BPCR shooter and uses modern Shiloh's, but found that ORIGINAL Sharps mainsprings helped him.
He acknowledged a wide range of cocking effort within original mainsprings and selects his based on cocking feel.
By the way, I know of nothing negative about Shiloh springs and use them with confidence!
My guess is that he wanted a different hammer fall for less disturbance/vibration.
Thanks for sharing. Helps us for sure.
Regards,
El Supremo/Kevin Tinny