I have took a few pics and some electronic scales .. and done a few comparisons ..
Test subjects
S&W M36 3 inch barrel
S&W M10 3 inch barrel
Ruger SP101 2.25 inch barrel
Charter Bulldog 2.5 inch 44 Special
Weights
Charter Arms weight 22 oz
S&W 36 weight 23 oz
S&W 10 weight 32 oz
Ruger SP101 weight 25 oz
To me the SP101 and Charter are close in size .. The Charter is a bit lighter but the 5 holes of the 44 are bigger than the SP101 holes .
The Charter Bulldog frame would be really close to the Colt "D" size frame.
Hope this helps anyone who is wondering..