Also I see the Chaparral 1866 advertised as a color case hardened receiver. Isn't that really just a 1873? If not, what makes it an 1866 if it is not a brass frame?
I'm sure others will chime in here with more and better information, particularly as regards the Chaparral rifles. My comments are more general in nature. A CCH receiver would truly make it
not to be a "true" 1866, but it wouldn't automatically make it a '73.
Though they are similar, the '66 and the '73 have several key design differences in addition to the brass frame. First, the side plates are different -- the '73 is easier to disassemble and clean. Second, the '73 has a safety interlock that prevents firing if the lever isn't completely closed -- the '66 doesn't. Third, though I'm not entirely certain here, the angle of the stock in relation to the barrel is different.